Interneuronit

Interneuronit, commonly called interneurons in English, are neurons that form connections within a local circuit rather than projecting long distances. They connect neighboring neurons in the brain or spinal cord, shaping the flow of information, timing, and synchronization within a region. Most interneurons are inhibitory, while a smaller number can be excitatory depending on the circuit.

In the cerebral cortex and hippocampus they are diverse in shape and function. The majority use the neurotransmitter GABA (often with GAD65/67 as markers) to generate inhibitory postsynaptic potentials that regulate the activity of principal neurons. Morphologies include basket cells, which provide perisomatic inhibition; chandelier cells, which target the axon initial segment; stellate and granule-like interneurons, which provide dendritic or local inhibition. There are also subtypes defined by molecular markers such as parvalbumin, somatostatin, VIP, and calretinin, reflecting distinct genetic programs and connectivity.

Interneurons participate in critical network operations, including feedforward and feedback inhibition, gain control, and the generation of neural oscillations (for example, gamma rhythms). By coordinating excitation and inhibition they help refine sensory processing, motor control, and learning. They are integrated into layered cortical circuits and hippocampal circuits, and they interact with projection neurons to create functional microcircuits.

Development and clinical relevance: Interneurons originate from progenitors in the developing brain and migrate into cortical and subcortical regions. Disturbances in interneuron development or function are linked to neurological and psychiatric conditions such as epilepsy, schizophrenia, and autism. Research employs electrophysiology, optogenetics, calcium imaging, and computational models to understand their roles in health and disease.