Neuroanatomy Notes 07/20/99

NEUROANATOMY NOTES 07/20/99

Profesor: Dr. Martinez Sandoval

Motor and Sensory Cortexes there is a firing of cells when there is a single flexion movment. There are motor neurons in the primary motor cortex. there are sensory neurons in the sensory cortex. there are motor neurons intermingling with the sensory neurons in the sensory cortex. If you do a complex movement, you can see participation not only of the motor neurons in the motor and sensory cortexes, but you will also see the firing of motor cells in MII, the upper part of the cerebral cortex. Here you have the mingling of cells in area 4, 6, and areas 3, 1, 2. When you ask the person not to perform any movement,but just think in the movement, then the firing lies only in the motor neurons in the area MII. That's why yesterday we mentioned that area MII is the most important for the origin and planning of the complex movements you will perform. That's why we said before that the motor neurons in area MII fire 800 ms before area 4.

Large cube mapping. Planning complex movements and elaboration of thoughts are found in the prefrontal cortex. The way I will react after feeling, listening, or watching something, what is the type of response I will do? This refers to the planning of the complex movements (MII). MII tells you which muscles to move. Brocas area are 44, 45.

Somatic Sensory deals with pain, temp, light touch, propioception. Propioception tells you the position of your feet, lower limbs, or any part of the body. Allows you to detect the degree of stretching of the muscle. It means the capability to detect the shape, volume, of objects by means of pressure and touch without the use of sight. Area 5, 7, and part of 40(supramarginal gyrus) deals with the spatial coordinates of your body and surrounding. You can explain the position of the body when you are doing some performance. For example, a pitcher in baseball, on the mound, just as he raises the lower limb, he needs to keep equilibrium, and his area is detecting the position of his body as it moves. He is using the sight because he is looking around.

Wernicke's Area deals with Language, Comprehension, intelligence. Located in areas 22, 39, 40. This is where you comprehend what you want to say before sending it to other regions of the brain for execution. From Wernicke's area you send it to word formation at Broca's Area.

Area 37 is involved with naming of objects. Deals with visual processing of the words. That is how you read "Mama" and identify the words, visually. So, the processing of the visual processing belongs to area 39, in the angular gyrus. This is supplied by the terminal branch of the middle cerebral artery. Normally, the middle cerebral artery runs deep to the lateral fissure. You observe lateral branches for areas 11, 12 (frontal polar artery), precentral artery for motor areas, suborbital 44, 45, and postcentral artery, and posterior parietal branch for areas 7, 5, and the terminal branch, angular artery supplies wernicke's area. These are big arteries, and when you try to understand these ascending branches from the middle cerebral artery, we have the anterior temporal branches, and posterior temporal branches. And as you conclude that, try to think that when you have a large vascular problem that affects the main trunk of the middle cerebral artery at the level at the lower surface of the brain, or if its a lesion only at the level of the precentral artery, you will have different regions of the brain affected. Therefore, its important to know the middle cerebral artery because its the most important artery of the brain.

Look at the horizontal section of the brain (he shows slide of superior view of horizontal section of brain). The middle cerebral artery will supply structures that lie deep to the lateral fissure in the temporal lobe, and it sneaks into the insular cortex of the brain. Then, deep to the isular cortex, you can see the large basal nuclei. The artery penetrates with its lenticular branches (to the caudate and putamen). You can identify the caudate nucleus. These arteries are called the lateral lenticulo-striated arteries.

Looking at the same slide, he outlines the gross anatomy of the thalamus. Can identify anterio, medial, and lateral group. We're going to have the lecture on the thalamus later on, these are only generalities. The thalamus, in the postero-latero-inferio regions, according to your academic terminology, there are two thalamus. I can take only one thalamus. I can divide the thalamus into anterior and posterior half. Or I can divide the thalamus into lateral and medial half. So, from the postero-infero-lateral part, see nucleus known as the lateral geniculate nucleus or body. This is the last relay nucleus of the visual pathways. Neurons in the lateral geniculate nucleus, will project. He draws axons leaving the thalamus towards the occipital region of brain. The axons are drawn anteriorly, then hook back towards the posterior part of the brain. There are optic radiations which finish above and below the calcarine fissure (areas 17, 18, 19). Now, look, the positions of the middle cerebral artery, and it supplies the optic radiations. This part is easily forgotten during examinations. So, affections of the middle cerebral artery lesions will affect the areas on the superficial part of the brain, but sometimes we forget that the middle cerebral artery's lateral perforating branches will supply the internal capsule, thalamus, and most importantly, the visual pathway optic radiations. contralateral harmonious heminopsia results from lesions in this artery.

He puts up slides from Fick's book that shows lesions of the brain and its effects. Contralateral hemiplasia will result if there is a lesion in the postcentral gyrus. What cranial nerve controls this? Remember that the most important is the facial nerve. You may have right hemiplasia because of areas 4, 6, MII being affected. However, you will also have an affected nerve, which is usually the facial nerve, because the left hemisphere of brain controls the right lower face muscles. Secondly, cranial nerves also affected are Hypoglossal nerve and abducens nerve will lead to a slight deviation of the tongue and medial strabismus. Because the abducens produces the lateral movement of the eye. When you have weakness in the eye, the eye tends to move medially. The hypoglossal nerve supplies all 18 muscles of the tongue. Some specials muscles are important for primary movements of tongue. Protrusion of tongue produced by the genioglossus m. This m. pushes tongue medially and forwrad. The contralateral m. pushes medially and forward, ultimately causing protrusion of the tongue. Have contralateral deviation of the tongue from the sight of the lesion.

There are some problems in the soft palatte with the jugular m. supplied by the vagus. The jugular m. is supplied by the contralateral cerebral hemisphere. When there is problem on right side of brain, see jugular m. pushed off to the left side. So, hemiplasia and contralateral facial paralysis occurs from lesions in the brain due to problems with the middle cerebral artery.

He returns to the slide from Fick's book. Lesions in area 8 will cause the head and eyes to turn to the left. However, lets suppose that you are here, again, this is the central fissure. He outlines the central fissure. He outlines the superiorfrontal gyrus, and the precentral gyrus, and then circles area 8. The patient sees towards the lesions. The patient "sees" his lesion. When you have a lesion, you have a dipsilateral deviation of eyes towards same side. However, in the precentral gyrus, he shows us where the brain controls the larynx, pharynx, lips, head, eyes, etc. The region of the precentral gyrus that controls the eyes and heads are located near the area 8.

Phineas Gage Syndrome or Frontal lobe syndrome. Lesions in regions covered by areas 9-12 lead to problems in personality, and inappropriate social behavior. You can suffer an epileptic crisis there which may lead to these problems. This frontal lobe syndrome also deals with loss of initiative, sphincteric incontinence, release of sucking and grasping reflexes, gait apraxia.

Arcuate Fasciculus can be severed and leads to conduction aphasia because there is no longer connection between brocas and wernicke's areas.

Hemihypesthesia and asterognosis means you can't detect the symbols applied to your skin when you are not looking. You can no longer recognize the shape and volume of the objects.

Lesions in the somatosensory region leads to astatognosis, which means you can't tell the position of the body. You also have right astereognosis and sensory neglect. Sensory neglect means the patient negates the fact that he or she is affected by diesease. This is more sensory neglect from lesions in the right side of the brain than from the left side. The patient urges to his family that he wants to go out of the hospital. He believes he is correct, because he cannot accept that he is affected by the paralysis of the body.

Lesions in areas 40, 39, 22 (Wernicke's Area) leads to Gershman's Syndrome. This syndrome has characteristics of finger agnosia, dysgrapfia (can't write), dyscalculia, allexya -you are unable to read. You're capability of understanding what you read is affected. Dyslexia also affected, and also right/left confusion. Right hemianopia is also caused by lesions here.

Lesions in the hippocampus affects your ability to retain memory. That is the second structure that affects intelligence, along with Wernicke's area. The test takes questions directly from these figures of the brain and the lesions that affect the patient. You need to perfecctly understand this section.

If you look on the right side of the brain, Gershman's syndrome is known as the syndrome of the nondominant inferior parietal lobule. It is not Gershman's syndrome.

What is astatognosis and anosognosia...turn these in by tomorrow at 12:00 for extra credit. .2, .2, that's .4.

Don't miss the figure in Ficke's BRS book on page 355. Please understand correctly the cerebral cortex, and you will answer correctly 10-12 questions.