miss akay

Visual Neuroscience amazes me!

Tonight, I had one of those lectures, where I was so fascinated by the material, that I had to tell my professor as I left the classroom! We've been studying about the neural pathway from the retina, through the thalamus, to the striate cortex (occiputal lobe) of the brain and most of it is okay, but when you actually get to the striate cortex.... omigawd! It seriously blows my mind. Scientists Hubel and Wiesel conducted experiments to determine whether cells have a preference for the direction of light that stimulates each particular cell. As it turns out, many of them do! One cell likes light at a 45 degree angle, another likes it at 60 degrees. The cells that have the same preferential orientation, stack on top of one another through the whole cortex thickness. (this will probably start getting boring for most normal people) Some cells are excited by darkness and others by light. Then there are cells that have a perference to a particular eye, meaning the cell is binocular, but it is driven by one eye stronger than the other. If you inject a marker amino acid into the left eye and then inspect the striate cortex, you will see a zebra/fingerprint pattern all over, indicating which eye is driven onto what sections of the cortex. Again, you get these stripes that run through the whole cortex, like from the the ceiling of a wall down to the carpet.... all driven by the same eye! But still binocular (except at Layer 4C) meaning the cell gets signal from both eyes! The experiments conducted to give evidence to these theories are really cool, too. Dr. McLean showed a video of the scientists testing for action potentials as they dragged a stripe of light across the screen, to determine someone's receptive field and what type of response triggered it. When they map it all out and color code the areas that prefer a certain orientation, driven by a given eye, etc. you end up with a little cube of the cortex devoted to convey all that information. And it is all swirled together. Each functional module follows its own system and pattern, but when you line up the various functions (orientation, color, position, motion, ect.) it is mind blowingly complicated. It is art. Seriously! That's the only way to sum it up. wow!

posted by miss akay @ 9:11 PM