Alterations in prepyriform evoked potential in relation to stimulus intensity

Abstract

The single-shock prepyriform evoked potential may be described as a sinusoidal transient having the four parameters of frequency spectrum, amplitude, phase of onset, and Q. At threshold for the single-shock evoked potential averaged by computer summation, frequency and Q are maximal and amplitude and phase are minimal. With increasing stimulus intensity there is progressive increase in amplitude of the initial peak and phase of onset, and reduction in frequency and Q. Related changes take place in frequency-response curves. Up to 2 × threshold, the wave forms of evoked and spontaneous activity may be very similar. Above 2.5 × threshold, which roughly corresponds to threshold for the evoked potential in an ink tracing, there is progressive decrease in resemblance. Definitive comparisons of wave forms in different behavioral states are shown to require the use of families of evoked potentials taken over a range of stimulus intensity.