Figure 8.

Recordings were made in CA1b of CA1 minislices, with a stimulus electrode placed in stratum radiatum of CA1c (see Fig. 1A). A, example of the effect of a 3 V, 35 Hz stimulus train on carbachol-evoked fast γ. B, power spectra of the recording in A 10 s before (grey line) and 10 s during 35 Hz Schaffer collateral stimulation (black line). The stimulus artefact-induced power peaks at 35 Hz and 70 Hz (grey bars) have been omitted from the analysis. Stimulation at slow γ frequency suppresses fast γ and slows it down. C, CA1b γ power (normalised to control values) as a function of frequency and intensity of Schaffer collateral stimulation trains. Data give average for seven slices. D, example of waveform averages (time-zeroed to the stimuli) of the field potential in stratum pyramidale (grey line) and the trans-membrane potential of a pyramidal cell (black line) during a 3 V, 35 Hz stimulus train. Low-intensity Schaffer collateral stimulation evoked EPSPs curtailed by IPSPs. E, waveform averages of I_m at −10 mV (black line, mainly IPSCs) and at −70 mV (grey line, mainly EPSCs, preceding the IPSC). F, waveform averages of V_m for a fast-spiking interneuron (stimuli that triggered firing were excluded) showed mainly EPSPs. Details as in D.