Hi Reddit. I'm Seth Horowitz, neuroscientist, author of "The Universal Sense: How Hearing Shapes the Mind," sound designer, science consultant for TV & film, 3D printing (for science!) afficinado. AMA!

I don't know if you can answer this, but...

I have real issues if there are too many sounds from too many places at once.

So, for example, if the TV is on, the kids are making noises, the dishwasher is running, and my wife is trying to talk to me, I'll go nuts. The frustration builds and it takes real work to remain calm.

The same issues occur in malls and pretty much any place chaotic.

The VA says it's a result of my time in the Gulf and adderall HUGELY helps.

Do you have any familiarity with this type of thing and if so, do you have any suggestions?

You're describing misophonia and it's not that uncommon, but when you mentioned your service record, well it's even more common. PTSD (which is sometimes treated with adderall) and other mindstates that have a high level of arousal shift your attentional threshold, making you more prone to startling, even if familiar environments. I had a luckily brief run in with it a decade ago after a very bad experience with search and rescue and found that even if I didn't show the classic startle behavior, almost every sound grabbed my attention and it drove me crazier (as well as severely impacted my sleep).

Two suggestions. First go and get a comprehensive hearing and vestibular function test. A REALLY comprehensive one. A lot of military personnel suffered subclinical hearing and vestibular damage. Your brain will often try and overcompensate for a damaged area in your hearing (which is the basis for some forms of tinnitus) and hence up the gain, making normal sounds seem uncomfortably loud. But subclinical damage to the other half of your inner ear, the vestibular part, can be an underlying cause of many PTSD symptoms including emotional responses to events. The vestibular system is deeply tied to basic emotional and arousal areas of the brain (think fear of falling, panic attacks linking to vertigo, the high of a high speed motorcycle ride or base jumping). Since you don't regenerate hair cells in either part of your ear, these symptoms can last a lifetime and of course get worse as we naturally lose high end hearing as we age.

Next, after you get your exams (or even before) check out misophonia support groups and see if you can get a referral to a local physician/audiologist who works with the condition. http://misophonia.com/ isn't bad although some of the links for resources they provide are a bit fluffy IMHO. Hope this helps.

I can't thank you enough for your response.

1. The VA says PTSD.

2. I have tinnitus.

3. I had a hearing test that was the normal one (passed), but my wife just told me this morning that I have another one tomorrow.

4. I was in Military Intelligence, specifically SIGINT / CEWI. We did direction finding on target communications, so we sat all day with headphones on, scanning freqs.

If there were anything I could change about myself, this would be it. It's unbelievable that I can go nuts doing very normal things.

I'll check into it -- again, can't thank you enough.

Yup, wearing headphones all day, especially with sudden squawks can cause all sorts of problems and usually not diagnosed until it's too late. When you go for your next test, definitely mention misophonia and try and schedule a vestibular assay and be firm (not obnoxious, but don't let them wave you off). Fingers crossed for you...

Do you think there is any true scientific data on Bi-Neural Beats? If so, what are your thoughts on this phenomenon?

EDIT: Spelling

Binaural beats are a fascinating phenomenon and studies have shown that they can be picked up all the way through the cortex, even though they are a virtual phenomenon (decent paper here - http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2741401/). Howevre, what I found with years of playing with them is that simple binaural beats don't have much psychological effect unless there is a lot of expectation by the user. I developed a technique with my sound design company for making spectrally rich binaurally beats (basically you create a music or sound track limited to under 3 kHz, which is about the upper limit for the temporal comparison and encoding in the superior olive that triggers binaural beats, and then do a sliding shift of the other channel to separate the frequencies in the two ears by the beat frequency. It seems to grab a lot more cortical processing and I've used it in sleep induction algorithms that are being used commercially.

Wow! Thank you so much for answering! -i have no idea what any of what i just read means....

Okay, simpler (sorry - my bad for still talking like a professor) - binaural beats are generated by your brain trying to take two frequencies presented to each ear that are too close to distinguish and turn them into a single thing. That thing is a sound that wobbles or gets louder and softer at the difference between the two tones in each ear. The rate at which the beating occurs is encoded throughout the brain, but single beats don't do much unless you'r really wanting them to. But there are ways to use complex sounds to get that beating rate to grab a lot of your brain and change its behavior.

What is the most interesting experiment you have conducted with an animal, that had an entirely different outcome than you expected?

My absolute favorite experiment was one that sadly never got published due to a lot of factors but I still hope to carry it out one day. I've always loved working with bats and got interested early on in how they balance while flying at 30 mph (and eating and dogfighting) in total darkness. I published a basic paper on how they use their echolocation to calibrate their vestibular (balance) system the way we use our eyes and priorioception but it focused on echolocation more than balance. The next step though was trying to figure out which way their heads aimed when they were flying. IR cameras (which we used for flight work) tend to have lousy resolution and relatively low frame rates. So I realized if we could mount a tiny laser on their heads with a crosshair pattern lens, we could figure out exactly where their heads were pointing and reconstruct their vestibular function by combining body position and head aim. So I (and the engineer who was one of my favorite people) used a 3D printer to make tiny backpacks, disassembled some laser pointers, attached rechargeable lithium ion batteries and weighed the whole mess. 4 grams. bats can easily lift half their body weight (big born bats weight about 18 grams), so I stuck it to them using toupee tape and was able to get normal flight behavior with a red crosshair skittering across the walls showing where their heads were aiming. tl;dr - bats with frikkin' lasers on their heads. And I got to use that as a title for my presentation at NASA.

Holy crap that is fricken sweet. This has to be one of the most detailed, interesting and complete IAMAs ever. Thanks Seth.

So far it's been a lot of fun for me too - I love reading AMAs although I always seem to arrive too late to the party to contribute so thought I'd try it. Unless of course you want to talk about the movie Rampart...

Can you please post some pictures of the bat-packs?

Hard to see the actual pack (it's quite tiny) but here's a picture of one of the bats carrying the laserpack (sorry about the blurriness - hard to focus on him - couldn't use full illumination because it upsets the bats)

twitter.com/SethSHorowitz/status/335114274399731712/photo/1

Hi and thank you for doing the post. I have a question in regard to Autism and sound. I understand that there is a room where sound is completely blocked out, has any studies been carried out in regard to the effect that sound and vibration has on autism. I hope my question makes sense?

Anechoic rooms are pretty common in acoustics research, speaker design and analysis engineering as well as when working with sound-sensitive animals, but they are not fun to spend much time in. Your ears and brain start searching for sound, eventually lock on to your own heartbeat and breathing and it gets freaky pretty quickly.

As per autism; the field is frankly a mess. Definitions and diagnoses are all over the place. But for those who are pretty firmly on the autism spectrum, sensory problems are common, both oversensitivity to sound and lack of reaction. I've been working with some people trying to come up with sound-based aids for some autism conditions, ranging from white-noise blockade to using structured sound to increase focus on tasks, but it's very tough going. But one of the features that I find interesting in severe autism that seems to get ignored is the rocking behavior. Rocking behavior is a way for your vestibular system to induce relaxation and even trigger entrance to sleep (it's called Sopite syndrome - non nauseogenic motion sickness), so I suspect autists who show this behavior are trying to use their vestibular system to swamp out their other sensory systems so they can relax.

I really wish i could answer more clearly but it's a tough field and I'm just looking into it now.

Thank you for taking the time to answer and keeping it understandable. :-) I ask because, when my children were younger and at school, one of their friends brother was autistic. He was generally unresponsive and isolated when it came to interactions. However, the first time that I stopped to talk to his mother, he grabbed my hand and clung to me. When I stopped talking, he would clench my hand and start shaking it from side to side until I started talking again. At the time it just seemed like he was acting up and had found a friend. As time passed, we came to realize he liked the sound of my voice and so I would talk to him constantly whenever I saw them. ( No miracle voice ) It just interested me in the quality of sound and peoples reactions. Just a further question in regard to the vestibular system. Could an uneven vibrational event across the inner ear and cochlear create a confusion in the brain causing a loss of spatial awareness and that the rocking is an attempt to rectify that event?

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That's a really good idea.

That is a fascinating story. People have favorite sounds and it sounds like your voice was his.

Loss of spatial awareness (which I'm translating to mean orientation awareness) at a vestibular level almost always leads to vertigo, falling down and panic attacks, so it's unlikely that the rocking is to correct for that. In a very simplified description (and it's not well researched) rocking behavior specially in the front/back or sagittal plane sends output from the sacculus (the vertical axis or gravity sensing inner ear organ) and the vertical semicircular canals (which measure rotation - given their orientation mostly a pitch/roll combination) through several of the vestibular nuclei in the brainstem at the same time. The complex periodic input may swamp arousal regions in the brain (also called the reticular activating system), basically overriding any other input coming in, and leading to calming down and in some cases sleep.

Can you break down the science of synesthesia to laymen's terms?

How much time do you have? I'm actually devoting a chapter on it in my next book (if the publisher decides to bite). True synaesthesia is relatively rare, although you’d never know if from reading popular accounts especially given the highly variable diagnostic criteria used. The short version is that it’s an involuntary and automatic condition where one sense bleeds into another in a highly spatially selective way, assigning sound to color or colors to text, often with exaggerated memory and emotional responses. Neurological and genetic hypotheses abound, including reduced inhibitory responses in areas responsible for sensory processing, global changes in areas responsible for sensory integration, and even rather fluffy supposed relationships with mental illness or autism. However, categorization of synaesthesia as a diagnosis rather than as part of normal brain variation may be more of a cultural artifact of our love for labels. What’s telling is looking at who gets diagnosed as a synaesthete – David Hockney, Vassily Kandisnky, Itzhak Perlman, Richard Feynman, and Nicola Tesla – artists, musicians and scientists with high levels of experimentalism and creativity. Are their brains actually different? Or are they just people whose brains mix sensation, attention and memory at the farther end of the normal spectrum?

According to the textbooks, our senses are supposed to respond in a very specific way to stimulation, following the “laws of specific energy.” Photoreceptors respond to photons, the ear’s inner hair cells respond to pressure waves, the olfactory epithelium and taste receptors respond to chemicals, touch receptors respond to pressure (or hot or cold) and the vestibular sense responds to acceleration of the head. The problem is it’s pretty easy to demonstrate how you can trick one sense to respond to a different type of input. Close your eyes in a dark room and press (gently please) on your eyeballs. You’ll see a series of concentric arcs or rings, usually in an odd afterimage-like purple-green or yellow. So you just saw something based on pressure, something you’re only supposed to do by light. Or go into a club, somewhere where the bass throbs and the beat makes you move. Why are you moving to the beat even if you’re not a dancing fool? Because loud, low frequency sounds can shake the tiny organs in the vestibular part of your ear. Even though it’s sound, it can trigger vestibular reflexes that help you stabilize your body against the pull of gravity, making you tap your feet or at least shift your body side to side.

At some level we are all synaesthetes; we talk about tone “color,” describe musical pitches spatially as “up or down,” and describe things we don’t like by saying it “stinks” or “leaves a bad taste” in our mouths.  But those who take it to an extreme, transitioning from metaphor to simile, may be people who use the connectivity between the senses, attention and memory in different ways, yielding intellectual and artistic creativity.  

Whoa. Awesome answer!

The biggest gap I have with all of my private students is to get rid of negative and positive terms when describing a sound ie. "They have a bad sound". Instead try to put thought into the sound more than regurgitation of what their band director said. How does a sound differ from trombone to piano? Is one bad vs good? How about piano to piano? It's that use of trying to put a tangible label to something intangible.

I'll definitely incorporate your answer into some future teachings. If you're ever in the Louisiana area, this could be good Scotch conversation.

Okay first Maccallan's on you. Try and teach them about consonance and dissonance - at least there is a physics and biological basis to it. I spend a lot of time on that subject in the book and try and use it to point out that good and bad are such high level labels that they have very little meaning for anyone aside from yourself when it comes to sound.

... So, how DOES hearing shape the mind? I think sound can be incredibly ethereal and I think the ability to hear is a pretty underrated sense (although they're all really amazing)

Well, there's not much chance I can answer that quickly - my book could have easily been three times longer but my editor saved everyone ("we want people to read it, not use it as a structural support."). And I agree - hearing is severely underrated. I always felt I'd rather be blind that deaf. Being blind would be a serious pain in the butt. Being deaf would be lonely as hell.

Shortest version - you are surrounded by sound. It goes on around you, out of line of sight, in total darkness and is the only sense that's still running even when you are asleep. It's your evolutionary alarm system, keeping you safe when you can't see what's sneaking up on you. It's also the fastest sense, 4-20 times faster than vision (depending on what you're measuring) and doesn't require a lot of your brain to process it. So sound tends to get into your brain very quickly and provide an underlying context for everything else you sense and do in your life, even if you're not paying any attention to it. Hearing has shaped our evolution as mammals (members of the high frequency club) and our evolutionary jumps past the basic primate model with speech and music.

I got my neuroscience start in an auditory lab doing extracellular recordings in awake bats!

Do you have any specific thoughts on "smounds" and do you think it's time for basic sensory research to start focusing more on interactions between different modalities?

Where did you work? I think I know or knew all the players...

I heard the term while doing some research for my next book (on multisensory integration) and never really thought about putting those two senses together, but at some level it makes sense. Both are based strongly on temporal coding in the brain, although smell is working at about 1/20 the speed of hearing. I know that Belkin et al did a paper on it (http://pss.sagepub.com/content/8/4/340), but I haven't worked my way through the to read pile to get to it yet.

I absolutely thing it's time to start looking at how we build our umwelt, the world built from our senses. I think neuroscience's history, looking at individual senses, basic mechanisms, has been building up to us being able to start putting it all together. It's going to be an increasingly rich field over the next few decades. I was luck enough to get my degree just when it was starting in the late 90s so got to looking at integration of hearing, vestibular and lateral line in underwater vertebrates, hearing and balance in humans and bats, but I think it will become a huge area very soon.

Hi Seth. I want to ask you about something I've read called "musical frisson", that's when we listen a song that hit some emotional nerve and causes a physical reaction, like sweat, chills, tears or a smile. Could you explain that to me? Because everything I've read is really superficial and don't explain too much of the science behind it. Thanks for the AMA!

Know the phenomenon well; there are a lot of explanations, mostly centering around the release of dopamine from the reward circuits in the brain after a sensory input with positive valence (same thing from scratching an itch). Robert Zatorre who is one of the big players in the music and th emind field at McGill did a nice combined fMRI/PET study showing increased dopamine release following enjoyable vs neutral music (http://www.sciencedaily.com/releases/2011/01/110112111117.htm). However, I have a feeling that's not going to be a long term valid explanation. First, fMRI is a very slow and temporally imprecise system. It makes pretty pictures of living brains and has a huge ooh-aaah factor but it's too slow to show what's really going on at the local neural level. It's also hard to get a really good baseline emotional reaction in a tight tube with 100 dB clicks going off. In addition, dopamine does a LOT of things and some recent data indicates it's release is not so much a reward as a preparatory releaser for rewarding sensations. tl;dr - current thinking is it's a dopamine reward aspect, reality - it's never that simple.

Thanks for your answer. Is there any book or resource that goes deeper into this subject?

I go into it in my book to some degree (and I tried to orient it for th elay audience). If you want to go deeper, here are two professional articles on it (full free articles). Both are from Robert Zatorre's lab. They are not the easiest things to read but the intro and discussion sections should be helpful.

http://www.ncbi.nlm.nih.gov/pmc/articles/PMC58814/

http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2759002/

If "science consultant for TV & film" is a description for a real job, why does it always seem like science-related things are always portrayed so terribly incorrectly?

Great question because it's been a serious learning curve for me. It's almost never a "job" - filmmakers have their own hierarchy and language. It;'s about telling a story. Science consultants are usually brought in to help out with specific elements, either getting terminology right, figuring out what technological or scientific ideas are not going to generate hate mail from educated viewers, or even helping to figure out what kind of equipment might be useful in a scene. They are rarely the core of anything. There's also a huge difference based on how early you are brought into a project. With David Goyer's project, I just helped out in figuring out what kind of acoustic weapons might be possible in the future (even though I point out in my book that most contemporary acoustic weapons are severely over hyped). With the IMAX film and the pilot I'm working on with Natalie Chaidez, I got involved at the very beginning so I gather I'm having more of an influence. But science consultants are well outside the core of any show, so their advice can be taken or not. The filmmakers are the experts in their form of communication which is very different from that used in science. My take is that I'm not trying to make their science more accurate, but rather that I'm trying to use accurate science to make the show better.

If you want an excellent (although a bit academic) overview of it, read David Kirby's "Lab Coats in Hollywood." It's taught me a lot and kept my blood pressure down on occasion.

I see. That does make a bit of sense. I guess it's just Hollywood's way, to just ignore the logic behind almost any given subject in lieu of what they're imagining. Thanks for the answer!

One more question if you don't mind: What are some of your favorite subreddits to peruse on your alternate account?

r/Askscience, r/3D printing, r/books, r/IAMA, but I scan all over the place, looking for the occasional /r/WTF about a bat stuck in someone's toilet...

So, when the directors consult, is their primary intention avoiding hatemail? They certainty don't seem to care much about avoiding looking foolish. If that's the case I've got to ask, what level of scientific inaccuracy does it take garner hatemail?

I learned that their primary concern is being true to their particular artistic vision. A director who understands the fact that accurate science can improve the story will use it. A director who doesn't see the advantage wont' bother or will ignore a consultant or not bother hiring one. Kubrick brought in every heavyweight he could find for 2001. It gave the movie a 'realistic" vibe that we still buy into watching it today even though a lot of the details are wrong. He used science to make the story stronger (he even brought in the Leakeys to consult on the opening with the early hominids). But because the movie was so striking and seemed so accurate, it inspired a lot of people who were kids then to become the scientists who are now working at NASA. Movies and media (including TV, music, art) inform our culture, good ones inspire us emotionally. Those emotions drive most of our behavior, even if its to go into something as intellectual as science or engineering.

Re: the level of scientific inaccuracy, think about Armageddon vs Deep Impact. Michael Bay actually got NASA to sign off and help out with a lot for Armageddon even though scientifically it's a nightmare. A colleague of mine uses it as a "bad science" example in his planetary geology course. But it was very action oriented, very exciting and the look and feel is very NASA-ey and NASA relies very heavily on public perception and support since they are so woefully underfunded, so they sucked it up. On the other hand, Deep Impact was pretty damn accurate scientifically, much better acted in terms of realism. It also used a lot of NASA support (even hiring some former NASA personnel). But the bottom line? Armageddon grossed $201MM. Deep Impact $140MM.

People go to movies to be entertained. Sometimes that requires bad physics. If you're going to be a science consultant for movies or media, you do your best but have to realize it's THEIR show.

wow. thats one heck of a resume.u do a lot of things. :) no questions. just saying youre awesome.

Thanks - I can't stand being bored so I end up doing new stuff all the time. Whatever I do it's usually noisy. Luckily my wife is a sound and biomimetic artist so her stuff is just as noisy as mine.

Do you think that the increased level of stimulation from living in a city (being constantly surrounded by different sound sources) impacts behavior or development in an appreciable way?

Absolutely. As I mentioned above (below? don't know where it will end up), you are really good at setting a baseline of "normal." In a loud city with a lot of nighttime illumination, constant smells from food or trash or exhaust, vibration from traffic, most people will still just go on thinking everything is fine. The problem is that while your brain will turn down the attentional gain on all this stimulation, at a physics level, it is still getting in there, interrupting sleep, wearing out your hair cells, constantly stimulating your vestibular system (which can elevate blood pressure, shift your mood). And kids are much more sensitive to stimulation; young children in particular have not developed a lot of attentional control and sensory modulation systems and what can happen is that if they are raised in a very noisy environment (enriched is good - noisy is bad), they will actually down-regulate these systems which can affect their performance later in life. This is NOT a guarantee for all kids or adults - there is a lot of genetic and developmental variation and even things like having carpets on floors and drapes over windows can significantly decrease noise. But in general, being aware of your environment, trying to actively control stimulation that is out of your control, can improve your hearnig, physical and emotional health a lot.

What do you mean by "the universal sense" considering that hearing loss affects about 10% of the global population?

Actually hearing loss affects more like 30% of the global population and it gets worse as we get older. Presbycusis (age-related hearing loss) is a universal feature in all studied mammals, although one thing I'm fascinated by is the fact that bats still hear high frequencies even though they live abnormally long times.

But I call it "the universal sense" because there are no normally deaf vertebrates. There are blind ones, ones with limited smell, taste and touch and lots of senses that we don't experience without technology. But everything with a backbone that has not suffered a physical, developmental or genetic accident hears. Sadly we often don't appreciate it until something goes dreadfully wrong.

From working with both Dolphins and Primates did you gain an appreciation of just how intelligent those animals are? Also what kind of experiments and research can you do with more intelligent animals, that you just can't with standard research subjects such as mice and rats?

The question of intelligence is a problematic one for me. I've seen bullfrogs figure out problems and knew a dolphin who was so dumb he couldn't pass tests that rats passed easily (poor Toby). The problem is asking what intelligence is. Never seen a good definition that can encompass all the variations in vertebrate brains. I try and look at behavioral flexibility and complexity especially in the face of a novel situation, but then you have the problem of animals that are novophilic (love new things are curious, like many primates and dolphins) vs novophobic (like rats and mice). Animals that show the greatest individual behavioral complexity tend to be novophilic, but they also tend to be high on their food chains and have less to be afraid of. If there was an "escape from the predator" intelligence test, I'm pretty sure every rat or mouse out there would kick my butt pretty quickly.

My overview, dolphins are hard to gauge because they are extremely social, emotionally accessible and will bond cross species. While definitely intelligent, it's a completely different form of intelligence than primate use. They can solve complex problems, can engage in complex emotional and communicative relationships with each other and humans, but we also color our perception of them because it's hard for us to get over that "smile" even though it's just a hydrodynamic feature and the fact that they will hang out with us. Even if you work with orcas who are definitely NOT warm and cuddly, we still respond to the oversized head, the panda-like coloration and the fact that even though they are scarier than any shark, they will not normally attack humans and will often come over and investigate us.

We also color primates with our perceptions. They look like us, act like us, have similar social structures, good and bad. This has led to a lot of really questionable studies in primate intelligence and cognition. A friend of mine was the research director for working with Koko, the signing gorilla, and her take was that Koko was not really a gorilla any more. She'd spent so much time among humans that because of apes ability to socially bond she was more like a "human spoiled brat."

You get the same issue when dealing with talking birds, like Alex, an African gray parrot who demonstrated an ability to manipulate human speech sounds into "speech" demonstrating that parrots can handle human grammatical and semantic structures. Again, while it is building off the animal's native neural resources, it's still trying to see "how human they can be" rather than how good they are at being an animal. A good example of this is a classic experiment carried out on ravens by Bernd Heinrich which demonstrated the problems in previous experiments expectations. There had been studies showing that if you took a piece of meat and tied it up with a string, male ravens would go over and untie the string and take the meat, but females wouldn't. This was seen as a difference in spatial reasoning between male and female ravens. In Heinrich's experiment, he had a male and a female in the cage together. When the female saw the meat, she cawed and the male went over and untied the meat and gave it to her. THAT was raven intelligence, linked to their normal social behavior.

As for animals like rats and mice (and bats and frogs), our ability to understand psychophysics (mapping the physics of sensation onto the psychological percepts of the mind) combined with understanding how animals learn (using both classical and operant conditioning), we can communicate with almost every living thing. But it's always hard to put ourselves in our subjects world and come up with the right way to get the information we want.

I've always been interested in synesthesia being related or compared to 'perfect pitch' - could you elaborate how some people seem to have perfect pitch because of a form of synesthesia?

There's a common problem with both perfect pitch (proper term "absolute pitch") and synesthesia. Both are "cool" things to have with a lot of media exposure, but the prevalence is really low for both. Also I don't think synesthesia would be a good "cause" for absolute pitch and here's why. People who really do have absolute pitch often show enhanced asymmetric development of a part of the brain called the "planum temporale" with the left side being normal sized but the right side being smaller than normal. This indicates that absolute pitch is NOT an enhanced sense but may rather be due to more limited processing of complex pitches. (One of the things that irritated me in some early studies on music perception in the brain was defining a "musician" as "someone with perfect pitch." That's a piano tuner, not a piano player).

On the other hand, no one really knows what the biological basis of synesthesia is, although there have been some data showing it can be cause by everything from enhanced cross connectivity or poor insulation between sensory tracts. People who show real synesthetic symptoms are often very creative and cross modal, which is sort of the opposite of what you'd get if you had absolute pitch. On the other hand, since we do have a VERY tight relationship between pitch perception and direction and spatial ability, someone who had excellent spatial perception and skills and a greater tendency towards sensory integration might show better than average relative pitch perception.

Shriek.............I've found you

I have my suspicions but I'm going to need more information to figure out who this is...

Out of all the professions you have been in, which was the most enjoyable? Also, are there any other professions you see yourself working in in the future? Thanks for the AMA.

My parents used to say I was a born a scientist and that if they ever got to lay down for five minutes I'd dissect them. But what I've found is that almost everything I've done in my life, sound played some central role in it, and so getting chops as an auditory/vestibular neuroscientist helped tie everything together. I'm currently taking a break from academia to work on my next book and some sound projects I've been stalling too long on, but I suspect I'll get back in that game eventually. My basement lab doesn't have enough room or potential sterility for some of the projects I want to work on.

Hi!! im an undergrad student at engineering, but i am working in the health sciences area and blessed with the oportunity to work in the neurosciences area, i was impressed with the "how" the brain works. Hopefully i will be able to study neurosciences and neuroimaging

What inspired you to pursue a neurosciences degree?

I'm one of those people who has been amazingly lucky in terms of having some great teachers. I was working as a dolphin volunteer trainer in the late 80s (without a degree) and just fell in love with dolphin behavior and communication. I tried to build a MIDI-based underwater keyboard for a communication experiment but it was unfortunately not as salt water proof as I hoped. At that point, I got tired of not being taken seriously because I didn't have a degree (took my 20s off to be a musician and animator) and went back to school for Psychology, figuring "eh it's BS, I'll finish fast." Then got tricked into loving biopsychology by one of my professors, Peter Moller, who is an electric fish god and was my undergrad mentor. Still in touch with him. he suggested I go study at Brown, so entered the psychology program at brown, studying how frogs learn to hear. (They basic theory was that tadpoles were deaf, but the experiments were all done with tadpoles pinned to a board in air. To me that woudl be like testing human hearing by shoving someone's head into a bathtub and asking them what they heard. I had to build an underwater electrophysiology rig but showed that tadpoles do in fact hear really well underwater.

About the time I was finishing my Masters in Psych, the department imploded due to personality conflicts among the faculty, but my advisor got me switched to the neuroscience department which was MUCH calmer and let me get work done. So while I was aiming for an animal behavior/biopsych degree, I got switched over and found that neuroscience has much cooler toys to play with, although I was still focusing on the same general area. But I still find myself defending psychology - even though it's not as 'cool" as neuroscience, it is the mother field for anything involving behavior - neuroscience, genetics, biomimetics.

Hello! I admire your work greatly. I am a person that solely relies on vision. I cannot process or retain auditory memory or cues (although I have perfect hearing). My question is - is it worth attempting to development auditory strength? I am especially talking about neural plasticity. Can I change the way my brain processes information? How?

Wow, that's a complex issue. Have you spoken at all with a neurologist to find out the basis? It could be a failure at a cortical level in an association region, it could be problems with attentional pathways, it could also be specific problems in your hearing curve. Talk to a professional and be as specific as possible. The short version is you can almost always compensate for deficits; your brain is incredibly plastic, but it is also incredibly complex. The problem with most people who try and overcome a complex cognitive/sensory issue is that they give up. It's HARD. While every sensation you have, every memory you call up, every action you take changes you brain at anatomical, biochemical and physiological levels, getting very specific results requires a lot of dedication and help with people who have experience with it. Just learning to change how you pay attention can be cripplingly difficult. Wish I could offer more specific advice, but all I can say is do keep trying and get as much help as you can.

Hi, I'm also a science aficionado (PhD student) and I think everyone should consider the info portrayed in the Zeitgeist Moving Forward documentary and by Jacque Fresco. Have you seen this information, if so, what do you think about it, if not, would you be willing to check it out?

Also, do you work at a research institution?

Haven't seen it, but just looked it up and will definitely check it out.

I was faculty at Brown until very recently, but am currently taking a break from academia. Science is great but I definitely needed a break from the politics. I'm beginning to miss it though so am beginning to sniff out positions again.

Hello! I mostly just wanted to let you know how awesome your work is--I worked in a bat lab during undergrad, myself. The possibilities for sound research are so exciting! I guess if I had to pick your brain, I'd like to know what your advice is for finding your niche as an aspiring scientist. There are so many things out there, I almost feel lost in all of it.

I took a very weird course in science, but it worked for me. I think the rule of thumb is figure out what is so interesting at a base level that you could give up several years (decades, a lifetime) to do nothing but study the basics of it. Don't go into a field thinking to become an expert. I still have days where I want to hit my head against a wall because of how little I know even in a field where people are calling me an expert. You have to choose a basic direction and then be willing to let it lead you. I had an incident in 2001 where my postdoc lab ran out of money and I was forced to move to a chronobiology lab which I was not happy about at first, but it turned out to be a fascinating side venture and let me find the linkage between the vestibular system and sleep. That let me work on an acoustic treatment for sleep that turned into a commercial application for a sound design firm that I started which applies neuroscience and psychology to music and media. Everything will contribute to your path; it just helps if you have an overall view of what you get passionate about. Because the pay sucks. ;)

And what do you think about the future of 3D printers? Do you think in the future people wouldn't need to work cause you can produce everything (food, clothes, houses) on the 3D and all you need is a delivery of building materials?

Not for a while. First, I love my 3D printer, but mostly because it's a technological model of genetics in operation: going from code to object. I just find that mindblowing to watch. I also find it useful for prototyping or making basic things or helping my wife use it for her my wife's art. And what can be done in the more precise larger printers is amazing, ranging from fine metal work to biocompatible organs. But it's still very time consuming and you have to have a lot of patience with them. I can print a teacup but it will take 6 hours and there's a good chance it will leak. I could send it out to have it printed in metal or ceramic but then it gets pretty expensive.

In about ten years, yes, they will be as common as iPads and capable of making basic household things and even food, but it won't be a panacea. At some point the legislators and lawyers are going to get involved and there will be screams of "physical piracy" as opposed to music or video piracy to keep you from printing those shoes you like. In twenty years, no one will even pay attention to them they will be so ubiquitous, but they'll also be very different from the 3D printers we see today. But I enjoy the hell out of them now.

Do have any recommendations for what to do upon graduating college with a neuroscience degree? Specifically, straight to grad school vs taking time off and doing research? Research powerhouses vs smaller grad schools?

I'm afraid of being miserable/poor throughout my twenties while I get a degree and then realizing that career path isn't going to make me happy for the rest of my life.

Well first decide what you love about neuroscience. What I found is that you're better off being poor and not miserable than being miserable and not poor. There are a huge number of directions you can go. If you're concerned about money, check into pharmaceutical firms. They often have decent entry level positions for people with bachelors degrees and will pay more than you'll see in grad school or even as a postdoc. Many of them will even help pay for grad school to get you an advanced degree if things work out. And there's nothing wrong with taking a break between college and grad school. I didn't get my PhD until I was 37.

If you decide to go the grad school route, the most critical thing is not where you go - it's WHO your advisor is. Find out who is doing work you think is cool and contact them. Don't worry if they're at MIT. There is outstanding research being done at very small schools and most scientists will always respond to an interested student. A good advisor will not only guide you through the rough spots but will also help you get your degree with as litle cost as possible and help you move on to establish your own research area. Just realize that grad school is rough, financially, intellectually and emotionally. You have to really be interested in what you are doing or its not worth it. And realize that getting a PhD does NOT have to mean you are locked into academia. There is a huge market for neuroscience these days in everything from marketing to health and wellness.

I know it sounds trite, but do what you love and the rest of the BS will be worth it. Neuroscience is absolutely the greatest human frontier - it ties into everything, so being part of it puts you in one of the most fascinating arenas humans have come up with to date.

Any relation to Vladimir Horowitz, the composer and pianist?

My father used to claim we were, but a bit of sleuthing showed that no, no relation. Pre-Ellis Island the name was Gurevich, which did turn out to mean I was related to a Russian whale scientist whose work I liked when I was a grad student.

What have you learned about the science behind nostalgia in relation to music?

Nostalgia is an emotional (usually positive) reaction to a memory. You're dealing with a series of highly complex and interrelated systems in the brain. Then throw music into the mix and you end up with a something that might just be a moments wistfulness in terms of behavior but dragged in tens of billions or neurons and a hundred to thousand times that many synapses, and not one of them labeled clearly. It's also highly personal. You and I could have both heard a song when we were kids and it makes you all happy and makes me want to throw something.

I went over this a bit in my book, but take, for example, christmas music. Christmas songs have been around for over 600 years, and the basic musical tradition of consonance and simple tempos repeated at seasonal intervals has created years’ worth of memory traces and emotional-auditory associations with holiday events. But there are caveats to even this seemingly innocent use of music to affect our emotions. If you hear “Santa Claus is coming to town” when you’re a kid, it becomes associated with the holidays, getting presents and general family cheer. When you get a bit older, it can act as a pleasant reminder of happy times past. But after a while, you hear the first few notes and your brain says “It’s that song again.” You tune it out. And it shortly becomes environmental noise, which is in fact a stressor more than an emotional conditioner.

The phrase “familiarity breeds contempt” has a certain neural basis. As anyone who has almost reflexively rolled their eyes while being forced to listen to “The 12 Days of Christmas,” over presentation of any stimulus often leads us to ignore it. While the idea of consonant music works in general at a population level, constant repetition begins triggering habituation*. Habituation is characterized by diminished responses to the same stimulus over multiple presentations. It also kicks in faster and last longer if the stimulus is repeated more rapidly (with a shorter interstimulus interval or ISI in neurospeak). So after you survive the holidays and have 9 months or so to recover from hearing Frosty the Snowman, Rudolph the Red Nosed Reindeer and other consonant offerings, when the season rolls around again, the first few times you hear these songs, it triggers nostalgia again, bringing on the holiday spirit, but as soon as the barrage of Christmas music gets going, so does habituation.

So tl;dr, nostalgia is a loop between memory and emotional circuits triggered by a familiar but not over-presented sensory stimulus.

How often in your job do you have to sort out the various definitions of "silence"?

Oy. Mostly I have to point out that unless you are in deep space at absolute zero there is no such thing as silence. Everywhere there is matter and energy there is vibration which is the basis of sound. It's just a question of is anyone there to hear it and is it at a biologically relevant level. I find people who say they seek silence have never actually been exposed to it. Having spent a lot of time in anechoic rooms, it's unnerving. Even at a neural level, your brain really hates silence. There was a good study a few years back (Pare and Collins I think) showing that if you increase the time between pairs of sounds, the neurons that process the tones start synchronizing more and more during the silent period, and your blood pressure starts increasing. Noise is a stressor but so is real silence. What I think people really want is a volume control for life. I could use one for my cat right about now...

I was born deaf, and got cochlear implants a couple years ago. I'm curious about your thoughts regarding deafness and how I might be less developed than the regular person who has access to sounds.

What are your thoughts on a mind that has not been shaped by sounds? I must admit, i feel sort of inferior after reading many of your comments because sound is everything to you. I don't feel incomplete; just really out of touch.

Or maybe I'm kidding myself; I know exactly what I'm missing now that I have the implant and take solace in the fact that I'm rediscovering what others take for granted.

You are in no way less developed - you just have a deficit in a sense. It required a lot of work and compensation both at behavioral and neural levels for you to cope with the environment, but your mind is every bit as rich and complex as a person with normal hearing.

One thing that's always seemed obvious to me but is hard to come up with an experimental paradigm that will prove it, is that we will create our world from our senses that uses all available channels of information to reach a useful or maximal point. It doesn't matter that others, even of your same species, have different channels available - you'll use the tools you have. Helen Keller is the most obvious example.

And since we don't understand all the ways that senses and how we integrate them build our world, there is a lot more information than the raw data points we do have indicates. For example, when I started working with bats, our understanding of how they build their 3D world using sound was that they get individual "glints" - changes in the echo they get from their call that could identify different structures. The model at the time was something like if you held up a mealworm on a string and a necco wafer on a string, the bat could tell the difference between the two because a mealworm would give a "glint" at each end of the mealworm but only one glint from a Necco wafer (that used to be the favorite candy of bat scientists because a Necco wafer put out the same echo strength as a mealworm - never saw anyone actually eat them but there were rolls all over the lab). The problem with that idea is that it presumed that bats had pointillistic perception of objects. I always presumed that the bats would use these individual glint sensations and create an internal representation of the complex shape, using multiple echoes and glints over time as the bat moved around it or it swayed on the string. I did a series of animations using 3D modeling where I built elements from a bats world (tree, bug that flapped, etc) where I changed the reflectivity of the materials from the way light would reflect to the way sound would reflect, basically by making everything into crystal/glass. Each flat surface could create a glint. Taken as a still, you saw a bunch of sparkles which were hard to figure out. But as soon as I animated it, made the bugs wings flap, the trees leaves move in a virtual wind, made the bat camera view swoop around, it was easy to make out the 3D objects from the individual glints because your brain organizes things into a gestalt - groupings of similar objects. The flapping bug stood out from the tree, the leaves snapped into shape as the "bat" moved through them. Getting the basics of a sensory system is important, but you have to bear in mind that your brain does a lot of things automatically to organize whatever sensory input there is into useful features. Bats don't see a pile of glints - they see a bug in a tree, a flower to pollinate, another bat to chase away. And you learned to reorganize sensory information, visually, haptically etc before your implants and now you've added in a "new sense" that your brain is struggling to integrate into its models of how the world is put together. You'r no less developed than a scientist who listens to the song of pulsars parsecs away using a radio telescope for their "new sense." You just have to learn what it means in a way that's useful to you.

Do you think technology that utilizes our sense will grow in prominence in the next 5-10 years? For example, will we be able to differentiate nerve signals sent from the brain and incorporate specific impulses to trigger specific reactions within a machine?

Brain machine interfacing (brain controlling machines) and neural prostheses (machines controlling/interfacing with brain) are huge areas even now and will become a huge growth industry with the increasing complexity of small electronics. I remember back in 2002 when I started doing vestibular research, my eye tracking rig weighed 5 pounds (head mounted) and was a pain to connect up all the interfaces and then synchronize to a user interface created on MatLab - it made me hate my life. Now I've played with straight software that uses a webcam and a new app someone sent me to evaluate that does it on a smartphone and the results are so much better. I think what will drive it is the DIY bio and coding communities getting involved in citizen science projects. That's one reason I got into 3D printing and have an old school electronics lab in my basement - I can build a LOT of the equipment I use that would otherwise cost my a lot of $$$. the hard part is proper calibration (and the fact that sterilizing my basement would be impossible so I'm not implanting anything homebrewed soon).

I did a report on your work in highschool! Thanks for being so detailed! Quotes helped me pass.

Crap, you mean I'm required reading? My inner fifth grader now hates me.

So what, in your expert opinion, are the know detrimental effects (to humans or anything else living) of existing within a world so absolutely filled with constant, artificial (as in coming from a man-made source) noise, if any? I know that, living near one of the largest UPS hubs in the US, the constant air traffic can get a bit... grating - to put it very mildly - and I'm just curious if there's any empirical evidence to suggest adverse effects from living around all this noise.

Thanks!

Edit: Also, as you may find this interesting - if you haven't seen it already - a video on Lyre birds, narrated by the great David Attenborough (pay special attention to the 1:45 mark onwards).

There are TONS of good studies showing serious physiological and psychological effects of chronic environmental noise. (Here's a sample review - free online - I'm big on open access science - http://www.noiseandhealth.org/article.asp?issn=1463-1741;year=2009;volume=11;issue=44;spage=161;epage=168;aulast=Babisch). Even for levels of 75 dB (which is not considered overly loud), chronic exposure to noise is correlated and in some cases shown to be causative for everything from poor school performance to elevated risk of cardiovascular disease. Part of the problem is that we are so good at relegating elevated noise to the background and if we don't pay attention to it, we think of it as normal and hence don't think of it as a chronic stressor. But it's not just noise - it's what you're used to. When I moved from Brooklyn (near the elevated JMZ subway line) to semi-rural Rhode Island, I went from a normal apartment sound level of 65 dB to about 45 dB and the damn crickets and birds drove me insane for weeks.

And yes I know that video and used it in a class - thanks!

While this might be a redundant question, since you already said you are a scientist, are you an atheist? Or to better phrase it, do you believe that "god" is something that man made up???

I've known very religious scientists but I've never known any fundamentalist scientists. I was raised very reform Jewish (as Lenny Bruce said, so reformed, they're ashamed they're Jewish), but it didn't stick. The idea of an anthropomorphic god always seemed more a comment on our brain evolution than anything tied to reality. We're primates and primate social organization (with few exceptions) is very hierarchical. I think with religion we're just looking for the biggest monkey, but that's just me and I don't give people grief about their beliefs unless it interferes with real life.

What about the idea that it's more a thing that no one can get right? As in, something like a "great unknowable," or summat? Kinda like the Matrix, but far far far deeper.

Definitely. Anything involved in the creation of a universe, whether a Hairy Thunderer or gravity, is going to be a lot more complicated than we can understand at our current level of technology, science and philosophy.

Concert tuning is A-440. But there is a whole subculture of people who are obsessed with tuning A to 432, because it has variously unique properties such as: the hertz of almost all of the other keys become integers, and people conclude that its "more harmonic" ---- my question is, is there such a thing as a most ideally harmonic tuning? and if so? can we blame various regimes in history for forcing 440 into place arbitrarily?

Yeah I know - I've had run ins with the "432 Hz is the heartbeat of the universe" people. Your brain doesn't care if a specific frequency is an integer - it cares about integer based relationships between frequencies, but it's all scaleable. First thing to recognize is that you couldn't even tell the difference between 440 and 432 Hz - it's within what's called your "critical band" - a biological filtering mechanism based largely on spacing of hair cells in the cochlea that limit your frequency resolution. But you could tell that there was something wrong wit5h a harmonic that is only off by a a few Hz. Most sensation and perception is about differences, not absolutes.

Also, you can easily start arguing about if there is a "biological basis" for intonations, but the critical thing is not the absolute frequency but the relationship to other frequencies in a complex sound. In the chapter on music in my book I talk about some of the studies that found what seemed to be a biological basis for western intonation (Plomp & Levelt, 1963 - a classic but not easy to read), but I also talk about a study done using gamelan music (which is usually quite hard to take for western listeners) which showed that you can shift the supposed biologically-based perception of consonance and dissonance with exposure to different intonations.

Historically? Well, when you start having a lot more communication and interaction, your need for standards increases. I think the A440 tuning was only adopted in the 1950s. There's nothing magical about it, it's just what happens when an organization decides it has to define things tso that the Prague Philharmonic doesn't suddenly sound like it's playing ragas when it uses a piano tuned in a London concert hall. (Sort of like what happened to Pluto - it's still a damn planet to me!)

Where did you study neuroscience and receive your Ph.D? (I'm aspiring to study neuroscience in the future, however I don't know where to get started or any college with a good program involving it.)

I studied biopsychology as an undergrad at Hunter College/CUNY in NYC, got my masters in Psych and PhD in neuroscience at Brown. Brown has some wonderful people but I would strongly recommend looking around. NYU, Stanford and University of Maryland have great programs.

Since hearing is such a big player in growth and shaping of the mind - what would the equivalent be for deaf people? Or if there is no equivalent, what do deaf people then lack?

I caught quite a bit of flack because I didn't spend a lot of time talking about deaf people and animals in my book, partially because I wanted to focus on sound and hearing but also because being deaf scares the crap out of me (I went deaf very briefly as a very young child - all I remember is that real silence freaks me out). If anyone wants an excellent overview on deafness, I tell them to read "Shouting Won't Help" by Katherine Bouton (I reviewed the book for the NY Times). She gives an excellent overview of what people go through losing their hearing as an adult both from her personal experience and from her research).

But to answer, deaf people rely much more heavily on vision. Just as blind children or adults blind from birth show faster reactions to sound, deaf people, deaf people tend to show enhanced visual responses under some circumstances (good free paper by Bevelier et al here - http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2885708/). Their minds are just as complex as hearing people but they shift the valence, the importance, of input from vision and touch. It's just another demonstration of the amazing plasticity of the human brain - we can compensate for almost anything given attention, motivation and time.

I loved your book, really very interesting. Spent a while after I read it listening to sounds from space in awe until my flatmates got too annoyed. Thanks for writing it, looking forward to the next one.

Thank you - that means a lot to me. I hope the next one will go faster and easier. I have horror stories about the first 6 months of writing it....

Hi Seth, What are the best ways to get involved in consulting for the Hollywood movie industry? I saw a post in which you recommended Kirby's book, which I just ordered. How did you meet David Goyer and Natalie Chaidez? I'm a stem cell scientist in San Diego. Thanks!

I heard from them independently shortly after Popular Science published an excerpt from my book on acoustic weapons (http://www.popsci.com/technology/article/2012-11/acoustic-weapons-book-excerpt). I heard from Ms. Chaidez independently but Mr. Goyer contacted me through the National Academy of Science Science and Entertainment Exchange in LA. If you're interested in doing some consulting, go to their website and contact them with a basic description of your areas of expertise (http://www.scienceandentertainmentexchange.org/scientists).

What are some of the exciting developments going on in the auditory/psychoacoustic sciences that most people don't know about yet?

The recent work in developing hair cells from stem cells, transplanting them into deaf animals and restoring hearing is just frigging stunning to me. I didn't think we'd see anything like that for a decade or more. Also the increasing quality and complexity of neural prostheses is amazing. Cochlear implants blow my mind, especially the newer generation (but they definitely have to up the finer pitch resolution game - they are still not useful for resolving music in most cases). Some of the work I did on the biological basis of echolocation pointed to some algorithms that could increase the resolution of ultrasound a lot. Miniaturized electronics linked to apps to give us wearable ultrasound imaging devices are a good bet. My favorite area though is something I'm still kicking around trying to get some people at NASA interested - we have to start looking at the psychoacoustics of human exploration of space and start putting better microphones on spacecraft. I'd also love to see a Titan autonomous vehicle use bat-like biosonar for guidance.

My 7 year old son has Auditory Processing Disorder, Sensory Processing Disorder and Mixed Expressive, Receptive Language Disorder. He is working really well in mainstream education and wears an FM hearing system in class. Before his diagnosis his behaviour was very difficult, extrememly rigid and anxious and his social skills fell far behind his peers. He has had a very tough time. Accurate diagnosis, Fast ForWord Program, great therapy and a lovely teacher have really helped, however in moving forward in his treatment what new therapies could you recommend? His Audiologist tells me music therapy could be an option... Is there an hospital or university in the US that leads the research in this field? I am looking to get him re evaluated next year, where do you think I should go? Many thanks!

I work with a group called Advanced Brain Technologies who have their own treatment systems that seem to work well (I did the algorithm development for their sleep stuff), but I would look into the American Music Therapy Association (http://www.musictherapy.org/). They have a wonderful listing of resources and have been very helpful when I have spoken to their people in the past. They would probably be a good group to try and help you find the best center near you (I know from a friend whose child has similar conditions that traveling long distances can be a major chore - see if you can find something near you to reduce the stress).

Thanks for the AMA. It means many things to many people, with apparently little in the way of sensitivity or specificity in its 'diagnosis' - so What is your take on the term central auditory processing disorder?

It's a huge umbrella term and it just means the person seems to have a normal auditory periphery (they hear in the physical/sensation based sense) but have problems recognizing or using sounds. It's not my specialty but from conversations with colleagues there are a lot of problems with the diagnoses. To me it seems like there are a lot of factors that could be playing into it, especially attentional pathways, that seem to be ignored. Just because one modality (hearing) seems to be affected more than others doesn't mean it's a hearing problem. Hearing has a very different relationship with attention than vision, but attention is almost always assessed visually.

Wish I could offer more insight - I just think the term is obscures our ignorance about what could be going on rather than offering much help about the underlying causes, rather the same way everything involving hallucinations used to be schizophrenia.

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Yes it's pretty common actually. There's a form of tinnitus called "pulsatile tinnitus" in which you get an enhanced noise burst tied to your heartbeat. You can also hear it if you tend to have moist earwax rather than dry earwax and a chunk slides around in the ear canal. Moist earwax is the default, with dry earwax being more common in asian populations. Also if you're ever in a truly quiet environment like an anechoic room, you will hear a hiss sound which is the sound of air molecules resonating in your external auditory canal. This will eventually be overhwlemed by the sound of your own heartbeat.

The liquid sound could be anything from a drop of water in your ear or a chunk of moist earwax; but I think you're misinterpreting the location of the sound (it's not going to slide down your shoulder blade) but anything in the ear canal is highly intrusive and perceived as abnormally loud so it can kick in a startle reflex which is supposed to heighten your awareness to the location of a sound. Sounds are supposed to be coming from outside your body, so you may be reflexively and inappropriately positioning it outside the ear canal. If you have this happen often, you should probably see an ENT (ear nose and throat physician). It's possible you have a middle ear infection and what you're hearing is the mucous or other material sliding down your eustachian tube towards you throat.

How has the origin of the hair cell characterized its later evolution? Hearing is a lot like touch, isn't it? The inner ear is a roll of skin covered in gelatinous whiskers immersed in fluid. Sound surrounds the cell and physically perturbs it, and the sensation feels like being enveloped by the material producing the sound. Even sight can feel like extending a finger. Sharp objects and dirtiness are unpleasant to see or hear.

One thing about touch is that there are separate systems for pain, pressure, heat and more, so do sight and touch have separations within them between painful stimuli and other categories, or do these senses trigger pain by imagining what it would feel like to touch what they are seeing or hearing?

Really complex question but you've got some great intrinsic insights into how it all works. Hearing and touch are both mechanosensory senses - they rely on a mechanical deformation of a sensor, whether a hair cell embedded in membranes in the ear or one of the 6 or so types of receptors that make up the "touch" complex (for deep pressure, light pressure, vibration, texture, etc). This means that they are much faster than senses like smell and vision which are second messenger based (requiring several milliseconds even to undergo basic transduction of the stimulation into a nerve signal).

Pain however, is really a separate sensory system. It's composed of free nerve endings throughout the body, mostly in the skin, but also vaguely distributed throughout the body in the enteric nervous system. You are very good at localizing external pain because you have a good sensory map of your somatosensory system; but we're really bad at localizing pain and discomfort internally because the lower density of pain (and other type of) receptors makes everything diffuse.

What makes pain an even more problematic sense is how it interacts with attention. One way to think of pain is as a mechanism for redirecting your attention internally, taking it away from looking around out there and focusing on a potential problem in here. The degree to which pain receptors can force your attentional pathways to disengage from the external world is a serious problem. Think about how easy it was to concentrate on anything the last time you had a toothache. At least that was a clear location for the problem, dealt with by a trip to the dentist. Now imagine pain in a place governed by your enteric nervous system, ill defined, hard to localize and, unfortunately really hard to get to. It might be triggered by a small, relatively harmless gall bladder stone which can mimic all the symptoms of a heart attack, to cancer, which can create creeping pain throughout your whole body, with nothing you can do for either without major medical intervention. Unmitigated attention, drawn to a problem you can’t do anything about, which psychologically cuts down your ability to attend to anything outside the perceived damage to your own body. This is the underlying problem of chronic pain – not so much the injury but how it ravages your cognitive resources. This may be why meditation can have significant impact on pain, chronic and otherwise, because it changes the way your brain pays attention rather than doing anything to the pain signals themselves.

So the tl;dr, hearing and touch are both mechanosensory; other senses can definitely be divided up more (but usually aren't) but pain is a special sensory system that seems to have evolved to grab your attention and focus it inward.

What do you think of Nicholas Carr and all of his talk of how the way we use technology is ruining everything about us?

I'm not a big fan - he has some good basic points - there is a lot of truth to the idea of information overload, but I think he makes huge generalizations without really getting into the meat of what's going on and that access to information is a critical resource. I wrote an article for the NY Times about the problem we have with something as basic to survival as listening (http://www.nytimes.com/2012/11/11/opinion/sunday/why-listening-is-so-much-more-than-hearing.html) but my take is that we need to spend more time training ourselves to cope with new amounts and types of information rather than bemoan the fact that it's stressful. This includes taking the time and making the effort to put down the phone, turn off the computer and just go outside and listen to stuff.

What is the most interesting fact about the brain?

To me, the fact that everything you sense, everything you think about, everything you remember, do or consider, changes your brain physically and functionally, and yet, somehow, whatever the mind is, it persists throughout the chaos.

This is fascinating! I watched "Charles Limb: Building the musical muscle" TED talk a while back and have been curious about the missing link between the auditory system (implant) and brain interface for restoring perfect hearing. I even took a Speech processing course as a graduate student (I'm a EE student specializing in embedded systems). From what I understand, the decoding done by the brain is still a bit of mystery and not feasible in implants yet. Do you see perfect hearing implants in the near future? Thank you for the AMA!

Remember that cochlear implants are still microphone banks that put out temporally-constrained electrical signals that your brain then has to interpret. Implants and hearing aids help with the sensation, but the perception is still wrapped up in the brain. I think the future will lie in better understand of how the brain encodes the raw neural or prosthetic signal and come up with better and more naturalistic codes to pass on to the cortex. One of my professors at Brown came up with the first functional neural prostheses for locked in patients back in the 90s, but they're still trying to get it to work in more than a few people with limited outcome.

There's this perception that with all the science and engineering progress that we should be much further along than we are. But that's ignoring the fact that getting a working proof of concept device is very far from having a "perfect" system. Hearing prostheses have come a very long way from the old amplifier in a seashell hearing aid 100 years ago, but a truly artificial ear whose signals the brain can interpret as a normal auditory periphery is probably still some time away.

Hey Seth, I know I'm way late for this but I just wanted to ask you something. I'm a musician by trade and ever since I really started listening, I've been obsessed with sound. Even though I do stuff meant for audiences, I will still play around with modular synths and enjoy a good sine wave from time to time. Its change in texture, its change in pressure and color just mesmerize me.

I am going to start grad school soon and hopefully, if everything goes well, I'll continue on to my doctorate and hopefully apply my musical and artistic skills to a particular area of psychology. I've looked into how sound can impact the brain, manipulate the nervous system and even cause physical damage to tissue. I really want to look into more abstract concepts such as sound aiding certain mental/personality disorders as well as sound being applied to the military and communication fields. I'm looking forward to reading The Universal Sense! It really delves into what I want to do for the rest of my life.

Any other books I should read in order to have a better grasp on neuroscience? I've been an audiophile all my life and I'm lacking in the science department, but I'm a quick learner. I can't even begin to explain how exciting this AMA is for me and I'm pretty bummed I missed it. Also, if you're in the LA area and need some help around the office, I'll work for free..... seriously. Any tips, or guidance that can help me in my future research would be greatly appreciated. Thanks in advance.

Thanks for the offer - I may end up in LA because it's possible my sound design company NeuroPop may contribute to one of the science fiction TV projects I'm consulting on. I designed an alien echolocation "language" and it may end up getting used...I hope.

Re other books, absolutely read Oliver Sacks "Musicophilia." It's one of the best books out there with a clinical eye to music and the brain/mind. The Emotional Brain by Joseph LeDoux is much more hard neuro but it's an excellent view of emotion in the brain, and since sound and music are such strong emotional triggers it's invaluable. If you want a comparative (non-human) view, I enjoyed Bernie Krause's "The Great Animal Orchestra" which looks at music evolving from animal communication. If you want to read a classic (more old school psychology but still covers important topics in a good way) read Seashore's "Psychology of Music." It goes over some of the classic studies in a very readable way. Good luck!

Have you ever done any kind of study on the connection between sounds and migraines? Also, do you know what the best set of headphones is?

There are strong links between the two, although it's not a causative one. If you’ve ever had a migraine headache, you know that some of the first warning signs are sensory – the appearance of visual “auras” around objects, heightened sensitivity to sound, making the slightest noise a trigger for incredible pain, overall heightened sensitivity to all other senses, feeling like your body is the wrong shape or your tongue is too big to fit in your mouth, exaggerated smells and tastes or even vertigo and the panic and emotional storms that come with it. Migraines are not sensory disorders - they're probably neurovascular in origin. But the appearance of sensory symptoms in a central brain disorder shows the depth of our connection to our sensory world.

Re: headphones, I don't know about the best but I really like my Audio-Technica ATH-M50s.

Sound designer, huh?

If I wanted to build a "sound-box" to compare the loudness of various objects as they strike a metal plate / compare how well walls of different materials block a certain noise, should I aim to make an echo chamber or an anechoic chamber?

Also, who chose the word "anechoic," because I think they secretly enjoy people accidentally saying "anti-echoic."

To get any basic acoustic info, you would definitely go for an anechoic room to drop out the artifacts from the 10s to 100s of thousands of echoes that make up normal room reverb.

an- is a prefix means "not" derived from Greek, so anechoic (first used in the late 1940s) means "not making echoes."

Have you attempted to 3D-print a model of the brain yet?

Yup - there are lots of those out there (check thingiverse - http://www.thingiverse.com/thing:14376 for example). I used to make 3D prints of their own MRI scans as presents. My favorite print though is the 10X normal size human inner ear derived from MRI data (http://www.thingiverse.com/thing:27340).

Just wanted to say thanks for doing this AMA, I've become extremely interested in all things sound after reading through these.

2 questions, 1 statement.

Statement: I know this isn't your alt reddit account that you love so dearly, but I hope you will appreciate that I took the time to upvote the shit out of your whole history.

Question 1: What's the best place to buy your book from in terms of you-actually-making-money? (I want to read it out of interest, but also want to throw money at you for being smart and sharing your knowledge.)

Question 2: What do you think abut the idea of a reddit-sponsored TED talks team? There seem to be a great number of redditors with scientific and sharing minds, I think it would be awesome to crowd-fund a team of 10 or so redditor scientists to go to a TED.

Most important Since you said you frequent AMAs, and I haven't seen it asked... Would you rather fight 100 bat-sized horses, or 1 horse-sized bat?

Thank you - I do appreciate it. I 'm surprised no one with reddit-fu has outed my other account yet.

Q1: There's really no difference although I always tell people go to a brick and mortar, physical book shop in your neighborhood. Need to support bookshops. Amazon doesn't have bathrooms. I know Barnes & Noble carries it - I don't know who else. But if you want to buy it online, I usually send people to Amazon just because they have the best tracking information for authors so I get some idea of how sales are going (http://www.amazon.com/Universal-Sense-Hearing-Shapes-Mind/dp/1608190900/ref=sr_1_1?ie=UTF8&qid=1327890122&sr=8-1). Helps keep my publisher honest (although frankly Bloomsbury's been pretty cool - my editors have been great and had to put up with a lot from a first time popular science writer)

Q2: I think that would be amazing. I always wanted to do a TED talk, but the invitations for the basic 'real" TEDs are few and far between, and as I understand it, all the other ones you pay to enter and I'm not really okay with that idea. But if you try and set something like that up, let me know if I can help.

MOST IMPORTANT: Definitely 100 bat sized horses. First, I love bats and have only run into 2 mean ones in all the time I worked with them. Worst one was Vlad. Big brown bat. Serious asshole. But he was a damn good bat for behavior so we tolerated his constant attempts to shred us. The other was Delilah, a hipposideros constant frequency bat. BIG. Beautiful. Mean as a junkyard bat. But for the most part they are pretty calm, well behaved, interested in eating, flying and napping and once they've been handled for a bit and learn to eat from your hand and then a dish, they are easier to work with than mice.

On the other hand horses. I have been kicked, bitten, thrown and dragged by almost every horse I encountered. Particularly remember Scuba, a horse in NYC's Claremont stables who would get spooked by loud noises and run full force towards the nearest thing he could use to scrape me off. Nothing like a noise-sensitive horse in New York City's central park. I would train the horse sized bat to echolocate and eat the tiny horses (after I figured out how to let him move around - square cube law and all that).

Wow. Really great AMA. I'll try to find your books at the bookstore later.

Alright, here goes my questiom, how does music preferences affect the brain? Are they really limited to "cultural delight" and "enforcing identitiy", or are they worth something more?

Beside th eextensively researched classical music of course.

Thanks again for the amazing AMA !

Music preference is based on a LOT of different things, but much of it comes down to exposure wrapped around the basic biology. The basic biology means you can't resolve frequencies within your critical band, you can't really hear sounds above 20 kHz or below 10 Hz, etc. But exposure helps shape how you use the basic tools laid down genetically. Humans start hearing in the third trimester when the ears connect up to the brain and are exposed to low frequency sounds from inside the mother's body and some loud sounds that are transmitted relatively orthogonally (perpendicular to) to her abdomen. After you're born, there is a huge increase in the type and loudness of sounds (no wonder newborns cry - it got loud! And as you age and develop, those types of sounds and music you are exposed to most will help organize brain pathways and make them more familiar and easier to trigger. So specific music your parents played around you, intonations and styles your culture exposes you to, all of it adds up.

Western classical music, as you pointed out, has been the most extensively researched (which creates problems such as "The Mozart Effect" which is what happens when popular culture and media intersects with science). But that's created a bias - western culture is most enmeshed i nscientific publishing and scientists will work with what they know and don't have to pay royalties to use. Then the next round of experiments want to cite previous work so they'll use the same subset. It's locked out a lot of interesting music that doesn't strictly fit many of the criteria of western music. I talk about how western listeners can change their evaluation of gamelan music (which sounds detuned to many western ears on first exposure) just based on prior exposure in my book, as well as evaluation of emotional content in western and mafa (african) music by naive listeners (http://scienceblogs.com/cognitivedaily/2009/04/08/even-isolated-cultures-underst/).

So tl;dr - music preference is largely based on personal exposure wrapped around your biological limits. But there are cross-cultural commonalities to basic elements of music that are worth looking in to.

What kind of 3d printer(s) do you have? Do you design the prints yourself?

I'm currently using a Makerbot Replicator dual, but I have a Cupcake (still works, just kind of a museum piece) and a Thingomatic (which I use for parts - it was overdesigned and not reliable). I had a Botmill reprap but hated it - poorly manufactured, customer service who lied. Was very glad they went under.

I design most of my own models but have to share the printer with my wife who is a biomimetic and sound artist who also loves the unit and has had some of her museum and gallery pieces built from 3D printed parts (http://chinablueart.com/FireflyProjects.html). Mostly I use data sets to create space terrains like asteroids, lunar and planetary globes etc because I'm working on a project to bring space science to the blind using touchable models. I post most of my stuff (and get a lot of useful models by other people) on thingiverse.com. My username is neurothing is you want to see some of my space and other models (http://www.thingiverse.com/search?q=neurothing&sa=).