The Tell-Tale Brain

In Chapter 2, Ramachandran explores how the brain processes visual information and what makes human visual processing unique compared with other primates. First, the brain sees thousands of different shades via three types of cones in our eyes that sense red, blue, and green light. Humans are one of the few mammals with three cones. Most other mammals only have two.

Second, while many organisms have eyes and vision, perception is unique to humans. The brain builds a model of what a person is seeing based on information streaming into the brain from the eye. However, this model is not literally based on what our eyes see, since there is a blind spot where the retina and optic nerve connect. Humans do not perceive this blind spot, because the brain takes shortcuts filling in the missing information. Humans are not seeing the original image but a recreated image that may or may not be correct. Canonical nerves located in the frontal lobe help the brain process visual information. They fire at both a specific action (e.g., grabbing an apple) and at the site of perceived action (e.g., the site of an apple which leads to the abstract notion of graspability).