Fig. 7.

Saturation of afterhyperpolarization did not account for the sigmoidal f–I relationship of subthalamic neurons because afterhyperpolarization accumulated during high-frequency firing. A, B, Representative example of a spontaneously firing subthalamic neuron, which was injected with an increasing magnitude of current. Note that the time to the resumption of spontaneous firing, a measure of afterhyperpolarization, increased as both elicited firing frequency and driving current increased.