Multisynapse

Multisynapse is a term used in neuroscience to describe a synaptic arrangement in which multiple synaptic contacts are established between neurons, or a neuron forms several synapses onto multiple postsynaptic targets. The concept emphasizes that communication in neural circuits often involves more than a single connection, which can influence how signals are transmitted and integrated.

Anatomically, multisynapse can refer to several patterns. One pattern is a single presynaptic neuron forming multiple distinct synapses onto a single postsynaptic neuron, often distributed along different parts of the dendritic tree or near the soma. Another pattern is a neuron forming synapses with multiple postsynaptic targets (divergence) or creating several boutons onto the same target. These arrangements can occur in various brain regions, including cortex and hippocampus, and may involve both axo-axonic and axo-dendritic contacts.

Functionally, multisynaptic connectivity can increase the overall strength and reliability of signal transmission, support complex temporal and spatial integration, and provide redundancy against the failure of individual synapses. The presence of multiple contacts can also shape plasticity, allowing coordinated changes across several synapses during learning and development.

Developmentally, multisynapses often arise during exuberant synaptogenesis and are later refined by activity-dependent pruning as circuits mature. Studying multisynapses typically involves high-resolution imaging and reconstruction of synaptic contacts, including electron microscopy, advanced light microscopy, and connectomics approaches, as well as electrophysiological methods to assess functional connectivity.

See also: synapse, synaptic plasticity, connectomics, neural circuit, polysynaptic pathway.