Trisynaptic loop
Encyclopedia
The trisynaptic loop is a relay of synaptic transmission in the hippocampus
, which is made up of three major cell groups: granule cells, CA3 ("Cornu Ammonis" area 3) pyramidal neurons, and CA1 ("Cornu Ammonis" area 1) pyramidal cells. The hippocampal relay involves 3 main regions within the hippocampus which are classified according to their cell type and projection fibers. The first projection of the hippocampus occurs between the entorhinal cortex
and the dentate gyrus
. The entorhinal cortex transmits its signals from the parahippocampal gyrus to the dentate gyrus via granule cell fibers known collectively as the perforant path. The dentate gyrus then synapses on pyramidal cells in CA3 via mossy cell fibers. CA3 then fires to CA1 via Schaffer collaterals which synapse in the subiculum and are carried out through the fornix. Collectively the dentate gyrus, CA1 and CA3 of the hippocampus compose the trisynaptic loop.
EC → DG via the perforant path(synapse 1), DG → CA3 via mossy fibres(synapse 2), CA3 → CA1 via schaffer collaterals(synapse 3)
Criticism: Recent anatomical methods challenge the simple notion of tri-synaptic circuit
[1] Amaral DG, Witter, MP. 1995. Hippocampal formation. In: Paxinos G, editor. The rat nervous system, 2nd ed. San Diego: Academic Press.
Hippocampus
The hippocampus is a major component of the brains of humans and other vertebrates. It belongs to the limbic system and plays important roles in the consolidation of information from short-term memory to long-term memory and spatial navigation. Humans and other mammals have two hippocampi, one in...
, which is made up of three major cell groups: granule cells, CA3 ("Cornu Ammonis" area 3) pyramidal neurons, and CA1 ("Cornu Ammonis" area 1) pyramidal cells. The hippocampal relay involves 3 main regions within the hippocampus which are classified according to their cell type and projection fibers. The first projection of the hippocampus occurs between the 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...
and 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...
. The entorhinal cortex transmits its signals from the parahippocampal gyrus to the dentate gyrus via granule cell fibers known collectively as the perforant path. The dentate gyrus then synapses on pyramidal cells in CA3 via mossy cell fibers. CA3 then fires to CA1 via Schaffer collaterals which synapse in the subiculum and are carried out through the fornix. Collectively the dentate gyrus, CA1 and CA3 of the hippocampus compose the trisynaptic loop.
EC → DG via the perforant path(synapse 1), DG → CA3 via mossy fibres(synapse 2), CA3 → CA1 via schaffer collaterals(synapse 3)
Criticism: Recent anatomical methods challenge the simple notion of tri-synaptic circuit
[1] Amaral DG, Witter, MP. 1995. Hippocampal formation. In: Paxinos G, editor. The rat nervous system, 2nd ed. San Diego: Academic Press.