| Abstract | Feng Y, Gracco VL, Max L. Integration of auditory and somatosensory
error signals in the neural control of speech movements. J
Neurophysiol 106: 667–679, 2011. First published May 11, 2011;
doi:10.1152/jn.00638.2010.—We investigated auditory and somatosensory
feedback contributions to the neural control of speech. In task
I, sensorimotor adaptation was studied by perturbing one of these
sensory modalities or both modalities simultaneously. The first formant
(F1) frequency in the auditory feedback was shifted up by a
real-time processor and/or the extent of jaw opening was increased or
decreased with a force field applied by a robotic device. All eight
subjects lowered F1 to compensate for the up-shifted F1 in the
feedback signal regardless of whether or not the jaw was perturbed.
Adaptive changes in subjects’ acoustic output resulted from adjustments
in articulatory movements of the jaw or tongue. Adaptation in
jaw opening extent in response to the mechanical perturbation occurred
only when no auditory feedback perturbation was applied or
when the direction of adaptation to the force was compatible with the
direction of adaptation to a simultaneous acoustic perturbation. In
tasks II and III, subjects’ auditory and somatosensory precision and
accuracy were estimated. Correlation analyses showed that the relationships
1) between F1 adaptation extent and auditory acuity for F1
and 2) between jaw position adaptation extent and somatosensory
acuity for jaw position were weak and statistically not significant.
Taken together, the combined findings from this work suggest that, in
speech production, sensorimotor adaptation updates the underlying
control mechanisms in such a way that the planning of vowel-related
articulatory movements takes into account a complex integration of
error signals from previous trials but likely with a dominant role for
the auditory modality. |