Dentate gyrus

Brain: Dentate gyrus
Diagram of hippocampal regions. DG: Dentate gyrus.
Coronal section of brain immediately in front of pons. (Label for "Gyrus dentatus" is at bottom left.)
Latin	gyrus dentatus
Gray's	subject #189 827
Part of	Temporal lobe
Artery	Posterior cerebral Anterior choroidal
NeuroNames	hier-161
MeSH	Dentate+Gyrus
NeuroLex ID	birnlex_1178

The dentate gyrus is part of the hippocampal formation. It is thought to contribute to new memories as well as other functional roles. It is notable as being one of a select few brain structures currently known to have high rates of neurogenesis in adult humans,^[1] (other sites include the olfactory bulb and cerebellum).^[2][3]

Structure

The dentate gyrus consists of three layers of neurons: molecular, granular, and polymorphic. The middle layer is most prominent and contains granule cells which project to the CA3 subfield of the hippocampus.^[4] These granule cells project mostly to interneurons, but also to pyramidal cells and are the principal excitatory neurons of the dentate gyrus. The major input to the dentate gyrus (the so-called perforant pathway) is from layer 2 of the entorhinal cortex, and the dentate gyrus receives no direct inputs from other cortical structures. The perforant pathway is divided into the medial perforant path and the lateral perforant path, generated, respectively, at the medial and lateral portions of the entorhinal cortex. The medial perforant path synapses onto the proximal dendritic area of the granule cells, while the lateral perforant path does so onto the distal dendrites of these same cells.

Function

The dentate gyrus is thought to contribute to the formation of memories and to play a role in depression.

Memory

The dentate gyrus is one of the few regions of the adult brain where neurogenesis (i.e., the birth of new neurons) takes place. Neurogenesis is thought to play a role in the formation of new memories. New memories could preferentially utilize newly formed dentate gyrus cell, providing a potential mechanism for distinguishing multiple instances of similar events or multiple visits to the same location.^[5] Additionally, the dentate gyrus may be important in recognizing the differences that make each place unique. Thus, damage to the dentate gyrus can play a role in déjà vu. ^[6]

Stress and Depression

The dentate gyrus may also have a functional role in stress and depression. For instance, neurogenesis has been found to increase in response to chronic treatment with antidepressants^[7]. On the contrary, however, the physiological effects of stress, often characterized by release of glucocorticoids such as cortisol, as well as activation of the sympathetic division of the autonomic nervous system, have been shown to inhibit the process of neurogenesis in primates^[8]. Both endogenous and exogenous glucocorticoids are known to cause psychosis and depression,^[9], implying that neurogenesis in the dentate gyrus may play an important role in modulating symptoms of stress and depression.

Other

Some evidence suggests that neurogenesis in the dentate gyrus increases in response to aerobic exercise^[10].

Blood Sugar

Studies by researchers at Columbia University Medical Center indicate that poor glucose control can lead to deleterious effects on the dentate gyrus.^[11]

External links

• Slide at psycheducation.org
• BrainMaps at UCDavis Dentate gyrus

• "Dentate Gyrus NMDA Receptors Mediate Rapid Pattern Separation in the Hippocampal Network". Science 7 June 2007 DOI: 10.1126/science.1140263 - The source of déjà vu
• NIF Search - Dentate Gyrus via the Neuroscience Information Framework

References