Function of thalamus in human brain

The thalamus is a busy place in the human brain, and a stroke there can have a wide range of effects.

By Jon Caswell

The thalamus is a busy place in the human brain, and a stroke there can have a wide range of effects. Jeremy Schmahmann, professor of neurology at Harvard Medical School, director of the ataxia unit and member of the cognitive behavioral neurology unit at Massachusetts General Hospital, shared more about this type of stroke.

The thalamus, which means "inner chamber" in Greek, is on top of the brainstem near the center of the brain. It has two halves, each about the size of a walnut. "The thalamus is divided into many different areas, which are connected very specifically to different parts of the brain, " Dr. Schmahmann said. "A stroke in one part of the thalamus will not have the same effect as a stroke in another part."

The thalamus has many functions, including:

• It manages our sensitivity to temperature, light and physical touch and controlling the flow of visual, auditory and motor information;
• The thalamus is involved in motivation, attention and wakefulness;
• It’s in charge of our sense of balance and awareness of our arms and legs;
• It controls how we experience pain;
• It’s also involved in aspects of learning, memory, speech and understanding language; and
• Even emotional experiences, expression and our personalities involve the thalamus.

The thalamus can be thought of as a "relay station, " receiving signals from the brain’s outer regions (cerebral cortex), interpreting them, then sending them to other areas of the brain to complete their job.

Though relatively small, the thalamus controls a big part of how our bodies function and respond to the world around us. "The thalamus has dense connections to all the parts of the brain and receives information from all parts of the brain, " Dr. Schmahmann said. Only a small part of the thalamus receives input from the outside world or sends information to the outside world. Mostly the thalamus helps the cortex and other cells deep within the brain to communicate with each other.

"The thing that makes the thalamus quite special is that it’s a relatively small, very concentrated area deep inside the brain, and a small change in the location of the stroke can produce a substantial change in how the stroke affects the survivor, " Dr. Schmahmann said.

For example, a stroke in the thalamus may cause drowsiness, contribute to the development of epilepsy, impact a survivor’s attention span, or a sense of apathy.