Figure 2. Gamma oscillation stimulation protocol and analysis.

A. Neurons were stimulated with a constant level (I_base) of depolarizing current (middle) and a fluctuating hyperpolarizing current (top). On each 500 ms long trial, stimuli were constructed by randomly adding one of ten levels of tonic inhibition (“input mean”) (equal intervals, ranging from 0 to I_base) to a zero-mean 40 Hz oscillatory current (“input synchrony”) with a amplitude of a one of ten randomly selected values (equal intervals, ranging from 0 to I_base).

B. Sample responses to low-mean, low-synchrony inputs (a), low-mean, high-synchrony inputs (b), and high-mean, low-synchrony inputs (c). d: The cell's responsiveness (black to white) systematically varied with mean inhibitory current (vertical axes) and inhibitory synchrony (horizontal axes). Responsiveness was reduced as the amount of inhibition increased (green vertical overlay), and increased as the inhibition became more synchronized (green horizontal overlay).

Ca. Dependence of spike rate on input synchrony, for each level of mean inhibition. Green line represents the green-highlighted horizontal segment of Bd. Lighter grey = less mean inhibition. b: Dependence of output spike rate on mean inhibition, for each level of input synchrony. Green line represents the green-highlighted vertical segment of Bd. Lighter gray = more inhibitory synchrony.