Speech motor learning alters auditory and somatosensory event-related potentials

Abstract

Speech motor learning is dependent upon changes to motor function, but it also results in changes to sensory systems. However, the neural mechanisms of sensory plasticity associated with speech motor learning are little understood. We here examined whether auditory and somatosensory cortical processes are changed in conjunction with speech motor learning. We tested native speakers of American English. Altered auditory feedback (AAF) training was used as a motor learning task. As subjects repeated aloud the speech utterance “head,” the produced sound was feedbacked through headphones while the first formant of /ea/ was gradually decreased over 50 repetitions and held at a maximum change for 110 repetitions. In order to evaluate the effects of the resulting adaptation on cortical sensory processes, we recorded auditory and somatosensory event-related potentials (ERPs) using 64-channel electroencephalography before and after AAF training. Auditory ERPs were elicited by using the synthesized vowel sound “e.” Somatosensory ERPs were elicited by facial skin deformation. We found changes to auditory and somatosensory ERPs following AAF training in individuals who showed adaptation to altered auditory feedback. The changes in ERPs were correlated with the amount of adaptation. This suggests that speech motor learning alters somatosensory and auditory cortical processing.