Dentate gyrus
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The dentate gyrus is part of the hippocampal formation. It serves as the primary afferent area to the hippocampus. It contains granule cells, which project to the pyramidal cells of layers CA2-4 of the hippocampus. The granule cells, principal excitatory neurons in the dentate gyrus, receive inputs from areas in the neocortex. Most of these inputs are provided by the perforant path, the axons of spiny stellate cells at the entorhinal cortex. The perforant path is divided in 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 it onto the distal dendrites of these same cells.
The dentate gyrus is also 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. It has also been found to be increased in response to both antidepressants and physical exercise. This implies that neurogenesis may improve symptoms of depression.