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. Author manuscript; available in PMC: 2012 Oct 20.
Published in final edited form as: Neuron. 2011 Oct 20;72(2):231–243. doi: 10.1016/j.neuron.2011.09.027

Figure 7.

Figure 7

Inhibition is an essential component of synchronous oscillations in cortical activity. A, Simultaneous recording of gamma frequency (~40 Hz) oscillations in the local field potential (LFP) and the inhibitory (blue) and excitatory (red) postsynaptic currents recorded in two nearby pyramidal cells in hippocampal slices. While the amplitude of the LFP and synaptic currents varies on a cycle-to-cycle basis, the ratio of excitation to inhibition remains constant. B, In vivo recordings of spontaneous gamma oscillations in the hippocampus reveal that the phase-specific firing of action potentials (green) relative to the local field potential coincides with a brief time window during which synaptic excitation (red) precedes inhibition (blue). C, In vivo recordings from olfactory cortex reveal odor-evoked beta frequency (~20 Hz) oscillations in the local field potential and inhibitory and excitatory postsynaptic currents in a pyramidal cell. D, In olfactory cortex, phase-specific firing of action potentials (bottom histogram) relative to the local field potential (top) coincides with the brief time window during which odor-evoked synaptic excitation (red) precedes inhibition (blue). A and B modified from (Atallah and Scanziani, 2009). C and D modified from (Poo and Isaacson, 2009).