Persistent Gamma Spiking in Non-Sensory Fast-Spiking Cells Predicts Perceptual Success

Abstract

Persistent gamma oscillations (30-55Hz) are hypothesized to temporally coordinate stimulus encoding, enabling perception. This prediction poses a conundrum: How can gamma serve as a template when the stimulus itself drives its mediators, presumably perturbing its maintenance? Specifically, fast-spiking interneurons (FS), a key gamma generator, can be highly sensory responsive. Further, the gamma-band local field potential (LFP) shows properties inconsistent with temporal coordination. Combining tetrode recording with controlled psychophysics revealed an FS subtype (γnsFS) that was not sensory responsive, whose inter-spike intervals peaked at gamma, and that fired with higher periodicity than other FS. Successful detection was predicted by increased regularity in γnsFS spiking at gamma, persisting from before to after sensory onset. In contrast, gamma LFP power negatively predicted detection, and was negatively related to gamma band spiking by γnsFS. These results suggest that a distinct interneuron subgroup, not ‘distracted’ by sensory input, mediates perceptually-relevant oscillations independent of LFP.