A small structure of the brain which is located just above the brainstem between the cerebral cortex and the midbrain is called thalamus. Plural form of thalamus is thalami. They have extensive nerve connections to both the cerebral cortex and midbrain. Its main function is to relay motor and sensory signals to the cerebral cortex, along with that it also regulates sleep, alertness, emotion, memory and wakefulness. As thalamus translates neural impulses from various receptors to the cerebral cortex.
About Location of Thalamus
The human brain consists of ventricles or fluid-filled spaces and here thalamus surrounds the third ventricle of the brain. As it is a subdivision of the human brain called as diencephalon and also considered as largest structure diencephalon division during embryonic development.
Anatomy of Thalamus
It is a paired structure made up of gray matter located inside the forebrain which is present superior to the midbrain, close to the center part of the brain, having nerve fibers projecting out to the cerebral cortex in all directions. The surface part of thalamus is made up of the upper part of the lateral wall of the third ventricle along with that it is connected to the corresponding surface of the opposite thalamus by a flattened gray band, the interthalamic adhesion. Whereas the lateral part of the thalamus is known as neo thalamus as it is the phylogenetically newest part of the thalamus, which includes the lateral nuclei, the pulvinar and the medial and lateral geniculate nuclei. The Dorsal surface of the thalamus is covered by white matter including stratum zonale also as it covers the dorsal surface of the thalamus. Whereas its lateral surface is covered by external lamina and nuclei is anteriorly divided by internal lamina.
Function of Thalamus
Some of the common function of thalamus is ;listed below:
1. The gray material of diencephalon which is called thalamus, consists of various nuclei and each nuclei has its specific functions like relaying information to regulating alertness and consciousness.
2. It also helps in functioning lik relaying and integrating numerous motor and sensory impulses between the higher structures of the peripheries and the brain. So, it is clear that one of the major functions of thalamus is to be involved in the relaying of sensory and motor signals to the cerebral cortex.
3. It also enables nerve fiber connections in all directions to the cerebral cortex. And the linking of each thalamus is done by the interthalamic adhesion.
4. Neurons of thalamus i.e. thalamocortical neurons generally pick up the motor or sensory information from all parts of the body and offer selected information through thalamocortical radiations to the cerebral cortex.
5. It also helps in the learning activity process, which is done by the connection of the limbic system structures to the anterior nuclei of the thalamus.
6. Thalamus also regulates functions like wakefulness and sleeping.
7. It also plays a major role in filtering impulses between the body and the brain.
8. Part of thalamus also receive visual sensory impulses from the retina to direct to the visual cortex of the occipital lobe.
Development of Thalamus
Embryonic diencephalon is the part from where thalamus is derived and in its early development stage they get divided into two progenitor domains, the caudal domain and the rostral domain. Further thalamus is divided into two groups they are allothalamus as opposed to the isothalamus.