NS 71: The Cortex

What are the two main subdivisions of the cortex?


What are the two subdivisions of the Allocortex and what does each contain?

Paleocortex: olfactory tubercle, piriform cortexArchicortex: hippocampus, amygdala

Part of the Archicortex of the Allocortex is the hippocampus. What are the 3 layers of the hippocampus?

DendritesPyramidal Cell BodiesAxons

NEOCORTEX Layer 1NameCell Type Function

Molecular LayerAxons, dendritesRecieves Input

NEOCORTEX Layer 2NameCell Type

External Granule LayerSmall Round Cells

NEOCORTEX Layer 3NameCell Type Function

External Pyramidal LayerSmall Pyramidal CellsProjects

NEOCORTEX Layer 4NameCell Type Function

Internal Granule LayerSmall Round CellsNon-existent in motor cortex, very large in sensory cortices

NEOCORTEX Layer 5NameCell Type Function

Internal Pyramidal LayerLarge Pyramidal CellsProjects

NEOCORTEX Layer 6NameCell Type Function

Polymorphic LayerHeterogeneous cells, fibers, blends into white matterProjects and recieves input

How is the NeoCortex Organized?

anatomical as well as functionalALSO know that the somatosensory and auditory cortices are organized like columns found in visual cortex

What is the primary cortex?

Where the sensory information comes in and/or where the motor information leaves the cortexIf any deficits happen here, you will know about them

What is the Association Cortex?

Where the information gets put togetherDeficits here are discrete, subtle, and require specialized tests

What is an example of a global function of the Neocortex?


What is an example of a site specific function of the global cortex?

face recognition

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 obviousThe multimodal areas make up most of the cortex and are the prefrontal, parietla and temporal cortices. Deficits in these are not so obvious.

What connects the association cortices together?

Corpus CallosumSuperior orbitofrontal fasciculusArcuate fasciculusInferior Occipoitofrontal FasciculusUncinate Fasciculus

What is the dominant hemisphere in most people?

Left Hemisphere

How do you determine what hemisphere is dominant and what hemisphere is non-dominant in a patient?

The Wada Test: inject Barbituates into Interal CarotidSkilled motor tasts using both sides, speech, and language are controlled by the dominant side

What are the functions of the non-dominant hemisphere?

complex visual-spatial skillssense of directionprosody (rhythym of speech)emotional significancemusic perception

Somatosensory CortexInputLocationSpecial Notes

from Thalamus VPL, VPMPost-Central Gyrushomunculus representation, 3 parallel cortical maps

What happens when there is a lesion in the Somatosensory Cortex?

Sensory Deficits: contralateral loss of discriminative touch, joint position senseAccompanied by agraphesthesia (cannot recognize letter written in palm), astereoagnosia (keys in pocket), extinction (contralateral loss of touch when simultaneous stimulation)

Somatosensory Association CortexLocation

Parietal Lobe behind the Post-Central Gyrus

Motor cortexLocationMotor Homunculus

Pre-Central gyrus

What do lesions in the motor cortex result in?

UMN disease (paralysis/weakness, hyperreflexia, increased reflex tone)

Pre-Motor CortexLocation

Ahead of the Pre-Cenral Gyrus

What is the result of a lesion in the pre-motor cortex?

Apraxia: inability to execute skill/learned movements.....how frusturating!

What two parts of the eye cortex control eye movements?

Frontal Eye Fields: contralateral saccades and projects to the superior colliculusParieto-Occipito-Temporal: Ipsilateral Smooth Pursuit

What does a bilateral lesion of the auditory cortex cause?

cortical deafness: react to stimulus, but do not realize itaphasia

Auditory Cortexlocation

temporal lobe

Visual Cortexlocation

calcarine fissure/occipital lobe

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)

What is apraxia?

inability to preform learned, skilled movements

Where would a lesion have to be to lead to apraxia?

supplementary motor areacorpus callosumparietal lobecerebellum

What is aphasia?

Disturbances in ability to communicate excluding deafness, impairments to vision, or vocal cord function

What are the characteristics of Broca's aphasia?

loss of fluencytelegraphic speechdistorted speech sounds,but words are correct

What are the characteristics of Wernicke's Aphasia?

fluent, un-intelligble speech, including paraphasias (wrong word or phoneme)

What connects Wernicke's area and Broca's area?

arcuate fasciculus

What is the difference between conduction aphasia and Wernicke's aphasia?

Conduction Aphasia there is comprehension intactlesion is behind temporal lobe

What are the characteristics of Transcortical Aphasia?

non-fluent speech, but repitition is spared

What causes Global Aphasia?

Massive damage in the MCA on the left side

What are the 4 characteristics of global aphasia?

speech comprehesion blockedspeech articulation blockedautomatic speech onlyusually accompanied by right sided facial weakness

?Inferior Occipito-Temporal CortexLocationFunction

Inferior Occipio-temoral cortexFace Recognition/association of color

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 brainRestraint, initiative, order

What are two frontal lobe syndromes?

OrbitofrontalDorsolateral prefrontal

What does a lesion in the orbitofrontal portion of the frontal lobe cause?

behavioral disinhibitionhyperkinesiadisruption of social behavior

What does a leasion in the dorsolateral prefrontal region of the frontal lobes cause?

psychomotor retardationhypokinesiaAbulia: lack of initiative

What is Balint's Syndrome?

a bilateral lesion in the Dorsolateral Parieto-Occipital Cortexcauses 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

Where is the knowledge of body in space located?

Posterior Parietal Cortex

What happens if you have a right sided lesion of the posterior parietal cortrex?

left sensory neglectyou might run your left side into a door! or swear someone else is in your bed

What can cause recovery of loss of some symptoms after a stroke?

Cortical Plasticity

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.