The thalamus  is a midline symmetrical structure of two halves, within the vertebrate brain, situated between the cerebral cortex and the midbrain. Some of its functions are the relaying of sensory and motor signals to the cerebral cortex, and the regulation of consciousness, sleep, and alertness. The medial surface of the two halves constitute the upper lateral wall of the third ventricle. It is the main product of the embryonic diencephalon.

The function of the thalamus is to regulate the body’s voluntary motor control, consciousness and its sleep/wake cycle. It also regulates the senses of sight, sound, taste, touch and the sense of where the person’s body is in space. The thalamus decides which signals from the ears, eyes, mouth and skin to relay to its area in the cerebral cortex. The thalamus doesn’t relay information about the sense of smell.

The thalamus may also be involved in the regulation of some types of memory. The thalamus and the cerebral cortex operate in a feedback loop, especially when it comes to the sleep/wake cycle. The thalamus not only sends signals to the cortex, but the cortex in turn sends signals back to the thalamus. Damage to this system can put a person at risk for irreversible coma.

An inherited condition causes the thalamus to degrade over time, leading to insomnia that can prove fatal. A stroke that affects the thalamus can lead to a disorder where the patient feels pain or burning on one side of the body, accompanied by changes in mood.

The thalamus is divided into two walnut-sized parts. Both are found in deep in the center of the brain, between the midbrain and the cerebral cortex.

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