Cerebral Cortex

What is the cerebral cortex?

Your cerebral cortex is the outermost layer of your brain. Its surface has many folds, giving it a wrinkled appearance. The folds consist of many deep grooves called sulci and raised areas called gyri. These folds add to the surface area of your cerebral cortex, allowing large amounts of information to be processed by more nerve cells. Your cerebral cortex makes up about half of your brain’s total mass.

Your cerebral cortex consists of six layers of nerve cells that contain between 14 billion and 16 billion nerve cells. It’s two millimeters (mm) to four mm (0.08 inches to 0.16 inches) thick.

Your cortex is divided into four lobes: frontal, parietal, temporal and occipital. Each of these lobes is responsible for processing different types of information. Collectively, your cerebral cortex is responsible for the higher-level processes of the human brain, including language, memory, reasoning, thought, learning, decision-making, emotion, intelligence and personality.

Why is the cerebral cortex called gray matter?

The gray matter found in the outer layer of your brain consists of nerve cell bodies, including the end portion of nerves called dendrites. Dendrites are the part of a nerve cell that receives the chemical message from another cell. Your cerebral cortex is gray because that section of the nerve lacks the fatty covering material called myelin.

White matter in your brain is made up of bundles of axons, the long center section of a nerve cell that’s wrapped in myelin. The myelin gives the tissue its whitish color.

What’s the difference between the cerebral cortex and the cerebrum?

Your cerebral cortex is the outer layer that lies on top of your cerebrum. Your cerebrum is the largest area of your brain. Your cerebrum divides your brain into two halves called hemispheres. The hemispheres are attached by a bundle of nerve fibers called the corpus callosum. The corpus callosum allows your two hemispheres to communicate with each other.

What is the neocortex?

Most of your cerebral cortex is considered to be the neocortex. “Neo” means new. Your neocortex is so named because its appearance is thought to be relatively new in vertebrate evolution. In humans, 90% of the cerebral cortex is the neocortex.

What are the functions of the cerebral cortex?

Your cerebral cortex is involved in many high-level functions, such as reasoning, emotion, thought, memory, language and consciousness. Each lobe of your brain is associated with different functions.

Functions of the frontal lobe

Your frontal lobe is at the front of your brain behind your forehead. Functions of your frontal lobe include:

• Decision-making, problem-solving.
• Conscious thought.
• Attention.
• Emotional and behavioral control.
• Speech production.
• Personality.
• Intelligence.
• Body movement.

Special areas of note within this lobe are the motor cortex, the prefrontal cortex and Broca’s area. Your motor cortex is responsible for body movement. Your prefrontal cortex is in charge of “executive functions,” such as thinking and problem-solving. It also supervises and directs other areas of your brain. Broca’s area is a part of your frontal lobe that’s involved with speech production.

Functions of the occipital lobe

Your occipital lobe is at the back of your brain. Functions of your occipital lobe include:

• Visual processing and interpretation.
• Visual data collection regarding color, motion and orientation.
• Object and facial recognition.
• Depth and distance perception.
• Visual world mapping.

Functions of the parietal lobe

Your parietal lobe is located between your frontal and occipital lobes and above your temporal lobe. Functions of your parietal lobe include:

• Sensory information (touch, pressure, pain, position, vibration, temperature) processing.
• Spatial processing and spatial manipulation. This is the ability to understand where you are in three-dimensional space, such as how to navigate around your home or town.

Special areas of note within this lobe are the somatosensory cortex. It receives sensory information (“feeling” information) from all over your body. Here’s an example of how brain lobes work together:

The motor cortex in your brain’s frontal lobe sends the message that directs the muscles in your arm and hand to reach out toward a cup of soup on your kitchen table. The somatosensory cortex of your parietal lobe assesses the information delivered through your touch of the cup, including judgment of its temperature. Spatial processing in your parietal lobe allows you to grasp the cup, flawlessly navigating hand-to-cup distance relative to the table and other surrounding objects.

Functions of the temporal lobe

Your temporal lobe is located between your frontal and occipital lobes and below your parietal lobe. Functions of your temporal lobe include:

• Language comprehension, speech formation, learning.
• Memory.
• Hearing.
• Nonverbal interpretation.
• Sound-to-visual image conversion.

A special area of note within this lobe is Wernicke’s area. This area was more recently discovered to be involved in language comprehensive based on speech tones and sounds, linking them to previously learned sounds.

What are the areas of the cerebral cortex?

Some researchers look at the brain in another way and classify the areas of the cerebral cortex by their three main types of functions: sensory, motor and association areas.

Sensory areas: These areas of your cerebral cortex receive sensory information from your senses and your environment. Functions include:

• Making sense of visual information and object recognition. These functions are processed by an area of your occipital lobe called the visual cortex.
• Assessing touch, temperature, position, vibration, pressure and pain information from your body. These functions are processed by an area of your parietal lobe called the somatosensory cortex.
• Processing hearing information. This function is processed by an area of your temporal lobe called the auditory cortex.
• Processing taste and flavor. These functions are processed by an area of your frontal lobe called the gustatory cortex.

Motor areas: These areas of your cerebral cortex are involved in voluntary muscle movement. These functions are processed mainly by your frontal lobe. Functions include:

• Coordination of muscle movement.
• Planning of complex movements.
• Learning through imitation and empathy.

Association areas: These areas are spread throughout all four lobes and connect and add complexity to functions. Functions include:

• Organizing and giving meaning to information from sensory and motor areas.
• Personality and controlling emotional behaviors.
• Spatial awareness and reasoning.
• Memory processing.
• Think in a visual manner and retain visual memories.
• Build visual information with memories, sound and language.

How might the cerebral cortex be damaged?

Damage to any area of your cerebral cortex typically results from tumors, trauma, autoimmune diseases or a cerebrovascular accident (brain bleed or stroke).

What are the symptoms of a damaged cerebral cortex?

Symptoms depend on the area of the cerebral cortex that’s damaged.

Injury to the frontal lobe

Symptoms of damage or injury to your frontal lobe include:

• Memory issues.
• Personality changes.
• Problem-solving, decision-making issues.
• Attention problems.
• Emotional deficit, socially inappropriate behavior, behavior changes.
• Lack of ability to understand or express speech (aphasia).
• Difficulty speaking (apraxia).
• Weakness, paralysis, loss of muscle control on one side of the body (flaccid hemiplegia).

An additional cause of damage to the frontal lobe is dementia.

Injury to the parietal lobe

Symptoms of damage to your parietal lobe include:

• Memory generation.
• Trouble writing or being unable to write (agraphia).
• Difficulties with math.
• Numbness.
• Disorientation.
• Poor hand-to-eye coordination.
• Inability to identify objects by touch only (astereognosis).
• Loss of sensation.
• Aphasia.
• Apraxia.

Injury to the temporal lobe

Symptoms of damage to your temporal lobe include:

• Hearing difficulties.
• Memory issues.
• Difficulty recognizing faces and objects.
• Language impairments (such as Wernicke’s aphasia), difficulties understanding language.

Additional causes of damage to the temporal lobe include epileptic seizures, developmental dyslexia and Alzheimer’s disease.

Injury to the occipital lobe

Symptoms of damage to your occipital lobe include:

• Difficulty perceiving more than one object at the same time.
• Trouble recognizing objects by sight.
• Color blindness.
• Hallucinations involving vision.
• Total blindness.

A note from Cleveland Clinic

Your cerebral cortex is the outer covering of the surface of your brain. It consists of between 14 billion and 16 billion nerve cells. Your cortex is involved in higher processes in the human brain, including memory, thinking, learning, reasoning, problem-solving, emotions, consciousness and functions related to your senses.