Event‐related vertex potentials preceding vowel onset

Neural events prior to speech were determined by averaging vertex‐recorded potentials 512 ms before vocalization. In a manner analogous to auditory‐evoked potentials, it would seem plausible to identify specific sites along motor pathways that yield cortically recordable electrical potentials that are precursory to vocalization. In this study, subjects repeatedly phonated a schwa 500 times. The repetition rate was approximately 8/min with the subject initiating each trial. The onset of vocalization was detected by a throat microphone that provided the trigger. The sample rate (25 000 samples/s) was sufficient to observe brief time periods (10 ms) along the averaged prespeech time epoch. The results indicated that repeatable, biphasic potentials were obtained during the time period between 45 and 250 ms before the onset of the vowel trigger. Interwave latencies between wavelets were highly related within and between subjects. The technique of event‐related potentials may be a useful procedure for studying ...