Cerebral Cortex Flashcards
What is the average thickness of the gray matter of the cortex?
Where is it thickest and thinnest?
2.5mm
Range:
- 5mm at the occipital cortex
- 5mm at the primary motor cortex
What are the 3 types of cortices?
- Isocortex: 6 layers– primary sensory and motor cortex
- Mesocortex (Paleocortex, Archicortex): Intermediate– cingulate gyrus, parahippocampal cortex
- Allocortex: 3 layers– primary olfactory cortex and hippocampal formation
What is the only cortical layer without pyramidal neruons?
1
What are the types of principal neurons?
How about interneurons?
Pyramidal and Fusiform
Stellate or granule cells, Horizontal Cells of Cajal, Cells of Martinotti
What is the only excitatory interneuron?
Stellate or granule neuron– Secretes glutamate
ALL OTHERS ARE GABA SECRETING
The neurons of all six layers of the cortex develop in waves from?
When are they first recognizable?
The periventricular germinal matrix
All six layers are recognizable by 7 months of intrauterine life
What cortical layer?
- Are the stripes of Kaes-Bekhterev found
- Stripe of Gennari and band of baillarger
- Main recepient of the thalamocortical fibers
- Lowest cell packing density and location of the BEtz cells
- Internal band of Baillarger
- Cells of Martinotti are prominent here
- Layer 3 External pyramidal
- Layer 4 IN THE VISUAL CORTEX– hence the name striate cortex!
- Layer 4 Internal Granular
- Layer 5 Internal Pyramidal
- Layer 5 Internal pyramidal layer– these are form thalamic sensory nuclei thus the band IS MOST PROMINENT IN PRIMARY CORTICAL SENSORY AREAS
- Layer 6 Multiform layer
What cortical layer/s?
- Present in all types of cortex
- Present in neocortex
- Mainly receptive
- Mainly efferent
- 1 5 6
- 2 3 4
- 1 2 3 4
- 5 6
Where do these monoaminergic inputs mainly come from
- Serotonergic
- Dopaminergic:
- Noradrenergic input
- Cholinergic input
- Serotonergic: Raphe nuclei in them midbrain and pons– role in pain control, sleep and emotion
- Dopaminergic: Ventral tegmental area of tsai and the substantia nigra of the mesencephalon– role in orienting behavior
- Noradrenergic input: Locus ceruleus in the rostral pons– arousal state
- Cholinergic input: Nucleus basalis of Meynert– arousal and motivation
Which association fiber is being described?
- Connects the atnerior perforated substance with the parahippocampal gyrus
- Connects the frontal lobe with the parietal occipital and temporal lobes
- Sweeps around the insula to connect the inferior frontal area (broca) with the superior temporal gyrus (wernicke)
- Connects adjacent regions of the occipital and temporal areas
- Connects the inferior frontal gyrus with the anterior temporal lobe
- Cingulate fasciculus: Connects the atnerior perforated substance with the parahippocampal gyrus
- Superior longitudinal fasciculus: Connects the frontal lobe with the parietal occipital and temporal lobes
- Arcuate fasciculus: Sweeps around the insula to connect the inferior frontal area (broca) with the superior temporal gyrus (wernicke)
- U fibers: Connects adjacent regions of the occipital and temporal areas
- Uncinate fasciculus: Connects the inferior frontal gyrus with the anterior temporal lobe
What are the commisural fiber systems?
Corpus callosum
Anterior commissure
Hippocampal commissure
Which areas of the cortex innervate the lower subnucleus of the nuclei of CN7 of the contralateral side?
How about those that go to both upper subnuclei?
- Primary motor cortex, caudal cingulate gyrus
2. Supplementary motor cortex, rostral cingulate gyrus
Which parts of the cortex subserve EMOTIONAL expresssion?
Cingulate gyrus
Identify the Brodmann area:
Post central gyrus
Precentral gyrus
Primary visual cortex
Superior temporal gyrus, auditory association area (Wernicke’s)
Heschl’s gyrus, primary auditory cortex
Pars opercularis of the inferior frontal gyrus
Pars triangularis of the inferior frontal gyrus
BOTH form the Broca’s area
Dorsal entorhinal area for olfaction, medial most temporal lobe
Insular cortex Island of Reil, frontoparietal rolandic operculum, gustatory cortex
Post central gyrus 1,2,3
Precentral gyrus 4
Primary visual cortex 17
Superior temporal gyrus, auditory association area (Wernicke’s) 22
Heschl’s gyrus, primary auditory cortex 41 42
Pars opercularis of the inferior frontal gyrus
Pars triangularis of the inferior frontal gyrus
BOTH form the Broca’s area 44 45
Dorsal entorhinal area for olfaction, medial most temporal lobe 34
Insular cortex Island of Reil, frontoparietal rolandic operculum, gustatory cortex 43
What is the most medial representation in the sensory homunculus
Anal and genital regions
Which brodmann areas are activated by different sensory stimuli?
1 both cutaneous or proprioreceptive
2 and 3a Proprioreceptive
3b cutaneous
What do lesions in the primary somatosensory association areas in the the superior parietal lobule B5 and 7 do?
Bilateral: Optic ataxia– unable to move hand toward an object that is seen
Unilateral: Neglect of the opposite side of the body
Why would a PCA infarct still have macular sparing?
Because of the collateral supply from the MCA to the macular area of the cortex
What are the dorsal and ventral stream outputs from the visual cortex?
Where do they go and what are they for?
Dorsal to the occipitoparietal cortex for the “where” pathway– lesion Balint Holmes syndrome inability to direct eyes ta certain point despite having intact eoms
Ventral to the occipitotemporal cortex for the “what” pathway– lesion visual agnosia inability to comprehend the meaning of nonverbal visual stimuli
ADD: Bilateral lesion in the inferior parietal lobule will cause Balint syndrome (Optic ataxia, oculomotor ataxia and psychic paralysis of visual fixation)
Stimulation of the primary auditory cortex results in?
Lesions there result in?
Tinnitus
Impairment in sound localization in space with diminution of hearing bilaterally
What is the function of Area 22 on the non-dominant hemisphere? Wernicke’s on the dominant side
Specializes in non speech auditory information: prosody– tonal qualities of sound, musical melodies
Where is the primary vestibular cortex?
lateral cortical temporoparietal area
B40 Supramarginal gyrus
B21 Middle temporal gyrus
B22 Superior temporal gyrus
What percentage of fibers in the corticospinal pyramidal tract is from the primary motor cortex? Originate directly from the giant motor neurons of Betz?
40%
3%
What is the function of the supplementary motor are? What percentage contributes to the pyramidal tract?
Sequential performance of multiple movements
5%
What apraxia results from destruction of the premotor area?
Ideomotor apraxia
Ideomotor apraxia: These patients have deficits in their ability to plan or complete motor actions that rely on semantic memory. They are able to explain how to perform an action, but unable to “imagine” or act out a movement such as “pretend to brush your teeth” or “pucker as though you bit into a sour lemon.”
Contrast with ideational apraxia: Ideational/conceptual apraxia: Patients have an inability to conceptualize a task and impaired ability to complete multistep actions. Consists of an inability to select and carry out an appropriate motor program. For example, the patient may complete actions in incorrect orders, such as buttering bread before putting it in the toaster, or putting on shoes before putting on socks. There is also a loss of ability to voluntarily perform a learned task when given the necessary objects or tools.
Besides the FEF what other cortical area is concerned with smooth pursuit?
Temporooccipitoparietal cortex
What percentage of left handed people will be left dominant?
2/3
Besides the posterior portion of the superior temporal gyrus what is the other part of Wernicke’s area not originally described by the founder?
Angular gyrus B39
While 22 is for comprehension of spoken language
39 is for written language
What connects the Broca’s and Wernicke’s areas?
Arcuate fasciculus
Where is Broca’s area?
Posterior part of the triangular gyrus B45 and the opercular gyrus B44 in the inferior frontal gyrus
Lesion of “Broca” B44 in right will result in?
“Wernicke” B22 in right?
Dull monotonous speech
Unable to detect inflections in speech
The lesioned area in patients with the Gerstmann sydnrome is in the major association cortex. Where is this?
Inferior parietal gyrus on the dominant side
Supramarginal gyrus B40
Angular gyrus B39
What are the five major branches of the anterior cerebral artery?
Oribitofrontal branch Frontopolar branch Pericallosal branch --Callosomarginal branch --Paracentral branch
– branches of the pericallosal branch
What connects the vein of Trolard and the vein of Labbe?
The middle cerebral vein
Broca’s aphasia patients speak in 10 words or less per minute with paraphasia. What are paraphasias?
Ommission of phonenmes or substitution of incorrect phonemes.
Pem for pen
Ha for hall
NOTE THAT PARAPHASIA ALSO OCCURS IN WERNICKE’S
Differentiate transocortical sensory from Wernicke’s.
TS can repeat! But both have problems with auditory comprehension
Where is the lesion in conduction aphasia?
Posterior perisylvian area– can understand and speak but CANNOT REPEAT
Interrupts the arcuate fasciculus
Where is the lesion in anomic aphasia?
Inferior or anterior temporal
Thalamic lesions have what type of aphasia?
Similar to broca’s
While left basal ganglia have fluent, paraphasic and dysarthric speech– similar to Wernicke’s
What are the three anatomic locations of ideomotor apraxia?
Parietal
Sympathetic
Callosal
What is ideational apraxia?
Abnormality in the conception of movement so that the patient may have difficulty sequencing the different components of a complex motor act– such as in mailing a letter
What is alexia and where are the lesions?
Inability to comprehend written language
Without agraphia– left PCA infarcts
With agraphia– dominant angular gyrus
What are the three findings in Balint syndrome?
Ocular apraxia
Ocular ataxia
Simultagnosia
What are the 6 elements of Kluver Blucy Syndrome? (With temporal lobectomy)
- Blunted affect
- Psychich blindness or visual agnosia
- Hypermetamorphosis: Urge to notice everything in sight
- Hyperorality
- Bulimia
- Alteration in sexual behaviour
How to test for simultagnosia? A component of Balint’s syndrome
Show them a detailed picture. They will get the details right but they will be unable to get the meaning of the entire picture
Lesion in alien hand syndrome?
- Corpus callosum
2. Medial frontal lesion including the supplementary motor area
