A deeper understanding of the basal ganglia function will help people better comprehend speech and motion-related diseases and a number of neurological disorders. This particular part of the brain is much involved in facilitating movement, speech as well as in processing emotions. The basal ganglia are composed of several different structures buried deep within the brain which are interconnected to each other to subconsciously aid movement. Brain cell damage and death can make the basal ganglia dysfunctional leading to motion and speech problems as well as motivation issues and impaired memory.
Location and Structure of the Basal Ganglia
Basal ganglia refer to sets of nuclei (in the left and right hemisphere) deep within the central part of the brain which are interconnected with each other. These nuclei perform a very important role in initiating and controlling movement. The basal ganglia consist the of caudate nucleus, putamen and globus pallidus. The caudate nucleus and putamen are both structures of striatum.
- Caudate nucleus
This is a C-shaped gray mass that has a head, body and tail and is involved in processing signals related to motivation and behavior.
Putamen is a rounded gray mass lying next to the head of the caudate nucleus. It is involved in processing motor and sensory signals.
- Globus Pallidus
Globus pallidus is the triangular mass inside the putamen that receives signals coming from the putamen and caudate nucleus. It has internal and external parts. Globus pallidus interna (GPi) has to do with controlling posture, whereas the globus pallidus externa (GPe) is involved in managing and sending signals of motor functions to the thalamus.
The striatum, which is comprised of the putamen and caudate nucleus, is the site for major inflow neural pathway of the basal ganglia, while the globus pallidus is the region for major outflow neural pathway of the basal ganglia. Aside from these nuclei, there are two complementary structures that help the basal ganglia perform their motor functions, and these are the substantia nigra and subthalmic nucleus.
- Substantia nigra
The substantia nigra, which lies beneath the thalamus in the upper part of the midbrain, sends neurotransmitters to help stimulate movement. It comes in two parts, namely the pars compacta which transmits the neurotransmitter dopamine, and the pars reticulata, which transmits neurotransmitter GABA.
- Subthalmic nucleus
This is a lens-shaped structure under the thalamus which acts as a braking system to prevent execution of certain movements that are inappropriate to the situation. The subthalmic nucleus thereby ensures a coordinated voluntary movement.
Basal Ganglia Function
There are still many more to discover about basal ganglia function and experts are continually studying to uncover them. However, early findings do reveal that the set of nuclei that make up the basal ganglia is so much involve in processing motor circuits or signals from different parts of the cortex to the thalamus. They either work directly or indirectly. When the basal ganglia are said to be working directly, they are initiating voluntary movements. When they are operating indirectly, they blocking or braking voluntary movements. The following example will perfectly illustrate this.
Suppose the body is at rest and the motivation to move sparks when a ball is spotted. Motor signals or the information to pick up the ball from the brain and dopamine neurotransmitters from the substantia nigra pars compacta are sent to the striatum. The caudate nucleus and putamen then processes the information and transmit GABA neurotransmitters to the globus pallidus interna to inhibit it. With an inhibited GPi, the appropriate motor signals from the striatum will pass onto the thalamus and continue to the motor cortex resulting in the execution of movement.
However, the if the brain senses danger and figures out that the previous motor signal is inappropriate, the striatum processes the new information and sends it to the subthalmic nucleus. The subthalmic nucleus acts as a two-way braking system by stimulating the substantia nigra pars reticulata and globus pallidus interna to prevent the thalamus from allowing the motor cortex to execute the movement.
Reasons for Basal Ganglia Malfunction
A number of things can disrupt the optimum basal ganglia function, and these include:
- Nerve cell damage and cell death caused by stroke, tumors and infection
- Damaged basal ganglia due to traumatic head injury
- Drug overdose or side effects of medication
Malfunctioning basal ganglia is manifested by movement changes and difficulties, tremors and walking difficulties. Also, those who suffer from the condition may not able to control their movements or repeat certain actions over and over again. Speech and memory could also be affected.
Diseases caused by Malfunctioning Basal Ganglia
Among the problems that may result if the normal basal ganglia function is disrupted or disturb are:
- Parkinson’s Disease
- Cerebral Palsy
- Huntington’s Disease
- Tourette’s Syndrome
The treatment for malfunctioning basal ganglia will help sufferers and their families deal with its effects. It is designed individually and may involve a combination of occupational, physical and speech therapies.