1
Q
Cerebral Cortex:
Anatomical organization
A
- Embryologically derived from the telencephalon
- Can be subdivided into:
- Archicortex (3 layers)
- Hippocampus and Dentate gyrus
- Paleocortex
- Olfcatory cortex
- Neocortex (6 layers)
- Archicortex (3 layers)
- Made up of 3 poles (frontal, occipital, and temporal) and 6 lobes
2
Q
6 Anatomical Lobes:
A
- Frontal lobe
- Parietal lobe
- Temporal lobe
- Occipital lobe
- Insular lobe
- The Insula
- Limbic lobe:
- includes Cingulate gyrus, Parahippocampal gyrus, and Hippocampus
3
Q
Blood supply to the cerebral cortex:
A
- Anterior cerebral
- Middle cerebral
- Posterior cerebral
- Anterior communicating
- Posterior communicating arteries
- all of which form the Circle of Willis
4
Q
Drainage of the cerebral cortex:
A
- Superior Sagittal sinus
- Inferior sagittal sinus
- Straight sinus
- Transverse sinuses
- Sigmoid sinuses
- which drain into the Internal jugular veins
5
Q
6 Layers of the Neocortex:
A
- Layer I: Molecular layer
- Layer II: External granular layer
- Layer III: External pyramidal layer
- Layer IV: Internal granular layer
- well-developed in sensory areas
- Layer V: Internal pyramidal layer
- well-developed in motor areas
- Layer VI: Multiform layer
- project back to the thalamus
6
Q
How are myelinated axons organized in the cortex?
A
horizontal bands and vertical bundles
7
Q
What are the major cell types of the cortex?
A
Pyramidal and Non-pyramidal
8
Q
Functional units: Columns and Modules
A
- Each column extends through the 6 layers that share similar functions
- Functional columns form modules in various cortical areas
- especially the primary somatosensory, visual, and auditory cortices
- Columns of cortical neurons are interconnected within the same hemisphere and between the two hemispheres
9
Q
Areas 3, 1, 2 (Postcentral gyrus):
A
Primary somatosensory cortex
- Somatotopic organization (contralateral)
- Sensory homunculus
- Greater representation of the face and hand
- Lower limb representation is medial
- Lesion:
- Contralateral loss of somesthetic sensation
10
Q
Area 4 (Precentral gyrus):
A
Primary motor cortex
- Somatotopic organization (contralateral)
- Motor homunculus
- Greater representation of the face and hand
- Lower limb representation is medial
- Lesion:
- Contralateral spastic paralysis
11
Q
Area 17 (Cuneus and Lingual gyri):
A
Primary visual cortex
- Visuotopic organization
- Central visual field: Most posterior
- Peripheral visual field: most anterior
- Vertical meridian: border of areas 17 and 18
- Horizontal meridian: bisect horizontally
- Lesions:
- Contralateral hemianopia
- If restricted to upper or lower banks of the Calcarine fissure ⇒ contralateral inferior or superior quadrantanopia
12
Q
Areas 41 and 42: Transverse gyri (of Heschl)
A
Primary auditory cortex
- Tonotopic organization
- Biaural representation
- Lesions:
- Bilateral lesions lead to loss of hearing
13
Q
Areas 44 and 45: part of the **Inferior frontal gyrus **
A
Motor area of speech (Broca’s area)
- mostly dominant in the left hemisphere
- Lesions:
- Dominant side (left) ⇒ motor aphasia, Broca’s aphasia, or expressive aphasia
- Non-dominant (right) ⇒ difficulty in expressing emotional aspect of language
14
Q
Main functional areas of the frontal cortex:
A
- Primary motor cortex: area 4
- Premotor cortex: area 6
- Supplementary motor cortex
- Frontal eye field
- Broca’s area
- Prefrontal cortex:
- Dorsolateral prefrontal cortex: working memory
- Ventromedial prefrontal cortex (orbitofronal cortex): limbic
15
Q
Association cortical areas of the parietal lobe:
A
- Posterior parietal lobe: polymodal convergence
- Superior parietal lobule: areas 5 and 7
- Inferior parietal lobule: Supramarginal gyrus (area 40) and Angular gyrus (area 39)
Lesions:
- **Dominant (usually left) hemisphere: **
- astereognosis (area 40)
- lose the meaning of touch
- aphasia, alexia and agraphia (area 39)
- inability to read and write
- astereognosis (area 40)
- Non-dominant (usually right) hemisphere:
- spatial distortion
- contralateral neglect
16
Q
Assciation cortical areas of the occipital lobe:
A
- Secondary visual cortex: area 18 or V2
- Association cortical areas: V3, V4, etc.
- 32 visual areas in the primate cortex (in the occipital, parietal, and temporal cortices)
Lesions:
- A variety of visual deficits
17
Q
Association cortical areas of the temporal lobe:
A
- Wernicke’s area: Posterior part of the superior temporal gyrus (area 22)
- language comprehension (dominant on the left)
Lesions:
- Wernicke’s area (dominant hemisphere)
- sensory aphasia, Wernicke’s aphasia, or receptive aphasia
- Wernicke’s area (non-dominant hemisphere)
- difficulty in comprehending the emotional aspect of language
18
Q
Cortico-cortical connections within the same hemisphere and between the two hemispheres:
A
- Short association fibers
- Long association fibers
- Callosal fibers
19
Q
GENERAL FUNCTIONAL SIGNIFICANCE OF THE CEREBRAL CORTEX:
A
- Perception of special sensations: somatic, visual, auditory, olfaction
- Multiple cortical maps for each of the major sensory representation
- Planning and execution of voluntary movements
- Emotions and behavior
- Mental functioning
- Memory
20
Q
DYSFUNCTIONS OF THE CEREBRAL CORTEX:
A
- Dysfunction is usually caused by vascular hemorrhage, thrombosis, or tumor
- Tumor is generally of glial origin
- Symptoms are related to specific region(s) of the cortex being affected
21
Q
Examples of cortical dysfunction:
A
- Lesion of primary motor cortex:
- Contralateral paralysis
- Lesion of primary sensory cortex:
- Contralateral loss of somatic sensation
- Lesion of primary visual cortex:
- Contralateral hemianopia
- Lesion of the supramarginal gyrus (area 40):
- astereognosis
- Lesion of the angular gyrus (area 39):
- alexia and agraphia
- Lesion of the Broca’s area (44 and 45) on the dominant hemisphere:
- motor aphasia
