A distributed network for speech motor adaptation

International audienceSpeech motor adaptation refers to changes in motor output in response to short but intensive periods of practice under feedback altering conditions. Speech motor adaptation has been evaluated behaviorally in response to manipulations of auditory and orosensory feedback, yielding indirect evidence of short term neural plasticity. In a recent behavioral study, we reported compelling evidence for a strong sensorimotor coupling evidenced by simultaneous changes in both speech motor output and speech perception. Here we focus on the neural changes associated with sensorimotor adaptation. Functional MRI data were acquired while subjects produced single words in the scanner. After acquiring baseline trials, auditory feedback was gradually altered (3 semitone shift) over thirty trials and then maintained for 120 trials. Changes in neural activation and acoustic speech output were assessed following the initial feedback manipulation, and over the course of the practice period. Comparison of initial and adapted periods revealed increased activations in the inferior frontal gyrus extending to the ventral premotor and primary motor cortex, in the anterior part of the insular cortex and in the superior and middle temporal gyri bilaterally. These increases gradually subsided over the course of the practice while the acoustic evidence suggested maintained compensation for the altered feedback. These results reflect the interactive nature of speech production and speech perception and suggest that speech motor adaptation results in a change in synaptic weights over the course of a single experimental session. Sensorimotor adaptation provides a robust means to assess the dynamics of brain plasticity for speech