Excitation and inhibition differentially control slow and fast gamma. A, Pharmacology of SG and FG. Field potentials were analyzed during baseline and during the application of drugs to block fast GABAergic (BMI, 10 μm) and glutamatergic (DNQX, 10 μm) transmission. Filtered traces within each frequency band and conditions are shown. The red lines indicate the threshold (mean ± 2 SD) for significant gamma events. The dashed boxes indicate the expanded trace shown below. The effects of DNQX and BMI were tested in different experiments. Note that activity in the SG and FG bands is not eliminated by either drug on its own. The scale bars on the bottom apply to all traces. B, Representative power spectrums from experiments with bicuculline (left) and DNQX, followed by DNQX plus bicuculline (right). The insets are a magnified view showing the effect on FG. C, Normalized group mean spectral power in each gamma band during DNQX, BMI, DNQX plus BMI, and APV. The data segments analyzed were taken from 3–6 min after bath application of the drugs. Both SG and FG spectral power were reduced by BMI (top left). SG but not FG spectral power was reduced by DNQX (top right). Coapplication of BMI and DNQX reduced SG and FG power (bottom left). Neither SG nor FG was on average reduced by NMDA receptor blockade using APV (bottom right). *p < 0.05.