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Abstract:
Speech production is one of the most complex motor skills, and involves close interaction
between the perceptual and the motor system. Recently, prediction via forward models has
been at the forefront of speech neuroscience research. For example, neuroimaging evidence
has demonstrated that activation of the auditory cortex is suppressed to self-produced speech
relative to listening without speaking. This finding has been explained via a forward model
that predicts the auditory consequences of our own speech actions. An accurate prediction
cancels out (part of) the auditory cortical activation.
The present study was designed to test two critical predictions from these frameworks: First,
whether the cortical auditory response during speech production varies as a function of the
acoustic distance between feedback and prediction, and second, whether this in turn is predictive
of the amount of adaptation in people’s speech production. MEG was recorded while
subjects performed an online speech imitation task. Each subject heard and imitated Dutch
vowels, varying in their distance from the original vowel in both F1 and F2.
The results did not show clear evidence that the amount of suppression scaled with the
distance between participants’ speech and the speech target. However, we found that subjects’
auditory response did correlate with imitation performance. This result supports the
view that an enhanced auditory response may act as an error signal, driving subsequent
speech adaptation. This suggests that individual differences in SIS could act as a marker for
subsequent adaptation.
