Strength-duration properties of cathodal pulses eliciting spreading depression in rat cerebral cortex

Strength-duration curves for the threshold stimulus for initiation of spreading depression were determined for durations of 2 ms to 120 s, using cathodal surface stimulation through a well-defined area. With the dura open, the strength-duration curve was of the form I square root t = constant. With extradural stimulation, the slope of the log-log plot relating current intensity to pulse duration increased gradually as the pulse duration increased.