fastspiking

Fast-spiking refers to a class of inhibitory interneurons in the brain that can fire trains of action potentials at high frequencies with little or no spike-frequency adaptation and with narrow action potential waveforms. These neurons are especially prominent in the cortex and hippocampus and are GABAergic, providing rapid perisomatic inhibition to principal neurons.

Most fast-spiking interneurons express parvalbumin (PV) and include basket cells and chandelier cells. Their ability to sustain high-frequency firing is supported by molecular and biophysical properties such as a high density of Kv3 family potassium channels (notably Kv3.1 and Kv3.2), which enable rapid repolarization, as well as low input resistance and short membrane time constants.

Functionally, fast-spiking interneurons provide precise, timely inhibition to the soma and proximal dendrites of pyramidal neurons, shaping spike timing and promoting synchronization across neural networks. They are strongly implicated in generating and maintaining gamma-band oscillations (roughly 30 to 80 Hz), which are thought to support cognitive processes including attention and working memory.

Development and distribution vary by region. PV-expressing fast-spiking interneurons mature postnatally, with PV expression increasing during early development. They are abundant in the neocortex and hippocampus, and also present in other regions such as the striatum and, to a lesser extent, the cerebellum.

Clinical relevance is noted in studies of schizophrenia, epilepsy, and autism, where fast-spiking interneuron function and PV expression can be altered, contributing to disrupted gamma synchrony and cognitive symptoms. It should be noted that not all fast-spiking neurons are PV-positive, and some PV-positive cells do not conform to the classic fast-spiking profile, reflecting diversity within this group.