Cerebral Cortex Flashcards
What divides the frontal lobe from the parietal lobe?
Central sulcus
What is Broca’s area?
it is located in the left frontal lobe in most people. it controls the muscles in the mouth involved in speech.
What is contralateral neglect?
a unilateral lesion in the parietal lobe will result in a syndrome where patients fail to pay attention to the contralateral side. ex: not draw the other side of a clock
What is the result of lesion in the primary visual cortex?
Visual agnosia-the inability to recognize objects one sees or alexia without agraphia which is the inability to read while retaining the ability to write
What does the primary visual cortex receive inputs from the retina via?
The lateral geniculate nucleus
What does the Primary auditory cortex receive input from the cochlea via?
The medial geniculate nucleus
What would a lesion to CN VIII lead to?
Lesions priot to decussation result in unilateral hearing loss. Lesions after the decussation result in bilateral hearing loss
What would a lesion in the hippocampus lead to?
Anterograde memory loss (inability to form new memories)
What is a common form of seizure arising from the hippocampus?
temporal lobe epilepsy
What is the result of lesion to the amygdala?
ablation of fear response, Kluver-Bucy syndrome
What is wernicke’s area?
it is responsible for the comprehension of speech (both verbal and written). THe patient can produce language sounds but the speech has no meaning. The patient also has no awareness of their difficulty.
Describe the molecular layer (I)
most superficial layer, contnis axons traversing the cortex and glial cell bodies
Describe the external granule layer (II)
very densely populated with neurons, contains small granular and pyramidal cells
Describe the external pyramidal layer (III)
contains pyramidal cells arranged in row formations
Describe the internal granule layer (IV)
thin layers densely populated with neurons
Describe the internal pyramidal layer (V)
contains large pyramidal cells
Descirbe the polymorphic layer (VI)
contains large fusiform-shaped pyramidal cells
What is an agranular cortex?
dominated y large pyramidal cells
What is a granular cortex?
dominated by small cells
What are association fibers?
neurons which connect neurons ni the same hemisphere
What input arrives into layer IV?
from thalamic sensory and relay nuclei
What input arrives into layers II/III
intracortical input
What input terminates in layer VI?
input from intrathalamic nuclei
Where do layer III neurons mainly project to?
other cortical areas
Where do layer V neurons project to?
mainly striatum, brainstem, spinal cord
Where does layer VI project to?
the thalamus
What is the anterior commissure?
It connects the temporal lobes
What is the internal capsule?
It brings the output of the cortex to subcortical sites
What is the superior longitudinal fasciculus (arcuate fasciculus)?
connects frontal with posterior lobe
What is the inferior longtudinal fasciculus?
conects occipital and temporal lobe
what is the superior occipitofrontal fasciculus?
connects frontal with superior parietal and occipital
what is the inferior occipiofrontal fasciculus?
connects frontal with inferior parietal and occipital
what is the subcallosal fasciculus?
it connects cortex to caudate
what is the uncinate fasciculus?
it connects orbital cortex and anterior temporal cortex
what is the cingulum
it forms a nearly complete circle from cingulated to para hippocampus gyrus
what is the extreme capsule
it connects the superior temporal gyrus, insula, orbital and prefrontal cortex
What happens if the somatosensory cortex is lesioned
With eyes closed, the patient can’t tell the direction of passive movement of the great toe or fingers, whether he or she is being touched by one or two points close together, identity of the numbers written on the palm (agraphesthesia), localize the exact area where they are being touched on the affected limb, identity objects placed in hands (astereognosis)
Where do auditory fibers become bilateral?
immediately upon entering brain stem at the pons
What is “pure word deafness”?
if a lesion disrupts auditory cortex pathways to the left language comprehension center, the patient can’t comprehend spoken language. Sounds like everyone is speaking nonsense
What is the result of right side auditory association cortex damage?
difficulty appreciating environmental sounds and music, amusia
What is homonymous hemianopia?
The pattern of visual loss affecting half of the isual field of each eye.
What is a-Anton’s syndrome?
unawareness and denial of cortical blindness
What is Balint syndrome?
only a small part of the visual field (usually central) comes into attention so patient only sees a fragment of the complex scene. There is difficulty in reaching out to the object seen.
What is a clinical finding of a seizure arising from the olfactory cortex?
an aura of unpleasant smell. like burning rubber
What is the most prominent cortical efferent system?
The pyramidal (corticospinal, upper motor neuron) pathway which arises from teh rolandic gyrus just in front of the central sulcus. Stimulating this region results in complex movements
What area does the anteior cerebral artery supply?
The leg
What area does the middle cerebral artery supply?
The face and upper extremity cortical areas.
What is Gerstmann’s syndrome?
lesion of the left inferior parietal lobe
- agraphia-inability to write
- acalculia - inability to do simple arithmetic
- finger agnosia -difficulty in naming fingers
- right-left disorientation - in self or others
What is alexia?
a reading disorder. lesions in suprarmarginal gyrus which is important in converting visual into auditory/verbal info
a dominant parietal lobe symptom
What is apraxia?
high order motor difficulty. part of dominant parietal lobe syndrome
What is non-dominant parietal lobe syndromes?
lesions in the non-dominant parietal lobe will result in severe difficulty in handling spatial problems. there may be unilateral left-sided extinction of visual, auditory and tactile double simultaneous stimuli. The patient will report not feeling, seeing or hearing stimulation from left side if stimulus is done simultaneously but if each side is stimulated separately there will be no deficit. When there is also hemiplegia, the patient will deny the paralysis.
What is conduction aphasia?
The arcuate fasciculus runs from Werencke’s area to Broca’s area and when there is a lesion there, the patient can speak fluently and understand language but cannot repeat phrases, particularly those made up of small grammatical connectives (no ifs ands or buts). The performation gets worse upon repeating.
What is nominal aphasia?
word finding aphasia. if a lesion is limitied to the association cortex of wernike’s area.
What is global aphasia?
This is the most common. It results from simultaneous destructino of Boca’s area, Wernicke’s area and the arcuate fasciculus. This happens because these perisylvian centers are within the distribution of the MCA.
What is orbital medial syndrome?
Characterized by apathy which may occur in an extreme syndrom called akinetic mutism. Patients are motionless in their beds and don’t speak but often fllow the examiner aroun the room with their eyes. With vigorous stimulation, they will walk and speak.
