neuroscientist here. so I already noticed you said we're not yet aware of the exact mechanisms at play, but has anything at least been ruled out? Are there at least any clues pointing at a particular level of explanation?
For example, the much-mentioned toxoplasmosis gondii, i believe, influences behavior in a rather nonspecific way -- IIRC, the antibodies that its presence engenders alter dopamine-related neurotransmission in the nervous system in general. The specific effects on behavior, then, are due to the intrinsic functional specializations of DA in the normal brain, as opposed to a specific targeting of, say, 'risk' or 'fear' circuitry by the parasite itself. In other words, the parasite 'alters behavior' not by targeting the neural bases of these specific behaviors per se, but by producing subtle changes in some large-scale neurotransmitter system which itself happens to have a particular intrinsic functional specialization. The end result, behaviorally speaking, is of course the same -- but the level of explanation, and the degree of mechanistic sophistication is very different from what most people would imagine when they think of something as 'controlling' behavior.
From what little I know of the cordyceps fungus, it causes ants (?) to climb up stalks of plants and stay there until they die / sprout a fungal bloom, no? So, thinking in terms of broad behavior with simple mechanisms, you might expect to find that this behavior could be effectively 'caused' by messing around with some neural system related to a) phototaxis/photosensitivity (trick the ant into climbing up somewhere high by messing with its perception of / desire for light) and b) general activity level (i.e. lock a neural system that cycles through rest/activity cycles into a permanent 'rest' state). If a parasite could find a way to do both of those simultaneously then you'd have an effective recipe for the observed behavior, albeit at a lower level of specificity/sophistication than whole-brain 'hijacking'.
And in fact, there is actually a precedent for linking these two domains of behavior, because we know that -- in vertebrates at least -- brain-wide arousal mechanisms are coupled to the day/night cycle by particular photoreceptors in the eye that specifically detect wavelengths of light unique to sunshine. Now I'm not a comparative evolutionary neuroscientist, so i don't know how neurobiologically plausible this functional connection would be in the case of ant biology -- but this scenario would at least motivate the search for parasitic mechanisms of behavioral control that are normally related to those behaviors in uninfected ants.
Mind you, this is all me just spit-balling here, but despite not knowing much about it specifically, this topic has interested me for some time. So what do you think? do you think these parasitic alterations of behavior are due to sophisticated mechanisms that directly target behavior-relevant aspects of the brain, or do you think there are simpler ways of explaining this behavior?
terist8 karma
neuroscientist here. so I already noticed you said we're not yet aware of the exact mechanisms at play, but has anything at least been ruled out? Are there at least any clues pointing at a particular level of explanation?
For example, the much-mentioned toxoplasmosis gondii, i believe, influences behavior in a rather nonspecific way -- IIRC, the antibodies that its presence engenders alter dopamine-related neurotransmission in the nervous system in general. The specific effects on behavior, then, are due to the intrinsic functional specializations of DA in the normal brain, as opposed to a specific targeting of, say, 'risk' or 'fear' circuitry by the parasite itself. In other words, the parasite 'alters behavior' not by targeting the neural bases of these specific behaviors per se, but by producing subtle changes in some large-scale neurotransmitter system which itself happens to have a particular intrinsic functional specialization. The end result, behaviorally speaking, is of course the same -- but the level of explanation, and the degree of mechanistic sophistication is very different from what most people would imagine when they think of something as 'controlling' behavior.
From what little I know of the cordyceps fungus, it causes ants (?) to climb up stalks of plants and stay there until they die / sprout a fungal bloom, no? So, thinking in terms of broad behavior with simple mechanisms, you might expect to find that this behavior could be effectively 'caused' by messing around with some neural system related to a) phototaxis/photosensitivity (trick the ant into climbing up somewhere high by messing with its perception of / desire for light) and b) general activity level (i.e. lock a neural system that cycles through rest/activity cycles into a permanent 'rest' state). If a parasite could find a way to do both of those simultaneously then you'd have an effective recipe for the observed behavior, albeit at a lower level of specificity/sophistication than whole-brain 'hijacking'.
And in fact, there is actually a precedent for linking these two domains of behavior, because we know that -- in vertebrates at least -- brain-wide arousal mechanisms are coupled to the day/night cycle by particular photoreceptors in the eye that specifically detect wavelengths of light unique to sunshine. Now I'm not a comparative evolutionary neuroscientist, so i don't know how neurobiologically plausible this functional connection would be in the case of ant biology -- but this scenario would at least motivate the search for parasitic mechanisms of behavioral control that are normally related to those behaviors in uninfected ants.
Mind you, this is all me just spit-balling here, but despite not knowing much about it specifically, this topic has interested me for some time. So what do you think? do you think these parasitic alterations of behavior are due to sophisticated mechanisms that directly target behavior-relevant aspects of the brain, or do you think there are simpler ways of explaining this behavior?
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