Get a Description and Diagram of Thalamus Gray Matter

Thalamus
The thalamus (red) processes sensory input and relays it to higher parts of the brain.

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Thalamus Description

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.

Key Takeaways

  • The thalamus, which is dual lobed and composed of gray matter, is involved in the regulation of motor functions in the body and in sensory perception.
  • The thalamus is located at the top of the brainstem. It sits between the cerebral cortex and the midbrain.
  • The thalamus is divided into three main divisions or sections: the anterior, medial, and lateral parts.
  • Injury or damage to the thalamus can produce a host of sensory perception problems.

Thalamus Function

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.

Thalamus Location

Directionally, the thalamus is situated at the top of the brainstem, between the cerebral cortex and midbrain. It is superior to the hypothalamus.

Thalamus Divisions

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.

Diencephalon

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.

Thalamus Damage

Damage to the thalamus may result in a number of problems related to sensory perception. Strokes are caused when there is a problem or issue with the blood flowing to the brain. In a thalamic stroke, the blood flow to the thalamus has an issue that can result in the impaired function of the thalamus. Thalamic syndrome is one such condition that causes an individual to experience excessive pain or a loss of sensation in limbs. Even though these sensations may subside after the initial stroke, the damage caused may lead to other syndromes.

Hematomas in the thalamus may result in headache, vomiting, vision problems and some general confusion. Damage to areas of the thalamus that are associated with visual sensory processing can also cause visual field problems. Damage to the thalamus can also result in sleep disorders, memory problems, and auditory issues.

Other Related Brain Components

  • Hypothalamus Activity and Hormone Production - while the hypothalamus is only about the size of a pearl, it 'directs' a number of important body functions.
  • Epithalamus and Subthalamus - Both the epithalamus and the subthalamus are part of the diencephalon. While the epithalamus aids with our sense of smell and the regulation of sleep and wake cycles, the subthalamus is involved in motor control and movement.
  • Anatomy of the Brain - The anatomy of the brain is very complex since it is the body's control center.

Sources

  • Reece, Jane B., and Neil A. Campbell. Campbell Biology. Benjamin Cummings, 2011.