Neocortex
The major part of the cerebral cortex consists of up to six horizontal layers, each with a different composition in terms of neurons and connectivity.
It is referred to as grey matter as it consists of cell bodies and capillaries and contrasts with the underlying white matter, which mainly consists of the white myelinated sheaths of neuronal axons.
The phylogenetically most recent part of the cerebral cortex, the neocortex (also called isocortex), is differentiated into six horizontal layers.
The more ancient part of the cerebral cortex, the hippocampus, has at most three cellular layers.
Neurons in various layers connect vertically to form small microcircuits, called cortical columns. Different neocortical regions known as Brodmann areas are distinguished by variations in their cytoarchitectonics (histological structure).
Neocortex Classification
2. Classification by Function
| Type | Main Role | Examples |
|---|---|---|
| Sensory Cortex | Processing sensory input | V1, A1, S1 |
| Motor Cortex | Voluntary movement control | M1 |
| Association Cortex | Integration, cognition, language | Prefrontal cortex, temporal association areas |
3. Classification by Region (Lobe-Based)
| Lobe | Main Functions |
|---|---|
| Frontal Lobe | Executive functions, motor control, speech |
| Parietal Lobe | Somatosensory processing, spatial skills |
| Temporal Lobe | Auditory processing, memory |
| Occipital Lobe | Visual processing |
4. Classification by Cytoarchitecture (Brodmann Areas)
- Classification based on cellular structure. - Examples:
- BA 4: Primary motor cortex
- BA 17: Primary visual cortex
- BA 41: Primary auditory cortex
- BA 44–45: Broca’s area
5. Specialized Types of Neocortex
| Type | Characteristics |
|---|---|
| Homotypical Neocortex | Well-defined six layers (typical structure) |
| Heterotypical Neocortex | Modified layering (granular or agranular) |
Summary
The neocortex is classified by function, anatomical region, and microscopic structure, reflecting its complexity and specialization.