Towards neurophysiological assessment of phonemic discrimination: Context effects of the mismatch negativity

Objective - This study focusses on the optimal paradigm for simultaneous assessment of auditory and phonemic discrimination in clinical populations. We investigated (a) whether pitch and phonemic deviants presented together in one sequence are able to elicit mismatch negativities (MMNs) in healthy adults and (b) whether MMN elicited by a change in pitch is modulated by the presence of the phonemic deviants. Methods - Standard stimuli [i] were intermixed with small, medium or large pitch deviants or with pitch deviants of the same magnitude together with small and large phonemic deviants, [y] and [u], respectively. Results - When pitch and phonemic deviants were presented together, only the large pitch and phonemic contrasts elicited significant MMNs. When only pitch deviants were presented, the medium and large pitch contrasts elicited significant MMNs. The MMNs, in response to the medium and large pitch contrasts, were of similar magnitude across the two contexts. Conclusions - Pitch and phonemic deviants can be tested together provided the pitch contrast is relatively large. Significance - A combined neurophysiological test of phonemic and pitch discrimination, as measured by the MMN, is a time-effective tool that may provide valuable information about the underlying cause of poorly specified phonemic representations in clinical populations