Effect of pre-transition stimulus duration on acoustic change complex.

Objective: To investigate the effect of pre-transition duration on acoustic change complex (ACC) for speech and tonal stimulus.

Design: Cortical potentials were recorded for consonant-vowel syllable and tonal complex stimuli with varying pre-transition durations.

Study Sample: Ten individuals (three male and seven female) in the age range from 18 to 26 years, with normal hearing sensitivity, participated in the study.

Results: The results revealed that a minimum pre-transition duration of 100 ms for tonal stimulus (with spectral change) and 80 ms for consonant-vowel syllable is necessary in order to elicit ACC. The latency of N1(1) and P2(1), which is the response for change within the ongoing stimulus, increased with increase in pre-transition duration. The amplitude of the evoked responses did not show any significant change.

Conclusions: It was found that minimum pre-transition duration required in eliciting ACC for speech and non-speech stimulus is not same. The speech stimulus required lesser duration of pre-transition than non-speech stimulus. Further studies regarding the acoustic aspects of sound on CAEP in isolation are warranted.