Measuring Movement-Related Cerebral Potentials in
Physiological Investigations of
Speech and Nonspeech Orofacial Movements
L Patrylak, L Max
Slow potentials can be recorded with surface electrodes overlying the cortical motor areas of the brain. It is generally accepted that the first distinctly observable potential, known as the Bereitschaftspotential or Readiness Potential (RP), reflects information regarding central nervous system processes involved in the preparation of movements. In contrast to movements performed with a finger, hand, or foot, little is known about the neuromotor processes involved in the preparation of movements performed with orofacial structures such as the lips, jaw, and tongue. This lack of understanding is related to methodological difficulties associated with the recording of RPs prior to orofacial movements. Artifacts resulting from cyclic respiratory processes, from the close proximity of involved muscles to the recording electrodes on the scalp, and from the very nature of speech movements themselves have consistently hindered the application of RP measures to orofacial movements.
Work in our laboratory is aimed at investigating and optimizing the application of current electrophysiological recording techniques and procedures to the study of orofacial movements in speech. Specifically, the work reported here was designed to examine (1) whether or not appropriate triggering for backward averaging of RPs preceding speech can be achieved based on electromyographic (EMG) activity from natural movements rather than from brisk movements such as used in studies of finger movements, and (2) whether or not holding one’s breath is a necessary and sufficient control technique to avoid respiration-related artifacts in RPs prior to speech production.