Cerebral Cortex -Bales Flashcards
What are the layers from superficial to deep of the cortex?
- molecular layer
- external granular layer
- external pyramidal layer
- internal granular layer
- internal pyramidal layer
- multiform layer
What are the regions of homotypical cortex?
relatively proportional layers
e.g. primary sensory
What are the regions of heterotypical agranular cortex?
pyramidal layers (3 and 5) are enlarged
e.g. primary motor cortex
What are the regions of heterotypical granular cortex?
layer 4 is enlarged
e.g. association cortex
What are some key features of pyramidal neurons?
- 75% of neurons
- small to large triangular bodies
- apex points to surface; apical dendrites extend to layer 1
- basal dendrites from each corner spread out more locally
- dendrites are spiny (spines receive synaptic input)
- all excitatory
- axon from center of base projects to white matter; often with collateral branches
Where are the largest pyramidal cells?
Betz cells in layer 5 of the primary motor cortex (BA4)
Where do abnormal products accumulate in Alzheimer disease?
In the pyramidal cells
association cortex and hippocampal pyramidal neurons are especially vulnerable
What are some properties of cortical interneurons?
- all smooth (except the spiny interneuron
- mostly inhibitory
- most small, irregular
What exists in layer 1?
afferent axon terminals and dendrites of pyramidal neurons
What exists in layer 2?
mostly small granular interneurons
What exists in layer 3?
- has the most terminations of cortical intrahemispheric association fibers
- plus significant callosal fiber input (interhemispheric)
- pyramidal cells project to cortex via callosal or association pathways
Which 2 layers have callosal fibers (inter hemispheric)?
layers 3 and 4
What exists in layer 4?
- significant callosal input
- main termination layer for specific thalamocortical fibers
- mostly small (granular) interneurons (not a main output layer)
- horizontal branches (of thalamocortical input) which form the “outer band of Baillarger”
Which layer is the stripe of Genarri found in?
layer 4
this is the outer band of Baillarger in the primary visual cortex (BA17=”striped cortex”)
What exists in layer 5?
- major output projection layer
- mostly medium-to-large-to-giant (Betz) pyramidal cells
- main output (corticofugal) layer to most subcortical targets
Which layer projects to all of the cortico paths?
layer 5
corticospinal, corticobulbar, corticopontine, corticostriate, corticorubral
What exists in layer 6?
- small pyramidal and modified pyramidal (fusiform) neurons
- main output layer for corticothalamic fibers
Which 2 reticular nuclei function in cortical arousal and alertness? What neurotransmitters do they produce?
Raphe nuclei are serotoninergic
locus ceruleus is norepinephrinergic
What is a major source of Ach neurons to the cortex?
Basal nuclear of meynert
fascilitates cortical memory functions
The majority of cortical interneurons are _______ to the pyramidal cells
inhibitory (GABAergic)
What is the most important cortical interneuron? Why?
the chandelier cell synapses strongly at the initial segment of the axon and is the last control point before the action potential
How many pyramidal axons can one chandelier cell axon terminate on?
MANY!
they are the principle regulators of cortical output
What would a lesion of the dominant left temporal lobe cause?
fluent aphasia due to the loss of wernickes
- can’t process auditory input
- inability to repeat a command
- can’t read aloud
What would a lesion of the right temporal lobe cause?
- amusia–> loss of musical ability
- loss of ability to appreciate the variable aspects of speech which add emotional and other non-word features (aprosodia)
What would an occipital lesion cause?
visual agnosia (inability to recognize familiar objects) or alexia (inability to recognize words)
What would an inferior occipital-temporal lobe lesion cause?
prosopagnosia–> inability to recognize faces
What is a Jacksonian march?
a seizure along the pre central gyrus which will begin with involuntary movement along the motor homunculus
the initial body part that moved would localize the origin of the seizure
What would a frontal lobe lesion cause?
apraxias: inability to perform a voluntary motor act in the absence of paralysis
Voluntary control of micturition seems to occur in a medial premotor area
What would a lesion to the frontal eye field cause? Stimulation?
lesion: horizontal deviation to the lesion side
stimulation: horizontal deviation to the opposite side
What are some believed functions of the insula?
- visceral homeostasis (both motor and sensory functions)
- crude (unlocalized) pain and temperature sense (collateral path of ALS)
- primary gustatory cortex (solitariothalamocortical pathway)
- vestibular cortex (among other places)
- limbic and olfactory association cortex
What is Gerstmann’s syndrome? What can cause it?
angular gyrus syndrome
Lesions, especially focused on angular gyrus, cause multiple affects including inability to write (agraphia), inability to do math (acalculia), inability to recognize and name individual fingers (finger agnosia) and inability to tell right-from left
What will a lesion of the right inferior parietal lobe cause?
astereognosis –> inability to recognize objects
What will a lesion of the right superior parietal lobe cause?
hemineglect of the left side of the body and world
What happens in Pick’s disease?
frontal and temporal lobes degenerate
“frontotemporal dementia”
