2 - Cerebral Cortex Flashcards
What does the cortex receive input from?
The Thalamus!
By 18 years of age, our brains way their full adult size of ____ grams.
1,400 grams
What is the cerebral cortex embryologically derived from?
The telencephalon.
What three parts can the telencephalon be subdivided into?
- Archicortex: hippocampus and dentate gyrus
- Paleocortex: olfactory cortex
- Neocortex
The cerebral cortex is made up of three poles and 6 lobes, name these?
3 poles: frontal, occipital, and temporal
6 lobes (4 major lobes and 2 subdivisions): Frontal, parietal, temporal, and occipital lobes. Insula and the limbic subdivisions.
What is the major arterial blood supply of the cerebral cortex?
Components of the Circle of Willis:
- ACA
- MCA
- PCA
- Anterior communicating a.
- Posterior communicating a.
What is the major venous drainage of the cerebral cortex?
Superior sagittal sinus
Inferior sagittal sinus
Straight sinus
Transverse sinus
Sigmoid sinus
All drain into the Internal Jugular Veins
How many cell layers are the Archicortex and the Neocortex?
Archicortex (hippocampus and dentate gyrus): 3 layers
Most of the cortex (neocortex): 6 cellular layers
What are the six cellular layers of the cortex (neocortex) from outermost to innermost?
- Molecular layer
- External granular layer
- External pyramidal layer
- Internal granular layer
- Internal pyramidal layer
- Multiform layer
What are the major cell types in the cortex?
Pyramidal cells and non-pyramidal cells (mixture of cell types).
What are the functional units of the cortex? Describe their organization and connections.
Columns and modules.
Columns extend through 6 layers that share similar functions and functional columns form modules in various cortical areas (especially the primary somatosensory, visual, and auditory cortices).
Columns of cortical neurons are interconnected with the same hemisphere and beterrn the two hemispheres.
What Broadmanns areas are in the dark blue on the left? What is its function?
Areas 44 and 45 - part of inferior frontal gyrus: motor area of speech
Broca’s area: mostly dominant in the left hemisphere
What Broadmanns area is in the lighter blue? What is its function?
Area 4 - precentral gyrus
Promary motor cortex
What Broadmanns areas are in red? What is its function?
Areas 3, 2, and 1 - postcentral gyrus
Primary somatosensory cortex
What Broadmanns areas are in yellow? What is their function?
Areas 41 and 42 - Transverse gyri of Heschl
Primary auditory cortex
What Broadmanns area is in green? What is its function?
Area 17 - Cuneus and Lingual gyri
Primary visual cortex
Describe the somatotopy of the postcentral gyrus? What Brodmann’s areas is it? What results frrom lesions in this area?
Areas 3, 2, and 1 : primary somatosensory cortex
Lower limb medial, hands and face have a large representation and are more lateral.
Lesions cause CONTRA loss of somesthetic (sensory) sensations
Describe the somatotopy of the precentral gyrus? What Brodmann’s areas is it? What results from a lesion in this area?
Area 4 - primary motor cortex
Motor humunculus has greater representation of the face and hand (lateral). Lower limb is medial.
Lesions result in CONTRA spastic paralysis.
Describe the somatotopy of the primary visual cortex? What Brodmann’s areas is it?
Area 17 (cuneus and lingual gyri)
Central visual field is most posterior, peripheral visual field is most anterior. Vertical meridian is at the border of areas 17 and 18. The horizontal meridian bisects horizontally.
What results from lesions to the primary visual cortex (area 17)? What about if the lesion is restricted to the upper or lower banks of the calcarine fissure?
Contralateral hemianopia.
If the lesion is restricted to the upper or lower banks of the calcarine fissure: contralateral inferior or superior quadrantanopia.
Describe the organization of the primary auditory cortex? What Brodmann’s areas is this? What results from bilateral lesions here?
Tonotopic organization (tones that are similar are closer together) and biaural representation (from both ears).
Bilateral lesiosn lead to loss of hearing.
What isthe significance of Brodmann’s areas 44 and 45?
Broca’s area: motor area of speech. Dominant mainly on the left side.
What occurs with a dominant side (left) lesion of Broca’s area? What results from a non-dominant (right) lesion of Broca’s area?
Dominant side (left) lesion: motor aphasia, Broca’s aphasia or expressive aphasia (can comprehend language but cannot speak properly.
Non-dominant (right) lesion: difficulty in expressing emotional aspect of language
What are the main functional areas of the frontal cortex?
- Primary motor cortex (4)
- Premotor cortex (6)
- Supplementary motor area
- Frontal eye field
- Broca’s area
- Limbic orbitofrontal cortex
- Prefrontal cortex
What are the functions of the prefrontal cortex?
Higher cortical function such as judgement, mathematical analysis, processing of information, emotion, behavior, and understanding social norms.
Lateral portion is for working memory (ie making a phone call, remembering the number for a short amount of time)
ventro-medial portion is orbito-frontal and is associated with the limbic system.
What are the association cortical areas of the parietal lobe? What Brodmann’s areas are they associated with?
Posterior parietal lobe: polymodal convergence
Superior parietal lobule: areas 5 and 7
Inferior parietal lobule: Supramarginal gyrus (area 40) and angular gyrus (area 39)
What results from a lesion to the dominant hemisphere of the parietal association cortical areas?
Dominant is usually the left hemisphere and can result in:
- asteriognosis (area 40) - don’t recognize meaning of things you touch
- aphasia: alecia and agraphia (area 39) - difficulty in reading and writing
What results from lesions to the non-dominant hemispheres of the parietal association cortical areas?
Non-dominant is usually rhe right hemisphere and results in:
- Spatial distortion
- Contralateral neglect
What are the association cortical areas of the occipital lobes? What Brodmann’s area is each? What results from a lesion here?
Secondary visual cortex: area 18 or V2
Associatal cortial areas: V3, V4, etc. (subdivisions of 19)
32 visual areas in the primate - occipital, parietal, and temporal
Lesions here result in a variety of visual defects.
What association cortical areas are in the temporal lobe? What is it’s function?
Wernicke’s area: posterior part of the superior temporal gyrus (area 22) invovled in language conprehension - dominant on left.
What results from lesiosn to Wernicke’s area in the dominant hemisphere?
Left hemisphere is dominant one.
Lesions here result in sensory aphasia, wernicke’s aphasia, or receptive aphasia.
Inability to comprehend language.
What results from lesiosn to Wernicke’s area in the non-dominant hemisphere?
Non-dominant side is the right side.
Lesions here result in difficulty comprehending the emotional aspect of language.
What are the major connections of the cerebral cortex?
There’s reciprocal connections with specific thalamus nuclei and cortico-cortical connections within the same hemisphere and between the two hemispheres.
Cortico-cortical connections are through short association fibers, long association fibers, and callosal fibers.
What is the general functional significance of the cerebral cortex?
- Perception of special sensations: somatic, visual, auditory, and olfaction
- Planning and excecution of voluntary movements
- Emotions and behavior
- Mental functioning
- Memory
Dysfunction of the cerebral cortex is usually caused by what?
Vascular hemorrhage, thrombosis, or tumor.
Tumor is generally of glial origin.
Lesion of the primary motor cortex results in _______ ________?
Contralateral paralysis.
Lesion of the primary sensory cortex results in what?
Contralateral loss of somatic sensation.
Lesion of the supramarginal gyrus (area 40) results in _______?
Astereognosis - is the inability to identify an object by active touch of the hands without other sensory input.
Lesion of the angular gyrus (area 39) results in _____ and ______?
Alexia - inability to read
Agraphia - inabiltiy to write
Lesion of Broca’s area (44 and 45) on the dominant side results in _______ ______?
Motor aphasia
