MEG CORRELATES OF CATEGORICAL PERCEPTION OF A VOICE ONSET TIME CONTINUUM IN HUMANS

Event-related magnetic fields (ERFs) were recorded from the left hemis phere in nine normal volunteers in response to four consonant-vowel (C V) syllables varying in voice-onset time (VOT). CVs with VOT values of 0 and + 20 ms were perceived as /ga/ and those with VOT values of + 4 0 and + 60 ms as /ka/. Results showed: (1) a displacement of the Nlm p eak equivalent current dipole toward more medial locations; and (2) an abrupt reduction in peak magnetic flux strength, as VOT values increa sed from + 20 to + 40 ms. No systematic differences were noted between the 0 and + 20 ms stimuli or between the + 40 and + 60 ms CVs. The fi ndings are in agreement with the results of multiunit invasive recordi ngs in non-human primates regarding the spatial and temporal pattern o f neuronal population responses in the human auditory cortex which cou ld serve as neural cues for the perception of voicing contrasts. (C) 1 998 Elsevier Science B.V. All rights reserved.