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What are the two main subdivisions of the cortex?
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What are the two subdivisions of the Allocortex and what does each contain?
- Paleocortex: olfactory tubercle, piriform cortex
- Archicortex: hippocampus, amygdala
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Part of the Archicortex of the Allocortex is the hippocampus. What are the 3 layers of the hippocampus?
- Dendrites
- Pyramidal Cell Bodies
- Axons
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NEOCORTEX Layer 1
Name
Cell Type
Function
- Molecular Layer
- Axons, dendrites
- Recieves Input
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NEOCORTEX Layer 2
Name
Cell Type
- External Granule Layer
- Small Round Cells
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NEOCORTEX Layer 3
Name
Cell Type
Function
- External Pyramidal Layer
- Small Pyramidal Cells
- Projects
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NEOCORTEX Layer 4
Name
Cell Type
Function
- Internal Granule Layer
- Small Round Cells
- Non-existent in motor cortex, very large in sensory cortices
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NEOCORTEX Layer 5
Name
Cell Type
Function
- Internal Pyramidal Layer
- Large Pyramidal Cells
- Projects
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NEOCORTEX Layer 6
Name
Cell Type
Function
- Polymorphic Layer
- Heterogeneous cells, fibers, blends into white matter
- Projects and recieves input
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How is the NeoCortex Organized?
- anatomical as well as functional
- ALSO know that the somatosensory and auditory cortices are organized like columns found in visual cortex
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What is the primary cortex?
- Where the sensory information comes in and/or where the motor information leaves the cortex
- If any deficits happen here, you will know about them
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What is the Association Cortex?
- Where the information gets put together
- Deficits here are discrete, subtle, and require specialized tests
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What is an example of a global function of the Neocortex?
learning/memory
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What is an example of a site specific function of the global cortex?
face recognition
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What is the difference between the unimodal areas and multimodal areas of the association cortex?
- The unimodal areas are right next to primary areas and when you injure them, the deficits are obvious
- The multimodal areas make up most of the cortex and are the prefrontal, parietla and temporal cortices. Deficits in these are not so obvious.
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What connects the association cortices together?
- Corpus Callosum
- Superior orbitofrontal fasciculus
- Arcuate fasciculus
- Inferior Occipoitofrontal Fasciculus
- Uncinate Fasciculus
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What is the dominant hemisphere in most people?
Left Hemisphere
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How do you determine what hemisphere is dominant and what hemisphere is non-dominant in a patient?
- The Wada Test: inject Barbituates into Interal Carotid
- Skilled motor tasts using both sides, speech, and language are controlled by the dominant side
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What are the functions of the non-dominant hemisphere?
- complex visual-spatial skills
- sense of direction
- prosody (rhythym of speech)
- emotional significance
- music perception
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Somatosensory Cortex
Input
Location
Special Notes
- from Thalamus VPL, VPM
- Post-Central Gyrus
- homunculus representation, 3 parallel cortical maps
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What happens when there is a lesion in the Somatosensory Cortex?
- Sensory Deficits: contralateral loss of discriminative touch, joint position sense
- Accompanied by agraphesthesia (cannot recognize letter written in palm), astereoagnosia (keys in pocket), extinction (contralateral loss of touch when simultaneous stimulation)
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Somatosensory Association Cortex
Location
Parietal Lobe behind the Post-Central Gyrus
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Motor cortex
Location
Motor Homunculus
- Pre-Central gyrus
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What do lesions in the motor cortex result in?
UMN disease (paralysis/weakness, hyperreflexia, increased reflex tone)
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Pre-Motor Cortex
Location
Ahead of the Pre-Cenral Gyrus
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What is the result of a lesion in the pre-motor cortex?
Apraxia: inability to execute skill/learned movements.....how frusturating!
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What two parts of the eye cortex control eye movements?
- Frontal Eye Fields: contralateral saccades and projects to the superior colliculus
- Parieto-Occipito-Temporal: Ipsilateral Smooth Pursuit
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What does a bilateral lesion of the auditory cortex cause?
- cortical deafness: react to stimulus, but do not realize itaphasia
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Auditory Cortex
location
temporal lobe
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Visual Cortex
location
calcarine fissure/occipital lobe
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What do unilateral lesions cause in the visual cortex? Bilateral lesions?
- unilateral lesions: homonymous visual feild defects or scotomas (small defects)
- Bilateral lesions:
cortical blindness with anosognosia (denies disability)
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What is apraxia?
inability to preform learned, skilled movements
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Where would a lesion have to be to lead to apraxia?
- supplementary motor area
- corpus callosum
- parietal lobe
- cerebellum
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What is aphasia?
Disturbances in ability to communicate excluding deafness, impairments to vision, or vocal cord function
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What are the characteristics of Broca's aphasia?
- loss of fluency
- telegraphic speech
- distorted speech sounds,but words are correct
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What are the characteristics of Wernicke's Aphasia?
fluent, un-intelligble speech, including paraphasias (wrong word or phoneme)
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What connects Wernicke's area and Broca's area?
arcuate fasciculus
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What is the difference between conduction aphasia and Wernicke's aphasia?
- Conduction Aphasia there is comprehension intact
- lesion is behind temporal lobe
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What are the characteristics of Transcortical Aphasia?
non-fluent speech, but repitition is spared
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What causes Global Aphasia?
Massive damage in the MCA on the left side
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What are the 4 characteristics of global aphasia?
- speech comprehesion blocked
- speech articulation blocked
- automatic speech only
- usually accompanied by right sided facial weakness
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Inferior Occipito-Temporal Cortex
Location
Function
- Inferior Occipio-temoral cortex
- Face Recognition/association of color
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What is the purpose of the frontal lobe? What are they important for?
- They are the major assocation cortex-- interconnections with most of the rest of the brain
- Restraint, initiative, order
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What are two frontal lobe syndromes?
- Orbitofrontal
- Dorsolateral prefrontal
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What does a lesion in the orbitofrontal portion of the frontal lobe cause?
- behavioral disinhibition
- hyperkinesia
- disruption of social behavior
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What does a leasion in the dorsolateral prefrontal region of the frontal lobes cause?
- psychomotor retardation
- hypokinesia
- Abulia: lack of initiative
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What is Balint's Syndrome?
- a bilateral lesion in the Dorsolateral Parieto-Occipital Cortex
- causes simultagnosia which is imparied ability to perceive a whole visual scene as a whole, optic ataxia which is impaired ability to reach for objects under visual guidance, ocular apraxia which is impaired ability to direct gaze through saccades
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Where is the knowledge of body in space located?
Posterior Parietal Cortex
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What happens if you have a right sided lesion of the posterior parietal cortrex?
- left sensory neglect
- you might run your left side into a door! or swear someone else is in your bed
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What can cause recovery of loss of some symptoms after a stroke?
Cortical Plasticity
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What lies in the future for Adult CNS Neurogenesis?
Well, we used to think that no new neurons were created after birth, but this is likely wrong and in the future Neurogenesis might be possible.
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