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

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 ({gamma}nsFS) 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 {gamma}nsFS 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 {gamma}nsFS. These results suggest that a distinct interneuron subgroup, not distracted by sensory input, mediates perceptually-relevant oscillations independent of LFP.