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Lecture 5: Brain and Behavior
Visual system:
Everything beings in the retina. The retina is part of the central nervous system.
The retina grows out from the brain. Everything is divided in a simple but
complicated way. The retine is divided right down the middle, so there two halves.
The half that is closes to the nose is called the nasal portion. The outside halves are
called the temporal portions of the retina. What goes on in these two portions are
very different. Each half of the retina forms a specific connection with the brain.
Towards the very bottom, you can see the cortex. We are talking about area 17. At
the very top there are the eyeballs at the back of the eyeball is the retina, and there
are nerve leaving it. If you look to the left. Nerve: pathway outside the central
nervous system. Tract: pathway inside the central nervous system. Even though the
eye is part of the central nervous system, we break the rule and call it the optic
nerve. The point where the nerves from the two eyes come together and crossover
and they continue back and go on up into the brain, this is called an optic chiasm.
When it moves back towards the brain it is called the optic tract.
The tracts for temporal portion go into the cortex on the same side. So the left nerve
of the temporal portion would go on the left side of the brain. However, the nerve of
the nasal portion goes into the cortex on the opposite side of the brain. So for the left
nerve of the nasal portion would go on the right side of the brain. So the information
of the center of your retina, cross to the other side of the brain. The part of the retina
that is seeing (the prof) things on the outside portion, that information is moved to
the same side of the brain.
So something in the right visual field is going to hit the right nasal portion and the
left temporal portion.
Terms; everything that you see is your visual field.
The farther you are out of the PNS, the more simple things are. If you record the
information from the retina, what makes it work and what makes it excited. It gets
excited because a single spot of light hits on a receptor field of a particular neuron.
By the time you get to the area 17, and then neurons can take information that they
have gotten from the retina and put it together and they can work off of that
information. The neurons in the retina respond to a particular line of a particular
orientation but they wont respond to lines of other orientation. By the time you get
to the associational cortex, these neurons response to much more complex
information and they respond to objects such as faces and hands
Therefore the behavior deficit in a patient is directly related to where the damage is
in the brain. The more peripheral /closer to the retina it is the simpler the problem.
If you get damage at the level of the cortex. If you get complete damage at the cortex.
If you have a massive stroke in the posterior cerebral artery, on the right hand side
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