Organisation of Cerebral Cortex Flashcards
Grey Matter?
Neurons (50bn) Glial cells (500bn)
30% is visible
70% is hidden in the SULCI
White Matter?
Includes
o myelinated neuronal axons
which go on to form white matter tracts
3 types of White Matter fibres?
- Association fibres
o connect areas within the same hemisphere - Commissural fibres
o connect left hemisphere to right hemisphere - Projection fibres
o connect cortex with lower brain structures (e.g. thalamus), brainstem and spinal cord
What is the neocortex?
A new evolutional development that describes the 6 layers in the diagram!
a part of the cerebral cortex concerned with sight and hearing in mammals, regarded as the most recently evolved part of the cortex
ONENOTE!
How many Cortical layers are there in the Grey Matter?
6!
Layer 1 of the Grey Matter?
Contains mainly o neuropil (dense network of interwoven nerve fibres & glia)
Layer 2/3 of the Grey Matter?
Contains
o pyramidal neurons that have primary Cortico-cortical connections
Layer 4 of the Grey Matter?
Has mainly
o stellate neurones
o with local axons in the primary sensory cortices
o that RECEIVE input from the thalamus
Layer 5/6 of the Grey Matter?
Typically contain
o pyramidal neurons
o whose axons leave the cortex (there are about 50 distinct cortical regions)
- contains the large BETZ CELLS
Output/Inputs of the cortical layers of the Grey Matter?
Layer 1/2/3 = Output to CORTEX
Layer 4 = INPUT
Layer 5/6 = Output to NON-CORTEX
How are the neurones organised locally in the cortical layers?
Into COLUMNS
o along the columns, have dense vertical connections
o these neurones interact with one another
o basis for TOPOGRAPHICAL ORGANISATION
Brodmann’s Areas?
Split the cerebral cortex up into areas with distinct histological patterns & functions
i.e. (respond to same stimuli)
Explain the Association Fibres
WHITE MATTER
2 TYPES
o Short Association Fibres - connect SHORT distances
o Long Association Fibres = connect more DISTANT structure
LUDLEYS!!
Long Association Fibres?
White Matter - connect more distant structures
e.g.
o Super Longitudinal Fasciculus
- connects frontal & occipital lobes
o Arcuate Fasciculus
- connects frontal & temporal lobes
o Inferior Longitudinal Fasciculus
- connects temporal & occipital lobes
o Uncinate Fasciculus
- connects anterior frontal & temporal lobes
Function of Commissural and Projection Fibres?
WHITE MATTER
Commissural Fibres
o connect hemispheres e.g. corpus callosum
Projection Fibres
o long projections out of cortex e.g. internal capsule
Neocortex is comprised of different lobes - what are these lobes?
Frontal Lobe
Parietal Lobe
Occipital Lobe
Temporal Lobe
Occipital Lobe?
Vision Association Cortex
o Ventral pathway = form & colour
o Dorsal pathway = spatial relationships * movement
Parietal Lobe?
Posterior Parietal Association Cortex
o Spatial map of the body in the surroundings
Injury may cause
o disorientation
o inability to read a map
o inability to understand spatial relationships e.g. apraxia & neglect
Temporal Lobe?
Language, object recognition, memory & emotion
Injury leads to o Agnosia (inability to interpret sensations although sense organs & nerves are functioning normally)
o Receptive aphasia (inability to create speech)
Frontal Lobe?
Judgement, foresight, personality and appreciation of self in relation to the world
Injury leads to
o deficits in planning
o inappropriate behaviour
Primary Cortices?
Predictable function
Organised topographically
Left-right symmetry
Association Cortices?
Function less predictable
Not organised topographically
Left-right symmetry weak/absent
What helps in ‘Voluntary skeletal muscle movements’?
o Primary motor cortex
- precentral gyrus
o Premotor cortex
- motor association area
What helps in ‘Recognition & interpretation of sensory information from skin, muscles and taste buds’?
o Primary somatosensory cortex
- postcentral gyrus
o Sensory association area
BOTH = Parietal Lobe
