Organisation of Cerebral Cortex Flashcards
What are the three types of fibre that make up white matter?
- Association Fibres – connect with areas in the same hemisphere
- Commissural Fibres – connect the two hemispheres
- Projection Fibres – connect the cortex with lower brain structures (e.g. thalamus)
In humans, how many layers of grey matter are there?
Three to six cortical layers, which are usually designated by Roman numerals, with letters for laminar subdivisions
Distinguish between the terms ‘cortex’ and ‘neocortex’. Summarise the main function s of the neocortex
The neocortex has 6 horizontal layers of different neuronal structure, while the rest of cortex, called “allocortex” has 3 layers; in humans, almost all cerebral cortex is neocortex.
The neocortex is involved in higher functions such as sensory perception, generation of motor commands, spatial reasoning, conscious thought, and language
Describe the different connections of the 6 layers of grey matter.
Layers 1-3 = mainly cortico-cortical connections
Layer 4 = input from the thalamus
Layer 5-6 = connections with subcortical, brainstem and spinal cord
Note that the neocortex is also arranged in columns so that neurons with similar properties are connected in the same column; more dense vertical connections (basis for topographical organisation)
What does layer 1 mainly consist of?
Neutropil – an area composed mostly of unmyelinated axons, dendrites and glial cell processes that forms a synaptically dense region containing a relatively low number of cell bodies
What type of neurone is found in layer 4?
Stellate neurones;
in the primary sensory cortices, receive input from the thalamus
What type of neurone is found in layer 5, and to a lesser degree layer 6?
Pyramidal neurones whose axons typically leave the cortex
What are the two parts of the visual association cortex and what are they responsible for?
Dorsal Pathway – responsible for interpretation of spatial relationships and movements
Ventral Pathway – responsible for form and colour
What is the role of the posterior parietal association cortex?
It creates a SPATIAL MAP of the body in its surroundings from multi-modality information
What could injury of this part of the association cortex lead to?
- Disorientation
- Inability to read a map or understand spatial relationships
- Apraxia
- Hemispatial Neglect
Define apraxia.
Inability to make skilled movements with accuracy
What is the temporal association cortex responsible for?
- Language
- Object Recognition
- Memory
- Emotions
What are the two main consequences of injury to the temporal lobe?
AGNOSIA – inability for the brain to interpret sensory information although the nerves carrying sensory information to the brain are fine
E.g. visual agnosia – patients can see perfectly fine but they can’t interpret symbols such as letters
RECEPTIVE APHASIA –unable to understand language in the spoken or written forms
Name a consequence of a lesion of the visual association cortex (in fusiform gyrus)
Prosopagnosia – inability to recognise familiar faces or learn new faces
What is the role of the frontal lobe?
Executive functions e.g. planning, judgement, foresight, personality
