Cerebral Cortex: Higher Mental Functions

Neuroscience

Uniqueness of the brain in its ability to serve higher mental functions:

Reasoning, memory, language, speech, calculations, praxis, objects recognition.

Cerebral cortex

Functions are asymmetrically organized in the cerebral hemispheres.

Cerebral dominance i.e. specialization of one hemisphere in specific functions relates to unique cytoarchitectural organization.

Cerebral cortex 

I = molecular layer (most superficial)

II = external granular layer

III = external pyramidal layer (contains pyramidal neurons to which you have axons that project to other parts of the brain) (one of the major sources of the cortical connections.) (These cells are important for communication- sending messages to other parts of the brain)

IV = internal granular layer (sensory information)

V = internal pyramidal layer (pyramidal = motor) (the largest pyramidal neurons in the brain, send long projections to subcortical areas and brainstem all the way down to the spinal cord) (major output for the pyramidal system). 

VI = multiform layer (helps with the regulating and fine-tuning of information). (making sense of feedback) 

Morphology of the brain

Reflects many different functions of the brain.

The structure and the form of the brain.

Morphology drives function.

Cytoarchitecture

Different layers of the human brain, levels of tissue.

Cortex is not a uniform sheet 

neurons that will contribute to different processing. (tasting and touching neurons will be different.

Pyramidal cells

Most common type of neurons.

They are large and have a triangular shape.

At the end they have dendrites.

They serve as primary output neurons of the brain.

Send long projections to other cortical areas as well as the brain stem and spinal cord.

Essential for motor control, cognition, and communication between different regions of the brain.

Fusiform Cells

Spindle shape

Located in the deep cortical layers

Send info back to the thalamus and provide feedback information or loop.

Help to regulate sensory input.

Stellate cells

They have a star shape

Find them in the internal granular layer

Their job is to serve as connectors, interneurons

They receive incoming sensory information and is important to the thalamic input.

Provide feedback to thalamus and thalamus distributes that information

Horizontal cells of  Cajal-Retzius

Cells that are found as you go to the surface 

Mostly in the surface of the cortex

Play a critical role during the development of the human brain

Guide in the development in the formation of the cortex. 

Major function is in the development 

Cells of Martinotti

Small and interneurons

Found in the upper area of level I

They provide inhibitory control of the system.

Problem with these cells = people lose their inhibition

Molecular layer (plexiform)

Superficial layer

located under the pia mater

very few of the neurons

rich in horizontally shaped dentrite branches

Motor cortex

Three areas = primary motor cortex, secondary motor cortex (supplementary and premotor)

region of the cortex itself that is responsible for planning, controlling, and executing voluntary motor movement. 

Do not think of it as a single structure, but a broad network of cells, interconnected areas. 

Each area contributes to a specific element of motor behavior. 

Primary motor cortex

represented in a cortical zone

different from other parts

Secondary motor cortex

prefrontal, frontal, goes around to the parietal area.