Interneurones

Interneurones are neurons that form connections between other neurons within the central nervous system and, in some cases, between the CNS and peripheral nerves. They are diverse in shape and function and form the local circuitry that processes information in the brain and spinal cord.

Interneurones can be inhibitory or excitatory. The majority of CNS inhibitory interneurons use GABA or glycine, while excitatory interneurons use glutamate. Most interneurones are local, wiring short distances within a region, but some are longer-range with axons that connect different brain areas.

They act to integrate and modulate signals, participate in reflexes, rhythms, and timing, and contribute to higher brain functions such as perception and memory. Interneurones form circuits that implement feedforward and feedback inhibition, as well as lateral inhibition, shaping responses of neural networks.

Examples include spinal interneurons such as Ia inhibitory interneurons, which mediate reciprocal inhibition between muscles, and Renshaw cells, which modulate motor neuron output. In the cerebral cortex and hippocampus, interneurones come in many types (parvalbumin-, somatostatin-, VIP-positive) that regulate excitation and synchronization.

Dysfunction of interneurones has been linked to neurological and psychiatric disorders, including epilepsy, schizophrenia, autism, and motor disorders. The study of interneurones highlights their central role in controlling the flow of information within neural circuits and coordinating complex behaviors.