ACOUSTIC ELEMENTS OF SPEECHLIKE STIMULI ARE REFLECTED IN SURFACE RECORDED RESPONSES OVER THE GUINEA-PIG TEMPORAL-LOBE

Auditory evoked potentials measured from the guinea pig temporal lobe surface reflect acoustic elements of synthesized speech syllables. Eli citing stimuli included a four formant anchor stimulus /ba/, with a 40 -ms formant transition duration. The other stimuli differed from /ba/ along simple acoustic dimensions. The /pa/ stimuli differed on a VOT c ontinuum; /da/ stimuli had a higher frequency F-2 onset; /wa/ had a lo nger (80 ms) formant transition duration: and /bi/ differed in three v owel formant frequencies. The /ba/ and /da/ onset response latencies d ecreased systematically with increasing F-2 onset frequency. The respo nse to the /pa/ voicing increased in latency with increasing VOT and s howed a physiologic discontinuity at VOT of 15-20 ms. Responses to /ba / and /wa/ showed similar onset morphology but significant amplitude d ifferences at latencies corresponding to vowel onset. Significant ampl itude differences in /ba/ and /bi/ responses corresponded in latency t o both consonant and vowel portions of the syllables. Similar to previ ous reports in the awake monkey for VOT, these results demonstrate in the anesthetized guinea pig that acoustic elements essential to speech perception are reflected in aggregate response of ensembles of cortic al neurons. (C) 1996 Acoustical Society of America.