Forward masking of the auditory evoked potentials in a bottlenose dolphin at monaural and dichotic auditory stimulation

Abstract

Short-latency auditory evoked potentials (AEPs) to paired sound pulses (the leading stimulus (masker) and the delayed stimulus (test)) were recorded non-invasively in a bottlenose dolphin Tursiops truncatus. The stimuli were played through transducers contacting the left and right acoustic windows at the lower jaw. Two types of stimulation were used: monaurally (the both stimuli played through one and the same transducer) and dichotically (the stimuli played through different transducers, contacting the left and right acoustic window). Thе masker and test stimuli were equal in level and duration characteristics. The inter-stimulus delay varied from 0.15 to 10 ms. At the monaural stimulation, the suppression of the test stimulus was constant at interstimulus intervals from 0.15 to 0.5 ms; at longer intervals, the test response recovered. At the dichotic stimulation, the deepest suppression of the test response appeared at an interval of 0.5 ms; the test response recovered at both shorter and longer intervals. The complete recovery appeared at intervals as short as 0.15 ms and as long as 2 ms. Implications of the found regularities for the preceding effect and biosonar is discussed. [Work supported by RSF (project No. 22-25-00025).]