any anomaly in the dc shift in the waveform sustained for the duration of a toneburst stimulus that represents the depolarization of sensory hair cells in the cochlea; positive summating potentials (SPs) reflect activity of basal turn hair cells while negative SPs are derived from hair cell activity in the apical turn; negative SPs tend to be obtained at low frequencies and low intensities of stimulus, while positive SPs are recorded in response to high frequencies and high intensities