Basal Ganglia – MemoryFAQs.com

The basal ganglia (or basal nuclei) are a neural network in the brain responsible for movement, perception, and judgment. They consist of a number of large grey mass structures of the cerebral cortex.

Because of their appearance, the basal ganglia are also called “islands” of gray matter, located deep in the cerebrum. These groups of neurons and the cerebral cortex are composed chiefly of the cell bodies and projections (dendrites) of neurons, responsible for the interactions between the cognitive and motor processes.

What Does Basal Ganglia Mean?

The word basal denotes that the basal ganglia are located near the base, or at the bottom of the brain, while the word ganglion is used to describe a cluster of neurons. However, the word is typically used to refer only to neurons in the peripheral nervous system (i.e. outside the brain and spinal cord).

Moreover, the word nucleus is generally used to describe clusters of neurons that are located in the central nervous system. Thus, the basal ganglia could also be referred to as nuclei.

The basal ganglia are one of the most important and fundamental processing units of the brain, responsible for a broad spectrum of functions, including the control of voluntary motor movements, procedural and habit learning, movements of the eyes, cognition, as well as emotion.

Where Are the Basal Ganglia Located?

The basal ganglia are part of a neuronal system that includes the thalamus, the cerebellum, and the frontal lobes.

More precisely, these large structures in the cerebral cortex consist of several interconnected nuclei that are located within:

Telencephalon (the most highly developed and back part of the forebrain)
Mesencephalon (the small central part of the brainstem, midbrain), and
Diencephalon (back part of the brain, containing the epithalamus, thalamus, hypothalamus, ventral thalamus, and the third ventricle).

Anatomy and Structure of the Basal Ganglia

Basal ganglia consist of the following components, i.e grey nuclei:

Striatum, consisting of:

- - dorsal striatum (consisting of the following clusters of neurons: caudate nucleus and putamen in the cerebrum)
  - ventral striatum (consisting of the following clusters of neurons: nucleus accumbens and olfactory tubercle in the cerebrum)
  - Globus pallidus (clusters of neurons located in the cerebrum)

Ventral pallidum – (a specific basal ganglia structure)
Substantia nigra pars reticulata (a gray nuclei located within the midbrain)
Subthalamic nucleus (a gray nuclei in the diencephalon)
Amygdaloid nuclear complex (or Amygdala, part of the limbic system)

Striatum

The striatum is the largest nucleus, i.e. cluster of neurons in the basal ganglia, which consists of:

Dorsal striatum consists of the following clusters of neurons in the cerebrum:
- Caudate nucleus – A cluster of neurons that directly contributes to decision-making, action selection, and initiation. It also plays a vital role in how the brain learns, especially when it comes to storing and processing memories. By using information from past experiences, the caudate nucleus regulates and controls future actions and decisions. This is important for the development and use of language.
- Putamen – A large structure in the outermost part of the brain that plans and aids the movement of the extremities. This group of nuclei is interconnected with the cerebral cortex, the thalamus, and the brainstem.

Ventral striatum – The ventral striatum plays a big role in decision making and reward-related behavior. The ventral striatum is composed of the following clusters of neurons in the cerebrum:
- Nucleus accumbens – A cluster of neurons involved in the cognitive processing of motor function related to the analysis and processing of rewards and reinforcing stimuli. The nucleus accumbens cluster is also responsible for the regulation of slow-wave sleep.
- Olfactory tubercle – A layer of gray matter located in the frontal lobe of the brain that transmits the sensory information from the olfactory receptors (i.e. receptors of smell) to the thalamus, ventral pallidum, and nucleus accumbens in the central nervous system of the brain.

Globus pallidus

Globus pallidus (Lat. a pale body) is a part of the basal ganglia and has a distinct pale appearance due to the large number of myelinated axons it contains. It is responsible for the control and regulation of voluntary movement.

This structure of the basal ganglia is located under the cerebral cortex, next to the putamen. It is one of the main output nuclei of the basal ganglia. From the globus pallidus, neurons form a pathway that can influence neurons in the motor cortex. In this way, they inform the parts of the brain responsible for initiating movements.

Ventral pallidum

The ventral pallidum is a structure of the basal ganglia of the brain. Being one of the major output for the transmission of limbic signals to the nuclei of the thalamus, it is also one of the main reward mechanisms in the brain, as well as a center for the regulation and control of motor functions.

Substantia nigra pars reticulata

The substantia nigra pars reticulata (Lat. black substance) is the largest structure of the basal ganglia and it’s located in the midbrain.

Composed of pars compacta (SNpc) and the pars reticulata (SNpr), the substantia nigra pars reticulata plays an important role in the reward and movement systems of the brain.

Subthalamic nucleus

The subthalamic nucleus is a cluster of neurons in the structure of the basal ganglia. It’s located right below the thalamus, and above the midbrain’s substantia nigra. It produces the neurotransmitter called glutamate, and transmits the sensory information to the globus pallidus.

Amygdaloid nuclear complex (or Amygdala)

The amygdaloid nuclear complex (or Amygdala) comprises a group of more than 10 nuclei that are located in the mid temporal lobe. It is a center in the brain for the control and regulation of the signals and information received from our senses and our internal organs.

The amygdala is responsible for our emotional response, as well as our other reactions to different stimuli.

What Is the Main Function of the Basal Ganglia?

The main function of the basal ganglia is to receive information from the cortex related to voluntary motor movements, procedural learning, habit learning, eye movements, cognitive processes, as well as emotions.

Furthermore, that information is transferred to the motor centers, which, in turn, send it to the parts of the cerebral cortex which are responsible for the control, planning, and regulation of the voluntary motor movements of our body.

Which Medical Conditions and Disorders Can Occur if There Is Damage to the Basal Ganglia?

Even though motor disorders are most often associated with the dysfunction of the basal ganglia, damage to this part of the brain can lead to other severe medical conditions and dysfunctions, such as:

Obsessive-compulsive disorder (OCD) – the basal ganglia are part of the brain commonly associated with OCD – a mental disorder in which the individuals conduct unwanted behaviors in order to get rid of their obsessive ideas, thoughts, feelings, or sensations.
Tourette syndrome – A neurological disorder characterized by the inability of the individual to control simple motor movements (like the movement of the hands, or jerking of shoulder muscles).

The most common symptoms are involuntary tics and vocalizations of profanities, eye blinking, grunting, uttering complex and loud sounds, phrases out of context, etc.

Parkinson’s disease – A neurological disorder that affects the part of the brain that controls the movement of our body. It’s characterized by tremors, rigid muscles, difficulty making quick and smooth movements, as well as difficulty in standing and walking.

Depression – A mood disorder that affects the way an individual feels, perceives events and surroundings and affects their manner of thinking and behaving. This can lead to behavior with negative consequences.

Attention-deficit disorder (ADD) – A neurological disorder characterized by a wide range of behavior problems, such as difficulty in following instructions, focusing on performing a task, an inability to complete a task, being disorganized and forgetful, difficulty in staying on topic while talking, etc.

Lethargy – A pathological state of tiredness and fatigue, characterized by a severe lack of energy, motivation, apathy, and enthusiasm. Unlike the majority of neural diseases and conditions, lethargy can be resolved with plenty of rest and sleep, exercising, and proper nutrition.

Huntington’s Disease – A fatal genetic disorder that worsens an individual’s physical and mental abilities. It’s characterized by a loss of memory, a feeling of hopelessness, a lack of interest in things and events, and problems with memory and movement. By gradually breaking down the nerve cells of the brain, it leads to the loss of language, thinking, and reasoning abilities of the affected individual.

To Sum Up

Each day we perform countless movements by walking, reaching for objects, writing, and so on. The basal ganglia are the main center of the human brain for monitoring, coordinating, and regulating voluntary motor movements, as well as some cognitive skills and emotions.

The basal ganglia are a collection of structures in the cortex of the brain, consisting of the striatum, globus pallidus, ventral pallidum, substantia nigra pars reticulata, subthalamic nucleus, and the amygdaloid nuclear complex.

Damage to the basal ganglia cells can lead to severe medical conditions that affect the voluntary motor and cognitive abilities of the individual.

Fun Facts

Did you know?

The caudate nucleus of the basal ganglia functions as a feedback processor. Namely, it uses our memories from previous experiences in order to influence our future actions and reactions.
The nucleus accumbens cluster of neurons is responsible for the addictive behavior of an individual, because all drugs increase the production of dopamine in the nucleus accumbens, while reducing the production of serotonin.
Dopamine is called the ‘hormone of happiness’, because it’s responsible for our experience of happiness. It is produced in several areas of the brain, including the substantia nigra and the ventral tegmental area, during a pleasurable experience. It is also responsible for our mental and emotional responses, as well as for the motor reactions of our body.
Damage to the basal ganglia can cause various problems and loss of abilities of the affected individual, such as difficulty in controlling speech, maintaining body posture, starting, stopping, or sustaining movements, etc.
The volume of the basal ganglia can be increased through cardiovascular exercises, which have the ability to improve its function.
Unlike animals that walk on all four legs, humans walk on two legs thanks to the functions regulated in the basal ganglia.
During tense and uncomfortable moments, the basal ganglia receive the signal that something’s not quite right with the physical or emotional situation we are in. Thus, they inform the corresponding center of the brain to correct the situation by responding in the right way. For instance, when we are alone at home at night, the basal ganglia alert us to lock the doors.
If the caudate is not sending enough stimulation and information to the centers of the brain associated with motivation, we can lose our motivation to be productive.
The putamen regulates our automated learning, which we use in activities such as riding a bike, driving a car, as well as all other repetitive actions which do not require upper-level thinking.
Even though this part of the brain is smaller than a human’s thumb, the basal ganglia perform an immense range of vitally important every-day functions.