The thalamus is a large, dual lobed mass of gray matter buried under the cerebral cortex. It is involved in sensory perception and regulation of motor functions. The thalamus is a limbic system structure and it connects areas of the cerebral cortex that are involved in sensory perception and movement with other parts of the brain and spinal cord that also have a role in sensation and movement. As a regulator of sensory information, the thalamus also controls sleep and awake states of consciousness. The thalamus sends out signals in the brain to reduce the perception of and response to sensory information, such as sound during sleep.
The thalamus is involved in several functions of the body including:
- Motor Control
- Receives Auditory, Somatosensory, and Visual Sensory Signals
- Relays Sensory Signals to the Cerebral Cortex
- Memory Formation and Emotional Expression
- Pain Perception
- Controls Sleep and Awake States
The thalamus has nerve connections with the cerebral cortex and hippocampus. In addition, connections with the spinal cord allow the thalamus to receive sensory information from the peripheral nervous system and various regions of the body. This information is then sent to the appropriate area of the brain for processing. For example, the thalamus sends touch sensory information to the somatosensory cortex of the parietal lobes. It sends visual information to the visual cortex of the occipital lobes and auditory signals are sent to the auditory cortex of the temporal lobes.
Directionally, the thalamus is situated at the top of the brainstem, between the cerebral cortex and midbrain. It is superior to the hypothalamus.
The thalamus is divided into three sections by the internal medullary lamina. This Y-shaped layer of white matter formed of myelinated fibers divides the thalamus into anterior, medial, and lateral parts.
The thalamus is a component of the diencephalon. The diencephalon is one of two major divisions of the forebrain. It consists of the thalamus, hypothalamus, epithalamus (including the pineal gland), and subthalamus (ventral thalamus). Diencephalon structures form the floor and lateral wall of the third ventricle. The third ventricle is part of a system of linked cavities (cerebral ventricles) in the brain that extend to form the central canal of the spinal cord.
Damage to the thalamus may result in a number of problems related to sensory perception. Thalamic syndrome is condition that causes an individual to experience excessive pain or a loss of sensation in limbs. Damage to areas of the thalamus that are associated with visual sensory processing can cause visual field problems. Damage to the thalamus can also result in sleep disorders, memory problems, and auditory issues.