The Effect of Intensity on the Speech Evoked Auditory Late Latency Response in Normal Hearing Individuals.

OBJECTIVE Among the stimulus factors, the influence of presentation level is less studied in normal-hearing individuals when using speech stimuli withvarious presentation levels for the auditory late latency response (ALLR). Hence, the present study aimed to explore the Latency-Intensity (L-I) function, i.e., how the latency and amplitude change as a function of intensity using speech stimuli. MATERIALS AND METHODS Speech-evoked ALLR was obtained from 15 normal-hearing individuals. The syllable/ta/ was used to record ALLR with an intensity of 30, 50, 70, and 90 dBSPL. Electroencephalography (EEG) from five channels was recorded and analyzed offline. RESULTS The overall results revealed that there is an influence of intensity on P1 and N1 latencies in a nonlinear fashion. The latency change is consistent at lower intensities than at moderate and high intensities. The amplitude changes did not reach significance, though a decrease with a reduction in intensity was obvious. CONCLUSION There is a significant effect of intensity on the latency and amplitude of ALLR in speech stimulus. However, this effect may vary for different speech stimuli.