Electrical Stimulation of the Superior Olivary Complex Can Produce Cortical Evoked Potential and Behavioral Discrimination Correlates of Pitch Perception in the Rat

Abstract

Patterned electrical stimulation of the superior olivary complex (SOC) which simulated the neural frequency following response (FFR) extracellular potential was used as a stimulus in behavioral frequency discrimination and cortical evoked potential studies. Behavioral judgments of SOC stimulation frequency were found to be as accurate as those obtained for 80 dB acoustic stimuli within the spectral band of the FFR (200 to 3800 Hz). Cortical evoked potentials elicited by acoustic and electrical stimulation of the SOC were then compared for preservation of waveform similarity. Frequency dependent similarity was observed in slow wave events elicited by stimuli with frequencies in the FFR band. A 3 msec time lag was found between acoustic and SOC stimulation produced waveforms which can be accounted for by forward stimulation of the auditory pathway. Our study supports the idea that integrated extracellular waveforms of the FFR index low frequency representations in the auditory brainstem, perhaps by selecting patches of SOC cell transmembrane potential changes. Because bilateral cochlear damage did not prevent behavioral discrimination of SOC electrical stimulation, feedback to the ear is not necessary for perceptual significance of simulated FFR extracellular field potentials in the SOC.