Functional properties of striatal fast-spiking interneurons.

Joshua D Berke

doi:10.3389/fnsys.2011.00045

Abstract

Striatal fast-spiking interneurons (FSIs) have a major influence over behavioral output, and a deficit in these cells has been observed in dystonia and Tourette syndrome. FSIs receive cortical input, are coupled together by gap junctions, and make perisomatic GABAergic synapses onto many nearby projection neurons. Despite being critical components of striatal microcircuits, until recently little was known about FSI activity in behaving animals. Striatal FSIs are near-continuously active in awake rodents, but even neighboring FSIs show uncorrelated activity most of the time. A coordinated “pulse” of increased FSI firing occurs throughout striatum when rats initiate one chosen action while suppressing a highly trained alternative. This pulse coincides with a drop in globus pallidus population activity, suggesting that pallidostriatal disinhibition may have a important role in timing or coordinating action execution. In addition to changes in firing rate, FSIs show behavior-linked modulation of spike timing. The variability of inter-spike intervals decreases markedly following instruction cues, and FSIs also participate in fast striatal oscillations that are linked to rewarding events and dopaminergic drugs. These studies have revealed novel and unexpected properties of FSIs, that should help inform new models of striatal information processing in both normal and aberrant conditions.

Highlights

The striatum is the largest component of basal ganglia circuitry, and the primary location at which information is passed into those circuits from cortex and thalamus
Perhaps the most striking finding so far is how unexpectedly Fast-spiking interneurons (FSIs) seem to behave in the context of awake circuit dynamics, compared to brain slices, anesthesia, or sleep
Whereas FSIs in slices are quiescent but strongly inhibit mediumspiny projection neurons (MSNs) when artificially stimulated, awake FSIs usually emit a near-continuous stream of single spikes whose influence on nearby MSNs is not readily detectable

Summary

SYSTEMS NEUROSCIENCE

A coordinated “pulse” of increased FSI firing occurs throughout striatum when rats initiate one chosen action while suppressing a highly trained alternative This pulse coincides with a drop in globus pallidus population activity, suggesting that pallidostriatal disinhibition may have a important role in timing or coordinating action execution. The variability of inter-spike intervals decreases markedly following instruction cues, and FSIs participate in fast striatal oscillations that are linked to rewarding events and dopaminergic drugs. These studies have revealed novel and unexpected properties of FSIs, that should help inform new models of striatal information processing in both normal and aberrant conditions

Introduction

Striatal FSIs and behavior

Findings

Conclusion