The structure and function of the brain

The brain is the most complex biological structure of the human body. Much of how it works is still not understood by neuroscientists and other professionals whose work is dedicated to researching and applying knowledge about the brain.

The lobes of the brain

The cerebral cortex in the brain can be divided down into four different sections known as lobes. These four sections are known as the temporal, occipital, frontal and parietal lobes.

Temporal lobes

The temporal lobes are located in the largest area of the brain, known as the ‘forebrain’. As with the other lobes of the brain, there is one temporal lobe located in each hemisphere (side) of the brain.

The temporal lobes are involved in several key functions including:

• Auditory perception
• Memory
• Speech
• Language comprehension
• Emotional responses
• Visual perception
• Facial recognition

Damage to the temporal lobes can mean that an individual cannot understand language or produce speech. They may also have difficulties in hearing sounds or in perceiving what specific noises are. Finally, damage in this area may also result in aggression, hallucinations, impaired memory formation and anxiety disorders.

Occipital lobes

The occipital lobes are located at the back of the brain, above the cerebellum, and are the main centres for visual processing. The primary visual cortex is located within the occipital lobes and this receives input from the retinas in the eyes enabling us to see things.

The key functions of the occipital lobes include:

• Visual processing
• Colour recognition
• Reading
• Reading comprehension
• Depth perception
• Recognition of object movement

Damage to the occipital lobes usually results in problems with vision, such as an inability to differentiate between colours and distorted visual perception. It can also lead to hallucinations and an inability to identify words.

Frontal lobes

As their name suggests, the frontal lobes are positioned at the front of the brain and are subdivided into the prefrontal cortex and the motor cortex. The prefrontal cortex is believed to be involved in personality expression and the ability to plan cognitive behaviours. The motor cortex controls nerves that enable people to have voluntary control over their muscles (such as deciding when to walk or sit down).

The frontal lobes are the largest of all of the brain’s lobes and are also responsible for:

• Motor functions
• Higher order functions
• Planning
• Reasoning
• Judgment
• Impulse control
• Memory
• Language and speech

Damage to the frontal lobes can result in loss of the ability to use fine motor skills (such as when fastening buttons or tying shoelaces). It can also lead to an inability to read facial expressions and memory problems, both of which are prevalent in individuals who experience dementia.

Parietal lobes

The parietal lobes are located behind the frontal lobes and above the temporal lobes. They are involved in many important functions, one of which is receiving and processing sensory information from all parts of the body. Therefore, for example, these lobes enable individuals to identify objects simply by touching them, without having to look at what they are.

Other important functions include:

• Cognition
• Information processing
• Touch sensation (pain, temperature, etc.)
• Understanding spatial orientation
• Movement coordination
• Speech
• Visual perception
• Reading and writing
• Mathematical calculations

Damage to the parietal lobes causes individuals to have problems with reading, writing and spelling as well as causing difficulties in positioning the mouth correctly for speech.

Other problems include poor hand-eye coordination, the inability to distinguish right from left and a general lack of body awareness.

The cerebellum

The cerebellum is located at the base of the brain and is responsible for the following functions:

• Coordination
• Balance
• Muscle tone
• Body positioning, particularly the ability to stand upright

It relays information between muscles and the area of the brain that is responsible for that particular area of movement.

The cerebellum consists of two hemispheres, which are connected by the vermis, which is a narrow line between the two hemispheres. Like some other structures within the central nervous system, the cerebellum consists of both grey and white matter.