|Anatomical terms of neuroanatomy|
The epithalamus is a (dorsal) posterior segment of the diencephalon. The diencephalon is a part of the forebrain that also contains the thalamus, the hypothalamus and pituitary gland. The epithalamus includes the habenular nuclei and their interconnecting fibers, the habenular commissure, the stria medullaris and the pineal gland.
The function of the epithalamus is to connect the limbic system to other parts of the brain. The epithalamus also serves as a connecting point for the dorsal diencephalic conduction system, which is responsible for carrying information from the limbic forebrain to limbic midbrain structures. Some functions of its components include the secretion of melatonin and secretion of hormones from the pituitary gland (by the pineal gland circadian rhythms), regulation of motor pathways and emotions, and how energy is conserved in the body.
A study has shown that the lateral habenula, an epithalamic structure, produces spontaneous theta oscillatory activity that was correlated with theta oscillation in the hippocampus. The same study also found that the increase in theta waves in both lateral habenula and hippocampus was correlated with increased memory performance in rats. This suggests that the lateral habenula has an interaction with the hippocampus that is involved in hippocampus-dependent spatial information processing.
Species that possess a photoreceptive parapineal organ show asymmetry in the epithalamus at the habenula, to the left (dorsal).
Dysfunction of the epithalamus can be related to mood disorders, such as major depression, schizophrenia and sleeping disorders. Low levels of melatonin will typically give rise to mood disorders.
The epithalamus is associated with sleep disorders like insomnia revolving around circadian rhythms of sleep wake cycles. The close connection of the epithalamus with the limbic system regulates the secretion of melatonin by the pineal gland and the regulation of motor pathways and emotions. The secretion of melatonin happens in a cycle. Secretion is high at night or in the absence of light and low during the day. The suprachiasmatic nucleus in the hypothalamus is responsible for this cycle of secretion from the epithalamus, specifically from the pineal gland. The Circadian timekeeping is driven in cells by the cyclical activity of core clock genes and proteins such as per2/PER2. Gamma-aminobutyric acid and several peptide factors, including cytokines, growth hormone-releasing hormone and prolactin, are related to sleep promotion.
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- NIF Search - Epithalamus via the Neuroscience Information Framework