Frontal Lobe

DESCRIPTION

The frontal lobes are located at the front of the cerebrum. They are the part of the brain that regulates and mediates the higher intellectual functions, known as executive functions. They play an important role in the control of social behaviours.

FUNCTION

The frontal lobes contribute to the regulation of emotions, cognition, error detection, volition, a sense of self, and more. The executive functions of the frontal lobes involve the ability to recognise future consequences resulting from current actions, to choose between good and bad actions, override and suppress unacceptable social responses, and determine similarities and differences between things or events. The frontal lobes also play an important part in retaining longer-term memories, which are often derived from input from the limbic system, or emotional brain. The frontal lobe modifies those emotions to generally fit socially acceptable norms.

RESULT OF INJURY

Damage to the frontal lobes can lead to a wide variety of symptoms, including the loss of inhibitions and impaired mental flexibility. It may be difficult to prioritise tasks, and motivation may diminish. Talking may increase or decrease dramatically. Perceptions about taking risks and following rules can be impaired and socialisation can diminish or increase. Damage to some areas of the frontal lobe can affect sexual interest and habits.

Parietal Lobe

DESCRIPTION

The parietal lobes are positioned above the temporal lobes and between the frontal and occipital lobes. They contain the part of the brain primarily responsible for movement and the sense of touch. They also play a very important role in integrating sensory information, particularly determining spatial sense and navigation.

FUNCTION

The parietal lobes contain the portion of the brain primarily responsible for movement. This area is called the motor cortex. Located next to the motor cortex is the area of the brain primarily responsible for the sense of touch. This area is known as the somatosensory cortex. A large portion of the parietal lobe acts as an interchange for information for most of the other senses. These interconnections contribute a great deal to the ability to interpret people, places, and things around us. In essence, the parietal lobes "pull it all together."

RESULT OF INJURY

Damage to the parietal lobes can result in conditions known as agnosia and apraxia. Agnosia is the inability to recognise an object, using a specific sense, even though that sense is basically intact. For example, someone might not be able to recognise an orange by sight, although they could identify the orange by touch or smell.

Apraxia is the inability to perform a specific movement, although all of the muscles are intact and able to perform that task under different circumstances. For example, someone may be unable to touch their nose on command, but would be perfectly able to do so if their nose itched.

Damage to the parietal lobe can also cause word blindness, known as alexia, with writing impairments, called agraphia. Damage to the right parietal lobe can impair skills such as dressing and washing, and can also cause difficulty in making things, denial of deficits and loss of drawing ability. Damage can also cause a person to neglect the opposite side of their body, even to the point of not recognising their own limbs.

Temporal Lobe

DESCRIPTION

The temporal lobes are the part of the cerebrum that are involved in speech, memory, and hearing. They are located on both sides of the brain, below the parietal lobes and in front of the occipital lobes.

FUNCTION

The temporal lobe is involved in hearing and understanding what is heard, and is home to the primary auditory cortex. It is also responsible for the formation and retrieval of long-term memories. The temporal lobe also plays a role in vision, sexual behaviour, and personality.

RESULT OF INJURY

Individuals with temporal lobe damage have difficulty placing words or pictures into categories. Language skills can also be impaired by temporal lobe damage. The impairment or loss of long-term memory can result from injury to the temporal lobes. Specifically, damage to the right side of the temporal lobes can result in the inability to recall non-verbal material, such as music and drawings. It can also cause a loss of inhibition when talking. Left temporal lobe damage can impair the ability to recognise words and can result in impaired memory for verbal material.

Occipital Lobe

DESCRIPTION

The occipital lobes are located in the back of the brain and are the smallest of the four lobes. They are the visual center, and are the primary portion of the brain responsible for receiving input from the eyes.

FUNCTION

The occipital lobes receive and process all input from the eyes. Area A is the primary visual cortex and the recipient of visual input from the eyes. Area A performs the initial processing of the information, for example combining input from the two eyes, and beginning to analyse depth. This information is then passed on to Areas B and C. Areas B and C are the associative visual cortex, where motion, color, and other parameters are interpreted to provide meaning.

RESULT OF INJURY

Damage to the right occipital lobe can result in loss of the left visual field of both eyes, and damage to the left occipital lobe results in loss of the right visual field of both eyes. Damage to both the left and right occipital lobes can result in blindness, even though the eyes themselves may be functioning normally. This condition is called cortical blindness. If the front part of the occipital lobe is damaged, people have difficulty recognising familiar objects and faces and accurately interpreting what they see.

Septal (Corpus Collosum)

DESCRIPTION

The corpus callosum is a thick band of fibres located between the cerebral hemispheres. It connects the left and right sides of the brain and is the largest fiber bundle in the human brain, with more than 300 million axons.

FUNCTION

The job of the corpus callosum is to channel nerve transmissions between the two hemispheres of the brain. It ensures that each hemisphere has access to data from the opposite side of the body and the surrounding environment.

RESULT OF INJURY

Damage to the front of the corpus callosum can lead to impaired judgment and defective memory, while damage to the rear part can cause behavioural changes.

Hypothalamus

DESCRIPTION

The hypothalamus links the nervous system to the endocrine system, which is primarily responsible for the metabolism. It is located just above the brain stem.

FUNCTION

The main function of the hypothalamus is to maintain the body's status quo. The hypothalamus precisely controls blood pressure, body temperature, fluid and electrolyte levels, and body weight. It also influences hunger, moods, sex drive, circadian cycles, thirst, and the release of hormones from the pituitary gland.

RESULT OF INJURY

Injury to the hypothalamus can result in a wide range of symptoms, including weight loss or gain, depression, aggression, insomnia, loss of sex drive, hypersexuality, and many other conditions. Severe injury to the hypothalamus, such as a shearing injury, may be fatal because it can disrupt the normal homeostasis of blood chemistry, body temperature, and other important functions.

Olfactory System

DESCRIPTION

The olfactory system includes the olfactory epithelium, located inside the nose, the olfactory bulb, which is located just above the olfactory epithelium, and the olfactory cortex, which is on the surface of the temporal lobe. The olfactory system is responsible for the sensing, processing, and identifying of smells.

FUNCTION

The olfactory system is responsible for the sense of smell. In addition, it combines with taste information in the brain to create the sensation of flavour. Many people with a lost sense of smell retain the ability to detect salty, sweet and bitter tastes, but complain that food tastes bland. The sense of smell is strongly associated with memory. As a result, smells are often powerful triggers for specific memories, both good and bad. Because the sense of smell is also closely associated with the limbic system, or emotional brain, smell is known to provoke strong emotional responses.

RESULT OF INJURY

Damage to the olfactory system can cause an impairment or loss of the sense of smell and the sense of taste. Much of what we attribute to our sense of taste actually depends on the aromas of what we eat and drink.

Cerebellum

DESCRIPTION

The word cerebellum means "little brain." The cerebellum is located at the base of the brain and is involved with the coordination of movement. It makes up approximately 10 percent of the brain's volume and contains at least half of the brain's neurons. It is divided into two hemispheres that are covered by a thin layer of grey matter known as the cortex.

FUNCTION

The cerebellum receives input from other areas of the brain and spinal cord, along with information about the position and movement of the body's limbs and joints. It uses all of this information to control equilibrium, and to provide precise coordination of movements.

RESULT OF INJURY

A patient may experience problems with one or more of the following:

• Gait, where the manner of standing or walking is not normal.
• Ataxia, which is unsteadiness or lack of coordination of the limbs, posture, and gait.
• Hypotonia, which is decreased muscle tone.
• Tremor, where parts of the body can tremble uncontrollably, especially with any purposeful movement such as trying to pick up or point at an object.
• Abnormal eye movement, such as impaired tracking, fixation, and an involuntary, constant, twitching of the eye called nystagmus.

Limbic System

DESCRIPTION

The limbic system lies just under the cerebrum within the core of the brain. It is thought to include the hypothalamus, the hippocampus, and the amygdala and other structures. The role of the limbic system is not well understood, however, it plays an important part in regulating emotions and pleasure, and contributes to the formation of memories.

FUNCTION

The limbic system is involved in emotions and motivation, especially those related to survival, including fear and anger. The limbic system is also involved in feelings of pleasure, such as those experienced from eating and sexual activity. The amygdala and hippocampus are key parts of the limbic system that play important roles in memory. The amygdala is responsible for determining what memories are stored and where in the brain those memories are stored.

RESULT OF INJURY

Injury to the limbic system can result in changes in behaviours ranging from subtle to severe. Those changes can include such things as flat affect, which means showing no expression, aggressiveness, mild distractibility, or the inability to pay attention for any length of time. Memory problems can also result from injury to the limbic system, ranging from almost imperceptible challenges with recall, to the inability to remember an event that just happened.

Brain Stem

DESCRIPTION

The brain stem is a part of the brain located beneath the cerebrum and in front of the cerebellum. It connects the spinal cord to the rest of the brain, and is responsible for regulating many of the body's basic functions. It is sometimes referred to as the most primitive portion of the brain.

FUNCTION

Neurological functions located in the brainstem include those necessary for survival, such as breathing, digestion, heart rate, and blood pressure, and for being awake and alert. It plays an important role in basic attention, arousal, and consciousness. One key part of the brain stem is called the reticular activating system, which works as the "on/off switch," in terms of sleeping, waking up, and motivation.

The brain stem serves as a conduit, with information to and from other parts of the body passing through the brain stem on the way to or from the brain.

Many of the cranial nerves originate in or pass through the brain stem. These nerves are responsible for things such as vision, hearing, taste, smell, the control of eye movements, and movement and sensation of the face.

RESULT OF INJURY

The brain stem is vital to proper body functions and can cause severe disabilities if it is damaged. In fact, because the brain stem controls such basic functions as breathing and heartbeat, damage to the brain stem can result in death. Brain stem injury is also a cause for persistent coma. Brain stem injury can also result in memory problems, difficulty concentrating, difficulty staying focused, and physical problems including the inability to walk, remain balanced, and a loss of strength. Problems with vision, such as impaired eye movement can also be caused by injury to the brain stem. Paralysis may also occur when the brain stem is damaged since it is directly linked to the spinal cord.