The fascia dentata is the earliest stage of the hippocampal circuit. Its primary input is the perforant path

Perforant path

In the brain, the perforant pathway provides a connectional route from the entorhinal cortex to all fields of the hippocampal formation, including the dentate gyrus, all CA fields , and the subiculum....

 from the superficial layers of entorhinal cortex

Entorhinal cortex

The entorhinal cortex is located in the medial temporal lobe and functions as a hub in a widespread network for memory and navigation. The EC is the main interface between the hippocampus and neocortex...

. Its principal neurons are tiny granule cells which give rise to unmyelinated

Myelin

Myelin is a dielectric material that forms a layer, the myelin sheath, usually around only the axon of a neuron. It is essential for the proper functioning of the nervous system. Myelin is an outgrowth of a type of glial cell. The production of the myelin sheath is called myelination...

 axons called the mossy fiber

Mossy fiber (hippocampus)

In the hippocampus, granule cells of the dentate gyrus form distinctive unmyelinated axons that project along the mossy fiber pathway to the CA3 region. The axons emerge from the basal portions of the granule cells and pass through the hilus of the dentate gyrus before entering the stratum...

s which project to the hilus

Hilum (anatomy)

In human anatomy, the hilum is a depression or fissure where structures such as blood vessels and nerves enter an organ.-Examples of hila:* Hilum of kidney, admits the renal artery, vein, ureter, and nerves...

 and CA3. The fascia dentata of the rat contains approximately 1,000,000 granule cells. It receives feedback connections from mossy cells in the hilus at distant levels in the septal and temporal directions. The fascia dentata and the hilus together make up the dentate gyrus

Dentate gyrus

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 rats, .The dentate gyrus cells receive...

. As with all regions of the hippocampus, the dentate gyrus also receives GABAergic

Gabâ

Gabâ or gabaa, for the people in many parts of the Philippines), is the concept of a non-human and non-divine, imminent retribution. A sort of negative karma, it is generally seen as an evil effect on a person because of their wrongdoings or transgressions...

 and cholinergic

Acetylcholine

The chemical compound acetylcholine is a neurotransmitter in both the peripheral nervous system and central nervous system in many organisms including humans...

 input from the medial septum and the diagonal band of Broca

Diagonal band of Broca

The diagonal band of Broca forms the medial margin of the anterior perforated substance.-Contents:It consists of fibers that are said to arise in the parolfactory area, the gyrus subcallosus and the anterior perforated substance, and course backward in the longitudinal striae to the dentate gyrus...

.