Waveform morphology of pre-speech brain electrical potentials

Abstract

The inter- and intra-subject variations of the cortical responses before the initiation of speech were recorded. These evoked potentials were obtained at a sufficient sample rate that both slow negative waves as well as faster neurogenic signals were obtained. The marking point for determining the pre-event time epoch has been an EMG source. The data are typically acquired off-line and later averaged. This research uses a vocal signal as the marking point, and displays in real time the event-related potential. Subjects were 12 males and females. Electrodes were recorded with a silver–silver chloride electrodes positioned at Cz and using the earlobes as reference and ground. A biological preamplifier was used to amplify the weak bioelectric signals 100,000 times. Each time epoch was sampled at 20,000 samples/sec. The frequency response of these amplifiers had a high-pass of 0.1 Hz and a low-pass of 3 kHz. One second of these signals were averaged for 100 trials just prior to the subject initiation of the word “pool.” Electrical brain potentials have proven to be extremely useful for diagnosis, treatment, and research in the auditory system, and are expected to be of equal importance for the speech system.