Thalamus Function

The brain is a complex organ that acts as the control center of the body. The main divisions of the brain include the forebrain, midbrain, and hindbrain. The forebrain is further divided into 2 subdivisions: telencephalon and diencephalon. The diencephalon includes the thalamus, hypothalamus, and pineal gland. Thalamus is a paired structure located in the forebrain which performs several functions. Thalamus's function is to act as a relay center between the subcortical areas and the cerebral cortex.

What is Thalamus?

The thalamus may be a small structure within the brain located just above the brainstem between the cerebral mantle and therefore the midbrain has extensive nerve connections to both. The main and primary function of the thalamus is to relay motor and sensory signals to the cerebral mantle. It also aids in the regulation of sleep, alertness, and wakefulness.

The brain consists of the ventricles or fluid-filled spaces. The thalamus surrounds the third ventricle. It is a subdivision of a part of the brain called the diencephalon and is one of the most important structures derived from the diencephalon during embryonic development.

The thalamus lies at the highest part of the brain stem near the middle of the brain, from where the nerve fibers project out towards the cerebral mantle. The thalamus is split into two prominent bulb-shaped masses of around 5.7 cm long and positioned symmetrically on all sides of the ventricle.

Thalamus Structure

The thalamus is a paired structure of gray matter that is located in the forebrain and is superior to the midbrain. It is also near the center of the brain, where the nerve fibers project out to the cerebral cortex in all directions. The medial surface of the thalamus constitutes the upper part of the lateral wall of the third ventricle and is connected to the surface that is corresponding to the opposite thalamus by a flattened gray band, the interthalamic adhesion. 

The lateral part of the thalamus consists of the pulvinar, the lateral nuclei, and the medial and lateral geniculate nuclei. These are the newest part of the thalamus phylogenetically. There are areas of substantia alba within the thalamus including the stratum zonale that covers the dorsal surface, and therefore the external and internal medullary lamina. The external lamina covers the lateral surface and the internal lamina helps to divide the nuclei into anterior, medial, and lateral groups.

The thalamus is furnished with blood by four branches of the posterior arteria cerebri, namely the polar artery, paramedian thalamic-subthalamic arteries, thalamogeniculate arteries, and therefore the posterior choroidal arteries.

Anatomy

The topography or position of the thalamus, as well as its structure and nucleus, input and output fibres, and blood supply.

Location

The diencephalon includes the thalamus. It is found immediately above the midbrain, deep in the forebrain. On each side of the third ventricle, there is the thalamus. Its anterior section creates the interventricular foramen's posterior boundary.

The pulvinar structure is formed when the posterior end of the brain is extended. The superior colliculus is overshadowed by the thalamic pulvinar. The thalamus' inferior surface connects to the tegmentum of the midbrain.

What is the Function of the Thalamus?

The thalamus performs multiple functions, generally, they are believed to act as a relay station, or hub, and act as relaying information between different subcortical areas and the cerebral cortex. Every sensory system particularly includes a thalamic nucleus that receives sensory signals and sends them to the associated primary cortical area.

For example, in the sensory system, the inputs are from the retina that is sent to the lateral geniculate nucleus of the thalamus, which successively projects to the visual area within the lobe. The thalamus is believed to process both the sensory information as well as a relay of each of the primary sensory relay areas that receive strong feedback connections from the cerebral cortex. Similarly, the medial geniculate nucleus acts as a key auditory relay between the center of the midbrain and therefore the primary auditory area. The ventral posterior nucleus may be a key somatosensory relay, which sends touch and proprioceptive information to the first somatosensory cortex.

The function of thalamus in the human brain is it plays a crucial role in regulating states of sleep and wakefulness. Thalamic nuclei have strong reciprocal connections with the cerebral mantle that help in the formation of thalamo-cortico thalamic circuits that are believed to be involved in consciousness. The thalamus plays a serious role in regulating arousal, the extent of awareness, and activity. Damage to the thalamus in humans can lead to a permanent coma.

The thalamus is a part of the limbic system, which is the area of the brain that is mostly responsible for emotions and memory.

The thalamus is one of several pieces of equipment that work together to filter sensory data into a more understandable and manageable format for higher brain areas. The thalamus and the cerebral cortex have a close association, with several reciprocal connections. The thalamocortical loop is made up of these connections. Arousal processes are modulated, alertness is maintained, and attention is directed to sensory stimuli via the thalamus.

The thalamus is divided into five key functional components, including reticular and intralaminar nuclei, which regulate arousal and pain. The reticular formation is always making educated assumptions about which sensory object is causing these activation patterns. These pattern guesses are compared to similar patterns in memory by the intralaminar circuit. All of these circuits work together to create a unified framework for interpretation.

The thalamus is one of several pieces of equipment that work together to filter sensory data into a more understandable and manageable format for higher brain areas. The thalamus and the cerebral cortex have a close association, with several reciprocal connections. The thalamocortical loop is made up of these connections. Arousal processes are modulated, alertness is maintained, and attention is directed to sensory stimuli via the thalamus.

Sensory nuclei regulate all sensory domains except olfaction, while motor language function is governed by effector nuclei.

Cognitive functions are represented by associative nuclei.

Limbic nuclei are limbic nuclei that comprise emotion and motivation.

The nuclei are in charge of monitoring the cerebral cortex for active brain regions (those firing at roughly 40Hz) and sending this information to the remainder of the thalamus.

Thalamus and Injury 

The thalamus is involved in a wide range of important tasks. The consequences of thalamus injury differ from one person to the next.

• The following are some of the most common thalamic injuries adverse effects:

• Tingling, numbness, hypersensitivity, and pain are examples of sensory disorders.

• Light sensitivity or vision loss

• Impaired motor skills

• Tremors

• Attention deficits

• Loss of memory

• Insomnia

A coma can develop from significant injury to the thalamus, which controls sleep and arousal.

Physiology

Between the cortex and the spinal cord, as well as other parts of the lower brain, the thalamus occupies a key location. As a result, it serves as a crucial relay point for messages travelling from the brain's lower to higher levels. Before reaching the brain's higher regions, almost all sensory information passes through the thalamus.

Thalamus not only relays or passes sensory information to the brain, but it also integrates it. This merged sensory data is subsequently transferred to other parts of the brain. The salivary response is triggered when the smell and taste sensations are combined in this way.

The thalamus controls a person's emotional tone as part of the mammillothalamic tract.

The auditory and visual channels are served by the medial and lateral geniculate bodies, respectively. As a result, it is necessary for a person's normal hearing and visual processes. Its illness will damage both hearing and vision.

The intralaminar nuclei of the thalamus regulate the level of consciousness. The activity of other thalamic nuclei is controlled by these nuclei, which receive information from the reticular formation. As a result, these nuclei regulate the total activity of the cortex, determining a person's level of consciousness and alertness.

The basal nuclei circuit of voluntary movement control includes the ventral anterior and ventral lateral nuclei of the thalamus. They provide information to the motor cortex after receiving information from the globus pallidus. They are necessary for motor function and cognitive control.

The illness of the thalamus, which is a major relay and integrative area. This area of the CNS will have a significant impact on the body. Neoplasia, illness of the vascular supply, or haemorrhage can all cause harm to the thalamus.

The following are some of the most important clinical implications of the thalamus.

The ventral posteromedial and ventral posterolateral nuclei of the thalamus can be damaged by thalamic lesions caused by hemorrhage or thrombosis of arteries. This, in turn, can result in total sensory loss.

Light touch, tactile sensations, discomfort, discrimination, and joint and muscle feelings from the opposite side of the body are all lost.