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The trisynaptic circuit or trisynaptic loop is a relay of synaptic transmission in the hippocampus.The trisynaptic circuit is a neural circuit in the hippocampus, which is made up of three major cell groups: granule cells in the dentate gyrus, pyramidal neurons in CA3, and pyramidal neurons in CA1.
Diagram of a chemical synaptic connection. In the nervous system, a synapse [1] is a structure that allows a neuron (or nerve cell) to pass an electrical or chemical signal to another neuron or a target effector cell. Synapses can be classified as either chemical or electrical, depending on the mechanism of signal transmission between neurons.
These synaptic changes can clearly lead to modification in circuit function and to behavioral plasticity. Some patterns of synaptic activity produce an extensive increase in synaptic strength, also known as Long-Term Potentiation (LTP). In the hippocampus, LTP at Schaffer collateral-CA1 modulates the biophysical properties of AMPA receptors.
Chemical synaptic transmission is the transfer of neurotransmitters or neuropeptides from a presynaptic axon to a postsynaptic dendrite. [3] Unlike an electrical synapse, the chemical synapses are separated by a space called the synaptic cleft , typically measured between 15 and 25 nm.
Thus, Hebbian pairing of pre-synaptic and post-synaptic activity can substantially alter the dynamic characteristics of the synaptic connection and therefore either facilitate or inhibit signal transmission. In 1959, the neuroscientists, Warren Sturgis McCulloch and Walter Pitts published the first works on the processing of neural networks. [4]
A neural pathway connects one part of the nervous system to another using bundles of axons called tracts. The optic tract that extends from the optic nerve is an example of a neural pathway because it connects the eye to the brain; additional pathways within the brain connect to the visual cortex.
Calcium ions then bind to synaptotagmin proteins found within the membranes of the synaptic vesicles, allowing the vesicles to fuse with the presynaptic membrane. [16] The fusion of a vesicle is a stochastic process, leading to frequent failure of synaptic transmission at the very small synapses that are typical for the central nervous system.
The hippocampus is a structure in the brain that has been associated with various memory functions. It is part of the limbic system, and lies next to the medial temporal lobe. It is made up of two structures, the Ammon's Horn, and the Dentate gyrus, each containing different types of cells. [1]