Cerebral Cortex I

Question 1

Label the lateral and saggital brains.

Answer 1

See slide 5. (cingulate gyrus is right above corpus callosum)

Question 2

What is the “role” of the cerebral cortex?

Answer 2

analyzes, plans, initiates response

sensory pathways - “brings” in information
reticular system- adjusts its level of responsiveness (sometimes is turning system on sometimes shuts off)

Question 3

Describe the three types of cortex:

Answer 3

neocortex- most of cortex (6 layers)
archicortex- hippocampus (3 layers)
paleocortex - telencephalon base, olfactory (3-5 layers)

Question 4

Describe the composition of the neocortex.

Answer 4

human brain is about 86 billion nerve cells (18 percent in cerebral cortex)
cerebral cortex (GM + WM) is about 82 percent of brain mass
80 percent are pyramidal cells (give rise to axons that connect to other cortical structures or descending pathways)
20 percent are non pyramidal

Question 5

Describe pyramidal cells.

Answer 5

long apical dendrite and a basal dendrite

• axons leave cortex; excitatory (glutamate)
• dendritic spines - selectively modified by learning

Question 6

Describe the characteristics of non-pyramidal cells.

Answer 6

(think about as interneurons - make different connections between cells and give rise to different pathways)

• various shapes or appearances
• axons don’t leave the cortex; inhibitory (inhibitory neurotransmitter GABA released by these non-pyramidal cells)
• “interneurons” of the cerebral cortex

Question 7

How many layers does the neocortex have? Describe the two main areas.

Answer 7

Six layers

based upon how stained
agranular areas- large pyramidal cells
granular areas (koniocortex) -small neurons

Question 8

What are Brodmann’s Areas for precentral gyrus and postcentral gyrus?

Answer 8

precentral gyrus- area 4

postcentral gyrus - 3 1 2

Question 9

Describe the neocortex layers.

Answer 9

6 layers…
“efferents” tend to leave from lower levels like brainstem, spinal cord, corticostriate, thalamus… (most projections that leave leave from lower levels because that’s where pyramidal cells are
(non pyramidal cells are like interneurons- they don’t project out of the brain, but do connect neurons to one another)

“afferents” tend to end up in upper layers (cortical areas) because that’s where apical dendrite is: turns on/off

Question 10

How are cells in the neocortex arranged?

Answer 10

in columns

embryonic … from surface of embryonic brain to ventrical part of it these neuron stem cells/radioglial cells develop “ladders” …then neuroblasts (neuronal progenitors/primitive neurons) jump on the ladders and climb up and deposit self on different layers within the cerebral cortex (see slide 11)

Radial cells give rise to glial cells and help make myelin/Schwann cells

so columns that are close have similar functions, far away columns have different functions in the cerebral cortex

Question 11

Describe the function of the corpus callosum.

Answer 11

projects from cortical area to mirror image and other areas (white matter tracts)
hooks up right and left hemispheres

Question 12

Describe the parts of the corpus callosum.

Answer 12

genu- frontal lobes
anterior body- frontal lobe
posterior body- parietal lobe
splenium - occipital and temporal lobe

Question 13

What does the anterior commissure do?

Answer 13

interconnects temporal lobe and component’s of olfactory system

Question 14

What are association bundles or fasciculi?

Answer 14

(can dissect out)
tighter bundles of fibers connecting parts of the cerebral cortex

-corticocortical connections in the same hemisphere
-none are discrete point-to-point
fibers travel in both directions, leaving and entering

(ex: superior occipitofrontal fasciculus, superior longitudinal fasciculus (arcuate), inferior occipitofrontal fasciculus, uncinate fasciculus

Question 15

What is the location in the brain and Brodmann’s number that corresponds with the following functions?

primary motor-
primary somatosensory-
primary visual-
primary auditory-

(primary gustatory and primary vestibular)

Answer 15

primary motor- precentral gyrus, (4)

primary somatosensory- postcentral gyrus (3 1 2) (note- not occupying that much area in brain, most of cortex is doing something else)

primary visual- calcarine (17)

primary auditory- transverse temporal gyrus (41)

(primary gustatory- anterior insula? and primary vestibular- posterior insula?)

Question 16

Describe the unimodal association areas.

Answer 16

These are more complex response functions
adjacent to primary cortical areas, same “function, but less precise” body maps, injury can cause an agnosia (see a comb but have no idea what it is, can use other sensory info though to figure it out)

• Premotor (6) involves larger groups of muscles in an activity
• Supplementary motor (6) - assumption of postures or using muscles on both sides of the body
• Somatosensory (5,7)
• Visual (18. 19 +others?)

Question 17

Describe the unimodal association areas on a lateral section of a brain.

Answer 17

See slide 21.

Question 18

Describe multimodal association areas.

Answer 18

“high level intellectual functions” - association areas send converging inputs; may respond to multiple stimuli or under particular circumstances. Injury can cause an apraxia (motor) or neglect (sensory)

(neglect is an injury that causes them to forget L side of body for instance)

Examples:
parieto-occipital-temporal region, prefrontal area, limbic area

Question 19

Describe the parieto-occipital-temporal region.

Answer 19

Ex. of multimodal association areas

• surrounded by sensory areas and also receives input from the pulvinar
• injury to the right inferior parietal lobule can cause contralateral neglect
• injury to the left parietal area can cause an apraxia

(see slide 24)

Question 20

Describe the prefrontal area. (Dorsolateral and ventromedial sections and function)

Answer 20

Ex. of multimodal association areas

Dorsolateral - more important for working memory, attention, and logical aspects of problem solving

Ventromedial- has extensive limbic connections and are more important for emotional aspects of planning and decisions

Executive functions of the brain- planning, insight, foresight and basic aspects of personality

Question 21

Describe the limbic area.

Answer 21

emotional and “drive” related behaviors (see slide 25)

Question 22

The corpus callosum unites the two cerebral hemispheres and “all” cortical areas receive CC commissural fibers except three areas. What are they?

Answer 22

• hand area of somatosensory and motor cortex
• area 17; those areas not representing the area adjacent to the vertical midline
• temporal lobe; connections between lobes pass through the anterior commissure (REMEMBER)

Question 23

Describe disconnection syndromes.

Answer 23

often result from white matter damage that interferes with these connections
Ex: alexia without agraphia (person with normal language function cannot read but can still write… can’t read what they wrote but can trace letters and figure it out - can still see it)

Question 24

Describe alexia without agraphia in more detail.

Answer 24

disconnection syndrome - can’t read but can write
(most people are L hemisphere dominant for language- Wernicke’s and Broca’s areas are here) so damage on L will mean aphasia, damage on R, still have most language)

if there is damage across the corpus callosum (bc of this stroke of PCA in L occipital lobe which resulted in loss of R visual field) … then this person can see words but cant transmit information across the corpus callosum and could write but not interpret words visually. Can still understand langauge (Broca’s Wernicke’s still in tact)

L occipital lobe sees R visual field - so if there is stroke of PCA on L occipital lobe then the person can’t see R field