October 17 2011
Sensory motor systems:
Frontal lobe primary motor function, in the division of the frontal lobe which is
primary motor. Precentral is motor, postcentral is sensory.
What happens when those areas get damaged? What happens when someone gets
a stroke there. Real world problems. Decoding and rencoding language is also
Talk about visual system, the little homunculus, motor system adamge. Frontal
lobe. Parkinson’s disease.
Sensory and motor systems today.
Anatomical organization and functional organization. What kind of things could be
wrong with this person?
Eyes: retinas are right down the middle. Anatomically divided. Visual field. Is what
you see, what the person can see out there. Technically divided into right half field,
and left half field. Real world we shorten it, the right visual field and left visual field.
Your nervous system is divided in such a way so that your fields are divided into
halfs because your retinas are divided into two halves. Retina part closest to nose is
the nasal portion. Part of the retina that is closest to the nose. Other half of the
retina that is cloest to your head or temple, is the temporal portion.
The nerves come together from the eyes to a point to a single nerve, single point.
Separate nerves leaving the eyes are optic nerves. Optic chaism is where they
meet. Then they separate again, this point is called the optic tract. Nerve is
outside, tract is inside. Closest to eye is nerve, closest to brain is tract. The nasal
portion crosses, and the temporal portions stay on the same side. So the temporal
portions go to their respective cortexes, but the nasal portions will cross.
Pupils are very small, light can get into it, but the openings are very small. If you
have something on the left hand side and it gets through the hole. If you take your
hand and hold it off to the right, your nose will block partially. Right hand = nasal
portion of the right, temporal portion of the left. And vice versa. Something in your
right visual field, it’s gonna hit the nasal portion of your right eye, on the temporal
portion of your left eye. Will hit the left hand portion of each eye. Left field goes to
right cortex, left field goes to right cortex. Because the nsal portions will cross. Not retina, but visual field!!!
1. eyes can see more on the right than left, not perfect circles however. Can’t see
much like on the right, can see much further on the right.
2. destroy right nerves, cannot see anything there. Normal vision is completely
3. severing the optic chaism. Only the nasal portions, the tracts that cross. The
nasal portion of each retina. Bitemporal hemianopia. Right eye will not be able to
see something in the far right the left side cannot see out the far left. Blind in the
nasal portions of each eye, so the far left of the left, far right of the right.
4. temporal portion of the right eye. The left eye should be bperfect normal. The
temporal portion of the right eye sees from the left. So that section will be
damaged. Blind on left portion of right eye. Need to use diagrams
5.cut the right optic tract, the person will lose the temporal portion of the right eye,
lose the nasal portion of the left eye. Left eye cannot see from the left, right eye
cannot see from the left either as the temporal portion of the right eye has been
severed. Remember that the temporal sees from the opposite direcition
6. cuttingthe cortex and
7. macular staring, can see from a little dot. If you destroy something earlier on, you
can’t see anything, destroying it later you can still see. Macular sparing. Like
number 5, you won`t be able to see out of the left sides of your eyes because the
nasal section of the left eye has been destroyed, as has the temporal portion of the right eye. Corpus collusm maybe?
So you can tell where the damage is by mapping. Tell where a tumor is through
waving things in patients eyes.
First part anatomy how the system is built, second part function.
What is the function of the nervous system at each of these levels?
The more central the neuron (cortex vs retina, associational cortex vs primary
cortex), the more advanced the area of the brian, the more complex the image is
that excites it. The more complex the images that excite it. In the retina, a neuron
responds to a spot of light falling on its receptive field. Light falls on the field or it
doesn’t. dark or light. Area 17, primary receptive area for the occipital lobe, there,
the neuron can decipher lines of light oriented in a specific direction, not simple but
also not complicated. In the associational cortex, they integrate information form
neurons and but information together. Neurons there are able to build up
information that can respond to faces or hands. Or specific faces or specifc hands. Much higher order. Like a computer, build upon information from the source to the
next level. Even further the neruons respond to specific faces and specific hands.
Build on information from the perivous source and takes it to the next level.
You can tell a lesion based on what they cannot see. But not able to recognize
things is a different story.
If you get complete damage to the right occipital cortex, a major stroke into the
posterior cerebral artery of the right cerebral occipital cortex, you will get complete
blindness in the left hand side, left hand visual field except for that tiny little spot in
the middle, macular sparing. If you get incomplete damage in the right occiptital
cortex, then you will get partial blindness from the opposite visual field. Small
amount of damage, then a tiny area of blindness in the opposite visual field. Smaller
and smaller, scotoma. Small area of of blindness in the visual field where the nerves
leave the retina where rods and cone don’t exist. Refers to the behaviour. We each
have a small soctoma, that is natural. We don’t notice that we have a scotoma.
20, 21, 17, 18, 19 in more complex areas, you will miss faces on the right hand side
of the brain. Have problems with faces, complex material. Faces on right, verbal
material on the left hand side of the brain. Language is on the left side of the brain,
right next to the temporal lobe. Right is spatial kind of information that is lost. When
you have this kind of damage, you have perceptual problems. Faces and patterns
are lost. Particullary with faces, there are of syndromes associated with this. More
on the right side, verbally related on the left hand side of the brain. Language is on
the left hand side of the brain. When you have thse kind of damages, these are
known as syndromes associated with specific ares. We understand these syndromes
more through their behaviour than the damage to their brain.
What they can or cannot do. Syndromes of behaviours.
Visual agnoisa: a means you can’t do it. Don’t know, don’t understand. Inability to
recognize objects for what they are. Typically damage from left occipital lobe. Pick
up something and show them it and ask them what it is. Need to know what’s
wrong with the brain and need to tell what the patient can and cannot do, although
a MRI can tell you maybe what they can and cannot do. They c annot figure what it
is or used for. Typically from the left occipital lobe.
Another very classic syndrome is prosophenosia , person cannot recognize faces.
Cannot distinguish faces. There are very subtle differences in faces, especially in
familes etc. Whenever there is damage to higher order structures, not being able to
recognize faces happens, and is extremely debilitating. Very important to recognize
faces. They also may not be able to recognize other complex objects. Bilateral
damage to 18 and 19. may not distingusih a pineapple and pappaya etc. Color agnosia: a problem with colors, the colors seem less intense to people after
damage. In extreme cases they may lose color vision completely. Usually a loss of
color. Typically from bilateral damage to the occipital temporal area.
Like pixelated videos. You can see it, but you don’t have enoguh processing power
to say who it is, only that it is.
Everything you see in the right visual field hits the left half. Everytihng from the left
half hits the right hand side.
Somatasensory information comes in to the postcentral gyrus. Parietal lobe, just
past the central sulcuss, the sensory humunuclus. What happens when you get
damage in this area of the brain? In the parietal cortex in the somatasensory
systen. You get altered sensory thresholds. For example: we can test this at the
best side, touch the person soft or touch the person hard. Can also see how much
they can distinguish to whether something is one point or two points. Normally
people can sense this very well on hands, but with damage to their somatsenosry
thresholsd, they may not be able to tell. People with damage cannot distinguish
thresholds, cannot tell where they are being touched. Altered sensory thresholds.
Cannot distinguish as precisely as people with normal cortexes.
The rough stuff is gett