Module 10: Figure hippocampus
Organization of the hippocampus and parahippocampal regions.
The hippocampus has a trisynaptic local circuit. The first synapses (1) are on the granule cells of the dentate gyrus (orange) that receives input from the perforant fibres. These granule cells send out axons called mossy fibres that extend into the CA3 region (blue), where they form the second group of synapses (2) by innervating the CA3 pyramidal cells. The axons from the CA3 neurons bifurcate: one part is directed down to the septum, whereas the other gives rise to Schaffer collaterals that complete the trisynaptic circuit by innervating the pyramidal neurons (3) in the CA1 region (yellow). The Schaffer collateral/hippocampal CA1 synapse (Module 10: Figure synaptic signalling mechanisms) has been studied extensively as a model for learning and memory.