Auditory cortical activity in normal hearing subjects to consonant vowels presented in quiet and in noise

ObjectiveCompare brain potentials to consonant vowels (CVs) as a function of both voice onset times (VOTs) and consonant position; initial (CV) versus second (VCV).MethodsAuditory cortical potentials (N100, P200, N200, and a late slow negativity, (SN) were recorded from scalp electrodes in twelve normal hearing subjects to consonant vowels in initial position (CVs: /du/ and /tu/), in second position (VCVs: /udu/ and /utu/), and to vowels alone (V: /u/) and paired (VVs: /uu/) separated in time to simulate consonant voice onset times (VOTs).ResultsCVs evoked “acoustic onset” N100s of similar latency but larger amplitudes to /du/ than /tu/. CVs preceded by a vowel (VCVs) evoked “acoustic change” N100s with longer latencies to /utu/ than /udu/. Their absolute latency difference was less than the corresponding VOT difference. The SN following N100 to VCVs was larger to /utu/ than /udu/. Paired vowels (/uu/) separated by intervals corresponding to consonant VOTs evoked N100s with latency differences equal to the simulated VOT differences and SNs of similar amplitudes. Noise masking resulted in VCV N100 latency differences that were now equal to consonant VOT differences. Brain activations by CVs, VCVs, and VVs were maximal in right temporal lobe.ConclusionAuditory cortical activities to CVs are sensitive to: (1) position of the CV in the utterance; (2) VOTs of consonants; and (3) noise masking.SignificanceVOTs of stop consonants affect auditory cortical activities differently as a function of the position of the consonant in the utterance.

► Cortical evoked potentials (N100) to speech can be recorded as “onset responses” when the consonant-vowel is in first position and as “change responses” when it follows a vowel. ► N100 latency was prolonged in consonant-vowels with long voice onset times only in change responses whereas only N100 amplitude was affected by voice onset time in onset responses. ► Source estimations indicated similar regions of cortical activation during N100 of change and onset responses to speech, whereas the sources of the subsequent slow cortical potential changed across time.