The study investigates the role of fast-spiking (FS) interneurons in generating gamma oscillations (20–80 Hz) in the barrel cortex of mice. Using optogenetics, the researchers selectively activated FS interneurons with light-activated channels (ChR2) and found that this activation induced gamma oscillations in the local field potential (LFP). The activation of FS cells at frequencies within the gamma range (40 Hz) significantly amplified LFP power in that frequency band, while activation at lower frequencies did not affect LFP power. In contrast, activation of regular spiking (RS) neurons at higher frequencies (8–24 Hz) only amplified LFP power at those frequencies. The timing of sensory input relative to a gamma cycle influenced the amplitude and precision of evoked responses. The study provides causal evidence that FS cell activation is sufficient to induce gamma oscillations and suggests that these oscillations gate sensory processing by synchronizing the output of excitatory neurons.The study investigates the role of fast-spiking (FS) interneurons in generating gamma oscillations (20–80 Hz) in the barrel cortex of mice. Using optogenetics, the researchers selectively activated FS interneurons with light-activated channels (ChR2) and found that this activation induced gamma oscillations in the local field potential (LFP). The activation of FS cells at frequencies within the gamma range (40 Hz) significantly amplified LFP power in that frequency band, while activation at lower frequencies did not affect LFP power. In contrast, activation of regular spiking (RS) neurons at higher frequencies (8–24 Hz) only amplified LFP power at those frequencies. The timing of sensory input relative to a gamma cycle influenced the amplitude and precision of evoked responses. The study provides causal evidence that FS cell activation is sufficient to induce gamma oscillations and suggests that these oscillations gate sensory processing by synchronizing the output of excitatory neurons.