Neocortical

Neocortex

The neocortex is a part of the brain in mammals that is involved in higher-order brain functions such as sensory perception, cognition, generation of motor commands, spatial reasoning, and language. It is the most recent part of the cerebral cortex to evolve and is the largest part of the cerebral cortex in humans.

Structure

The neocortex is a six-layered structure that is part of the cerebral cortex, which also includes the paleocortex and archicortex. The neocortex is distinguished by its layered organization, with each layer having distinct types of neurons and connections.

Layers

The neocortex is organized into six layers, numbered from the outermost layer (Layer I) to the innermost layer (Layer VI):

• Layer I: The molecular layer, which contains few neurons and is primarily composed of dendrites and axons.
• Layer II: The external granular layer, which contains small pyramidal neurons and stellate cells.
• Layer III: The external pyramidal layer, which contains larger pyramidal neurons that project to other cortical areas.
• Layer IV: The internal granular layer, which receives input from the thalamus and is prominent in sensory areas.
• Layer V: The internal pyramidal layer, which contains large pyramidal neurons that project to subcortical structures.
• Layer VI: The multiform layer, which contains neurons that project to the thalamus and other cortical areas.

Columns

The neocortex is also organized into vertical columns, known as cortical columns, which are thought to be the basic functional units of the neocortex. Each column is a cylindrical structure that spans all six layers and processes a specific type of information.

Function

The neocortex is involved in a wide range of functions, including:

• Sensory perception: The neocortex processes sensory information from the thalamus and integrates it to form perceptions.
• Motor control: The neocortex generates motor commands that are sent to the spinal cord and other parts of the brain to control movement.
• Cognition: The neocortex is involved in higher cognitive functions such as reasoning, problem-solving, and decision-making.
• Language: The neocortex is critical for language processing, including both comprehension and production.

Development

The neocortex develops from the embryonic telencephalon, which is part of the forebrain. During development, the neocortex undergoes a process of radial migration, where neurons migrate from the ventricular zone to their final positions in the cortical layers.

Evolution

The neocortex is a relatively recent evolutionary development, appearing first in mammals. It is thought to have evolved from the dorsal pallium of early vertebrates. The expansion of the neocortex is particularly pronounced in primates, and especially in humans, where it accounts for a large proportion of the brain's volume.

Clinical Significance

Disorders of the neocortex can lead to a variety of neurological and psychiatric conditions, including:

• Epilepsy: Abnormal electrical activity in the neocortex can lead to seizures.
• Autism spectrum disorders: Abnormalities in neocortical development and connectivity are thought to contribute to autism.
• Schizophrenia: Changes in neocortical structure and function are associated with schizophrenia.
• Alzheimer's disease: Degeneration of the neocortex is a hallmark of Alzheimer's disease.

Also see

• Cerebral cortex
• Thalamus
• Pyramidal neuron
• Cortical column
• Neuroplasticity