The Cerebral Cortex and the Neocortex

Cerebral Cortex

A 600 grams grey sheet constituting 40% of brain weight and containing 25 billion neurons.

Neurons

Cells in the brain that weigh about 180 grams, with additional glial cells and blood vessels weighing 420 grams.

Brodmann's Scheme

A system that numbers areas of the neocortex based on cytoarchitecture differences, known as Brodmann numbers.

Neocortex Layers

The neocortex is organized into 6 horizontal laminae/layers oriented parallel to the cortical surface.

Primary/Receptive Cortex

Includes primary sensory areas that directly receive thalamic input and can lose modality if damaged.

Secondary Association Cortex

Responsible for processing, integration, and interpretation of information from the primary cortex; damage can cause agnosia.

Tertiary Cortices

Involved in higher-order functions related to reasoning, thought, and language.

Main Inputs to the Cortex

Primarily from the thalamus, terminating at layers 1 through 4.

Main Outputs of the Cortex

Sent through layers 5 and 6, descending through the internal capsule to various subcortical sites.

Thickness of Cerebral Cortices

Ranges from 1.5 to 4.5 mm with a surface area of 2200 cm-sq.