Oscillatory coherence of prototypic GPe neurons. A, Experimental arrangement. GPe cells recorded in perforated patch were injected with sinusoidal currents with frequencies from 1 to 100 Hz. The phase of every action potential with respect to the current waveform was measured. B, Examples of firing driven by 20 pA sinusoidal currents at three different stimulus frequencies in the same identified prototypic GPe neuron. C, Interval-by-interval firing rates (1/interspike interval) during the first 1 s of a 10 s sinusoidal stimulation at each frequency for the neuron in B. D, Histograms represent the probability of firing as a function of stimulus phase in the same neuron at the same three frequencies. Dashed-line histograms superimposed represent control histograms for spontaneous firing (zero amplitude oscillations). The control vector strengths were 0.001, 0.097, and 0.065 for 3, 34, and 100 Hz, respectively. E, Spike-oscillation coherence measured by vector strength (above) and vector angle (below) for the same cell over the range of stimulus frequencies. Dashed line indicates the neuron’s spontaneous firing rate. The coherence spectra for each cell in the sample are shown in Extended Data Figure 1-1. F, The average number of action potentials per stimulus cycle for the neuron in B–E, at each stimulus frequency. Inset, Distribution of the number of stimulus cycles per action potential at stimulus frequency of 100 Hz. G, The frequency at the peak of coherence (maximum vector strength) versus unperturbed firing rate in the sample of 20 GPe neurons.