Behavioral versus electrophysiological cortical auditory change detection in pure tones and spectral ripples

The aim of the study is to investigate the clinical value of cortical evoked potentials as an objective tool to assess auditory change detection of pure tones and spectral ripple stimuli. Auditory change complexes (ACCs) were obtained in 21 clinically normal hearing subjects (responses to changes in pure tones were obtained in 13 subjects, responses to changes in spectral ripples were obtained in 14 subjects) and compared to their behavioral responses for the different stimuli. Frequency stimuli consisted of 1000-Hz pure tones with frequency changes varying from 0.1% to 50% and spectral ripples with densities varying from 0.125 to 21.5 ripples per octave, with/without 180° phase inversions. For both stimulus types, behavioral and electrophysiological difference limens were determined and compared. Results show that the electrophysiological frequency and spectral ripple difference limens were significantly less sensitive than behavioral frequency difference limens and spectral ripple difference limens. Prolonged ACC latencies were found for both stimulus types with increasing task difficulty. However, no statistically significant correlations were found between the behavioral and electrophysiological responses. Despite that ACCs might be a clinically promising objective tool to determine auditory change detection in patients who are difficult to test, such as young children, one should take into account that even clinically normal-hearing subjects show substantial variability in their behavioral and electrophysiological responses.