[Image Source] FLASHBACK
There are a lot of awesome things with vision, so I thought I would continue talking about vision today with blindsight. Blindsight is not as this image suggests, some kind of extrasensory power (so why did I choose it you may ask? Let’s go with ‘Because it was awesome and come up for a google image search of blindsight’), but in my opinion, the actual phenomenon of blindsight is even cooler than that.
There are many causes of blindness. Light is received by photoreceptors in the eyes as we’ve discussed and then sent back to the primary visual cortex (in the back of the brain- occipital lobe) where basic processing occurs and then routed around the parietal and temporal cortex (the sides of your brain) for further processing. You can lose vision due to issues with your eyes, damages to the neurons that carry the information from the eyes to visual cortex, or visual cortex. If someone is blind due to a lesion in visual cortex, they have the potential to have blindsight.
Blindsight is when someone who cannot see a ball catches it right out of the air. It’s when a blind person cannot see or know what obstacles are on the floor (like Johnny’s toy car or Jan’s plastic dinosaur), but steps over or around them anyway. Awesome, right? How does it happen? If a blind person is blind because of damage to the visual cortex, they cannot consciously see anything. However, the eyes still send information along that path, which we believe goes to the superior colliculus. The SC then can use that information to keep the person from tripping over an obstacle or from letting that tossed ball hit their face- even though the blind person will honestly tell you they cannot at all see the ball or the obstacle.