the blind can see!

no, i'm not jesus, nor did i discover a new way to heal the blind. they actually can see. let me explain.

the world around us enters the eye as light, falls on the retina then travels in the optic nerve, the optic chiasm (where it gets all switched up) and then the optic tract to the Lateral Geniculate. from here, the visual information is sent through the optic radiation (inferior visual field via the geniculocalcarine tract and the superior visual field via Meyer's loop) to the occipital lobe of the brain.

if someone has an infarct of the posterior cerebral artery affecting the occipital lobe (the part of our brain that processes visual information) then they have cortical blindness. they can't see anything.

however, if you throw a ball at their head, they will duck, or catch it! trust me, i tried it. how?

remember the lateral geniculate i mentioned? well, not only does it send off the optic radiation to the occipital lobe, but it also sends fibers through the brachium of the superior colliculus to the superior colliculus (SC). from the SC originates the tectospinal tract. this is the tract (or group of nerves) that allows us to respond to a stimuli such as a ball thrown at our head.

in the blind person, they have a lesion that occurs after this branch to the superior colliculus. thus, they duck the ball, or worse, catch it and throw it back! another way to test this phenomenon is to hold a pen in front of the blind person. 9 times out of 10 they will be able to tell you if it is pointing up or down.

so, im not advicating that you throw things at blind people, but i thought i would share this very cool bit of info with you. hope you enjoyed!