Dentate gyrus

The dentate gyrus is part of the hippocampal formation. It is thought to contribute to new memories and to regulate happiness.

Structure
The dentate gyrus contains granule cells, which project to the pyramidal cells, but mostly to the interneurons of the CA3 subfield of the hippocampus. The granule cells 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 new memories and to regulate happiness.

Memory
The dentate gyrus is one of the few regions of the brain where neurogenesis takes place. Neurogenesis is thought to play a role in the formation of new memories. Such memories might furthermore be of the ones recognizing the differences that make each place unique. Thus, damage to the dentate gyrus can play a role in déjà vu.

Happiness
The dentate gyrus is also thought to regulate happiness. For instance, it has been found to increase in response to both antidepressants. On the converse, however, endogenous and exogenous glucocorticoids such as cortisol inhibit neurogenesis. Both endogenous and exogenous glucocorticoids are known to cause psychosis and depression,, implying that neurogenesis may improve symptoms of depression. As another example, electrical chatter in the dentate gyrus contracts in depressed rats but expands again after the animals receive antidepressants. The region may represent a common pathway or intersection for brain activity in those suffering from depression

Others
The dentate gyrus has also been found to increase in response to aerobic exercise.