Blindsight - Describing Blindsight

Describing Blindsight

Simply described, the brain contains several mechanisms involved in vision. Consider two systems in the brain which evolved at different times. The first that evolved is more primitive and resembles the visual system of animals such as fish and frogs. The second to evolve is more complex and is possessed by mammals. The second system seems to be the one that is responsible for our ability to perceive the world around us and the first system is devoted mainly to controlling eye movements and orienting our attention to sudden movements in our periphery. Patients with blindsight have damage to the second, “mammalian” visual system (the visual cortex of the brain and some of the nerve fibers that bring information to it from the eyes). (Carlson, 2010) This phenomenon shows that how, after the more complex visual system is damaged, people can use the primitive visual system of their brains to guide hand movements towards an object even though they can’t see what they are reaching for. Hence, visual information can control behavior without producing a conscious sensation.

Blindsight may be thought of as a converse of the form of anosognosia known as Anton–Babinski syndrome, in which there is full cortical blindness along with the confabulation of visual experience. Blindsight patients show awareness of single visual features, such as edges and motion, but cannot gain a holistic visual percept. This suggests that perceptual awareness is modular as well as the process of perceptual integration that unifies all information into a whole percept. Therefore, object identification and object recognition are thought to be separate process and occur in different areas of the brain, working independently from one another. The modular theory of object perception and integration would account for the “hidden perception” experienced in blindsight patients. Research has shown that visual stimuli with the single visual features of sharp borders, sharp onset/offset times, motion, and low spacial frequency contribute to, but are not strictly necessary for, an object’s salience in blindsight.