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Jen Benson's picture

environmental niches; separate nerve tracts

I think it's really value to remember that sensory systems reflect partially the environments that organisms have to live in and how they have evolved to most efficiently survive there. Receptor organs themselves can vary between species and reflect different survival strategies. For example, honeybees benefit from having two different kinds of ees, while panther chameleons can move their eyes independently from one another, the Philippine tarsier can very well in the dark and forage for food, and the American bald eagle's eyes are extremely sharp, all reflecting environment-specific needs of each species. (Breedlove, Rosenzweig, and Watson, 2007, Biological Psychology). Each species also varies in the range of their responsiveness to different kinds of sensory input, for example different frequencies of sound and light that are more accessible to some species than to others. I think it would be quite interesting to examine how recently the brain has evolved to its current structure in terms of sensory perception, and the past environments that helped shape those systems in early humans.

In a separate vein, I was thinking about our discussion about how each sensory modality sends action potentials along different nerve lines, which is how we are able to distinguish different kinds of sensory input. That's why when we press on our eyeball, we see a blob with your eye, since the pressure causes action potentials coming from the eye that are thus labeled by the brain as always carrying visual information (Breedlove et al., 2007). I have definitely felt things in my eyes before though so this explanation somewhat confuses me. Temperature perception is also supposed to be a kind of perception separate from touch. Does that mean that a portion of a surface of the body can have receptor areas connected to more than one nerve tract (and thus be able to produce more than one kind of sensory input to the brain)? Any clarification of this would be greatly appreciated.

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