Thalamus

Your thalamus is a structure in the middle of your brain. It’s known as the relay station for incoming motor (movement) and sensory (such as touch and sight) information from your body.

Like a relay or post office, all information must first pass through your thalamus before being routed to its destination in your brain’s cerebral cortex. Here, your brain further processes and interprets the information.

What does the thalamus do?

Your thalamus has many functions, including:

• Relaying sensory information: It takes in information, in the form of nerve signals, from all of your senses except smell. Each sensory function has an area in your thalamus (called a nucleus) that receives and transmits the information.
• Relaying motor (movement) information: Like sensory info, motor pathways all pass through your thalamus.
• Prioritizing attention: Your thalamus helps decide what to focus on among the vast amount of information that it receives.
• Assisting consciousness: Your thalamus plays a role in keeping you awake and alert.
• Assisting thinking and memory: Your thalamus is connected with structures of your limbic system. This system helps process and manage emotions and form and store memories. It also plays a role in learning.

Where is it located?

Your thalamus lies above your brainstem in the middle of your brain. This central location allows nerve fiber connections to reach all areas of your cerebral cortex (the outer layer of your brain).

What does it look like?

You have two thalami, side-by-side, one in each side of your brain. They look like a pair of eggs. Each is about 1 to 1.5 inches (3 to 4 centimeters) long.

What are the parts of the thalamus?

Your thalamus consists of several specialized areas called nuclei. They’re each responsible for processing different sensory or motor impulses from your body. They then send the selected information through nerve fibers to an area of your cerebral cortex.

Some of the nuclei, their function and to what area of your cerebral cortex they send info include:

• Anterior nucleus: It supports memory, emotions and behavior regulation. It’s connected to your hypothalamus and projects to the cingulate gyrus.
• Dorsomedial nucleus: It has a role in emotional behavior and memory, attention, organization, planning and higher cognitive thinking. It projects to your prefrontal cortex and limbic system.
• Ventral posterolateral nucleus: It relays sensory information from your limbs and trunk. It projects to the somatosensory cortex.
• Ventral posteromedial nucleus: It relays sensory information from your head and face and projects to the somatosensory cortex.
• Ventral anterior nucleus, ventral intermediate nucleus and ventrolateral nucleus: They relay movement information. They project to the substantia nigra, premotor cortex, reticular formation and corpus striatum.
• Lateral posterior nucleus: It has thinking functions and determines prominent visual stimuli. It projects to your visual cortex.
• Pulvinar nucleus and lateral geniculate nucleus: They process information you see and project to your visual cortex.
• Medial geniculate nucleus: It processes things you hear. It projects to your auditory cortex.
• Reticular nucleus: It makes up the outer covering of your thalamus. It influences the activity of other nuclei within your thalamus.
• Intralaminar nuclei: These are a group of smaller nuclei that are encircled in a membrane that separates larger thalamic nuclei. One of the most important nuclei in this group is the centromedian nucleus. It has wide projections to the brain surface, particularly to the central motor and sensory regions of the brain. And it has a role in maintaining alertness.

What happens if my thalamus is damaged?

Your thalamus is a central relay station for receiving incoming sensory and motor information. Your thalamus then sends this information to other parts of your brain. So, damage to your thalamus can affect many functions.

The main causes of damage to your thalamus include stroke or tumors in this area of your brain. Some nutritional deficiencies, like vitamin B1 deficiency, can impair thalamic function.

Specific conditions that are affected by or damage your thalamus include:

• Fatal familial insomnia: This is a hereditary condition in which proteins cluster in your thalamus. It causes worsening insomnia, hallucinations and other issues. It eventually leads to death.
• Creutzfeldt-Jacob disease and Fabry disease: These conditions share a feature that helps diagnose them. It’s called the pulvinar sign. A change in density at the back of your thalamus appears in the shape of hockey sticks on an MRI scan.

Signs and symptoms that something isn’t working right

Symptoms of damage to your thalamus include:

• Chronic pain or thalamic pain syndrome (tingling or burning pain)
• Lack of interest or enthusiasm (apathy)
• Loss of ability to understand language or speak (aphasia)
• Memory loss
• Movement issues, like tremors
• Sleepiness or insomnia
• Trouble with attention and a loss of alertness
• Vision problems, including vision loss or light sensitivity

Thalamus damage can also lead to a loss of consciousness or coma.

Is the thalamus a target for any treatment?

Healthcare providers use thalamic stimulation with implantable brain stimulators to treat a variety of conditions, including tremor, Parkinson’s disease and drug-resistant epilepsy.