Corpus: Cerebral cortex
from Latin: cortex - cortex, cerebrum - brain
1. Definition
The cerebral cortex is a part of the telencephalon. It consists of neuron cell bodies, forminig the gray matter. Afferent and efferent fibers from these neurons form the white matter, which is situated between the areas of gray matter.
2. Function
The cerebral cortex is the phylogenetically youngest and most developed brain region. It serves higher functions such as processing sensory perceptions, seeing, reading, hearing, speaking, planning and execution of voluntary movements, consciousness, complex thinking, personality, and more.
3. Structure
3.1. Topographical organization
The cortex can be roughly divided into five lobes:
The individual lobes are subdivided into convolutions (gyri), which are separated by sulci and fissures. Key structures include:
- Central sulcus
- Lateral sulcus
- Calcarine sulcus
- Parieto-occipital sulcus
- Longitudinal fissure separating the two cerebral hemispheres
3.2. Functional organization
Functionally, the cortex is divided into different regions (according to Brodmann). The most important regions include:
- Primary motor cortex (Area 4) for movement execution
- Secondary motor cortex (Area 6) for movement planning
- Primary visual cortex (Area 17)
- Auditory cortex or sensory speech center (Area 22)
- Motor speech center (Area 44)
- Somatosensory cortex (Areas 1, 2, 3)
- Supplementary cortical fields for information processing
- Limbic system
3.3. Histological layer structure
3.3.1. Isocortex
The isocortex has six layers from the outside to the inside:
- Molecular layer (Lamina molecularis, I)
- External granular layer (Lamina granularis externa, II)
- External pyramidal layer (Lamina pyramidalis externa, III)
- Internal granular layer (Lamina granularis interna, IV)
- Internal pyramidal layer (Lamina pyramidalis interna, V)
- Multiform layer (Lamina multiformis, VI)
The layer sIV (receiving afferents from the thalamus, among others) and V (containing Betz giant pyramidal cells, with efferents via pyramidal tracts, among others) are particularly important. The variations in histological structures are fundamental to the cytoarchitectonic mapping of the cerebral cortex.
3.3.2. Allocortex
The allocortex has three to five layers from the outside to the inside:
- Molecular layer
- Pyramidal layer
- Multiform layer
The allocortex can be subdivided into the paleocortex and the archicortex.
3.4. Associations
- Association fibers
- Projection fibers
- Commissural fibers
Nerve pathways that run to the cerebral cortex are called corticopetal pathways. If they run away from the cerebral cortex, they are corticofugal.