Primative processing found to persist in primate perception
You’re not aware of it, but your vision is really a collection of inputs and reactions, parsed and assembled in multiple ways by your brain. This isn’t just the mechanical issue of how saccades have your eyes darting around to gather detail on your limited area of focus. Nor is it the fact that your eyes gather color and value information separately in rod and cone cells. Once the light receptors in your eye have sent information down your optic nerve, it’s actually shuffled off to more than one area in the brain to be processed. Some of this processing, such as the complex assembly of three-dimensional space from your binocular vision, has been known for some time. However, researchers have just uncovered that we seem to also have some much more primitive visual processing in our heads, once thought to have been abandoned by our primate ancestors.
The more primitive vision in question can be understood through the life of a rat. With eyes on the side of its head, a rat’s primary visual concern is looking out for movement from the many potential predators in the rat’s world. Since rats depend greatly on smell and hearing for navigation and finding food, their eyes have specialized as alarm triggers. To initiate a quick, evasive response to possible danger, optical information from both eyes passes first through the lateral geniculate nucleus, or LCN, before heading to areas like the amygdala, where a fight or flight reaction can be triggered. That way minimal time will be spent deciphering visual information before the rat begins to move out of danger.
Rat responses and more
Since primates like humans have strongly binocular vision, our brain has allocated many more resources to parsing and assembling complicated visual information. Two slightly different images, one from each eye, go to the visual cortex at the front of the brain, where it’s turned into an useful representation of our environment. The ‘raw’ data from our eyes also passed through our LCN, but it was thought to be degraded, only using information from a single eye at a time. However, recent studies in marmoset monkey brains have found that the double-eyed connection to the LCN has actually lived on, and that gaining binocular vision didn’t mean we traded in our more primitive visual perception after all. There’s a chance that the whole is even greater than the sum of its parts, and that the combination of cognition from the LCN/amygdala loop and our visual cortex helps enable our impressive visual abilities.
Source: 'Rat vision' may give humans best sight of all, Phys.org
