Basal Ganglia

What are the basal ganglia?

The basal ganglia (pronounced “bay-sal” “gang-lee-uh”) are a group of structures near the center of your brain that form important connections. These connections allow different areas of your brain to work together. The basal ganglia manage the signals your brain sends that help you move your muscles.

What do the basal ganglia do?

The basal ganglia are best known for how they help your brain control your body’s movements. However, ongoing research continues to uncover other ways that the basal ganglia interact with other parts of your brain. Though experts continue to uncover more about the inner workings of the basal ganglia, there’s much about them that remains unknown.

Movement

The basal ganglia are a key part of the network of brain cells and nerves that control your body’s voluntary movements. They can approve or reject movement signals that your brain sends, filtering out unnecessary or incorrect signals. This lets you control certain muscles without also using other muscles that are nearby.

If the basal ganglia approve a signal, it continues to the motor pathways, the nerves that eventually carry the signal down your spinal cord and nerves to their destination muscle. If they don’t approve the signal, they redirect it into an area where other brain cells dampen those signals until they stop.

The parts of your brain that process information from your senses, namely sight, sound, smell, taste and touch, also send that information to your basal ganglia. That sensory information helps the basal ganglia refine your movements further.

Decision-making

Another job of the basal ganglia is processing how you evaluate goals and risks. It also processes signals that affect your emotions and your motivation. That means it also plays a role in learning and forming habits, planning and carrying out tasks, and more.

Reward and addiction

Because the basal ganglia involve processes like emotions, motivation and habits, they also affect how you learn and how you feel in response to things happening around you. That includes feeling good (reward) about something you do, or feeling the need to avoid something. Because of the involvement of your brain’s processes with rewards, habits and motivation, the basal ganglia also have a role in illnesses like addiction.

Where are the basal ganglia located?

The basal ganglia aren’t a single structure in your brain. Instead, they include several structures, ganglia and nuclei alike, found at the center of your brain.

The parts of the basal ganglia include:

• Caudate nucleus.
• Globus pallidus.
• Putamen.
• Substantia nigra pars reticulata.
• Subthalamic nucleus.
• Ventral pallidum.

How they connect and work together

The basal ganglia are separate structures that link up in various ways. One way to think of the basal ganglia is like a circuit board found in an electronic device. The ganglia form connections and circuits with different parts of your brain, allowing them to send signals back and forth. Some parts of the basal ganglia can also relay signals from different areas.

There are also different kinds of connections that happen throughout the basal ganglia. Some of these connections are “excitatory,” meaning they cause something to happen. Others are “inhibitory,” meaning they stop signals from continuing. Some connections trigger the release of other neurotransmitter chemicals, which your body uses for communication and activating or deactivating certain processes and systems.

How big is it?

The basal ganglia take up about 10 cubic centimeters of space, which is a volume that’s about the same as a standard gumball.

What is it made of?

The basal ganglia aren’t actually all ganglia. Some of the structures are nuclei, but experts still group them under the name. The definition of nuclei and ganglia are as follows:

• Nuclei: This is the plural term for “nucleus.” Nuclei in your nervous system are nerves or clusters of brain cells with the same job or connecting to the same places.
• Ganglia: This is a plural term for “ganglion.” Ganglia are groups of nerves or brain cells that are closely related. They might share connections and jobs or work together as part of a bigger subsystem of your nervous system.

Making up the nuclei and ganglia are the following:

• Neurons: These cells make up your brain and nerves, transmitting and relaying signals. They can also convert signals into either chemical or electrical forms.
• Glial cells: These are support cells in your nervous system. While they don’t transmit or relay nervous system signals, they help the neurons that do.

Neurons

Neurons are the cells that send and relay signals through your nervous system, using both electrical and chemical signals. Each neuron consists of the following:

• Cell body: This is the main part of the cell.
• Axon: This is a long, arm-like part that extends outward from the cell body. At the end of the axon are several finger-like extensions where the electrical signal in the neuron becomes a chemical signal. These extensions, known as synapses, lead to nearby nerve cells.
• Dendrites: These are small branch-like extensions (their name comes from a Latin word that means “tree-like”) on the cell body. Dendrites are the receiving point for chemical signals from the synapses of other nearby neurons.
• Myelin: This is a thin fatty layer that surrounds the axon of many neurons. It acts as a protective covering and helps speed up certain signals.

Neuron connections are incredibly complex, and the dendrites on a single neuron may connect to thousands of other synapses. Some neurons are longer or shorter, depending on their location in your body and what they do.

Glial cells

Glial (pronounced “glee-uhl”) cells have many different purposes, helping develop and maintain neurons when you’re young, and managing how the neurons work throughout your entire life. They also protect your nervous system from infections, control the chemical balance in your nervous system and create the myelin coating on the neurons’ axons. Your nervous system has 10 times more glial cells than neurons.

What are the common conditions and disorders that affect the basal ganglia?

Conditions that affect the basal ganglia include, but aren’t limited to:

• Addictions.
• Alzheimer’s disease.
• Attention-deficit hyperactivity disorder.
• Brain tumors (including cancer).
• Carbon monoxide poisoning.
• Concussions and other traumatic brain injuries.
• Heavy metal poisoning or other toxins.
• Infections (including those that cause encephalitis).
• Huntington’s disease.
• Lewy body dementia.
• Multiple sclerosis.
• Multiple system atrophy.
• Parkinson’s disease.
• Progressive supranuclear palsy.
• Stroke.
• Tourette syndrome.
• Wilson’s disease.

Common signs or symptoms of problems affecting the basal ganglia?

The symptoms that can happen with conditions that affect the basal ganglia depend strongly on the type of condition. Movement disorders like Parkinson’s disease or Huntington’s disease will have different effects from carbon monoxide poisoning or heavy metal poisoning.

• Balance and coordination problems.
• Muscle weakness and spasms.
• Shakiness and tremors.
• Vision problems.
• Slurred speech.

Common tests to check the health of the basal ganglia?

Several types of diagnostic tests are possible with conditions that affect the basal ganglia. Some of the most common tests include, but aren’t limited to:

• Blood tests (these can detect many problems, ranging from immune system problems to toxins and poisons, especially metals like copper, mercury or lead).
• Computerized tomography (CT) scan.
• Electroencephalogram (EEG).
• Electromyogram (nerve conduction test).
• Evoked potentials (sensory tests).
• Genetic testing.
• Magnetic resonance imaging (MRI).
• Positron emission tomography (PET) scan.

What are some common treatments for conditions that affect the basal ganglia?

The treatments for conditions that affect your basal ganglia can vary depending on the condition in question. There’s no one-treatment-fits-all approach to conditions that affect your brain, and treatments that help one condition can make others worse. Some conditions are treatable with medication only, while others require surgery or other treatments. In some cases, the condition isn’t treatable, so healthcare providers will focus on treating the symptoms.

How can I prevent problems with my basal ganglia?

Many — but not all — conditions that affect the basal ganglia are preventable. Protecting the basal ganglia is very similar to taking care of your entire brain, as well as your body overall. Some of the most important things you can do include:

• Eat a balanced diet. Vitamin levels that are too high or too low can cause problems with your brain or nervous system. Your diet also affects your circulatory health, which can impact your brain (stroke is an example of a condition that happens because of heart and circulatory disorders).
• Stay physically active and maintain a healthy weight. Your weight and activity level can prevent or delay conditions that affect your brain, especially circulatory problems like high blood pressure.
• Wear safety equipment as needed. Head injuries, especially concussions and traumatic brain injuries, can damage the basal ganglia and other parts of your brain. In some cases, that damage is severe and/or permanent. Wearing safety equipment to prevent those injuries is essential, regardless of whether you use that equipment while at work or play.
• Manage your chronic conditions. Many of the conditions that affect your brain and nervous system worsen over time. However, treating those conditions can sometimes stop them or delay how long it takes for them to worsen.

A note from Cleveland Clinic

The basal ganglia have a critical job in your brain, and experts are working to understand even more about what they do. While there’s still a lot that experts don’t yet understand, advances in medical knowledge and technology are helping change that. As understanding of the basal ganglia grows, healthcare providers will have even more ways to diagnose and treat the conditions that affect them.