Vocal pitch enables differential motor learning of speech segments

Sensory feedback is crucial for maintaining accurate motor control. One process of movement correction is sensorimotor adaptation, or motor learning in response to perceived sensory errors. Recent studies have demonstrated that people can simultaneously adapt to opposing errors on a single movement (e.g., leftward and rightward errors on a reach) given some context that differentiates when each error occurs. In speech production, linguistic structure (e.g., the same vowel in different words) has been shown to provide sufficient context for adapting to opposing errors, but it is not clear whether this is restricted to the same effectors (i.e. lips, tongue, jaw in the oral cavity) or also includes movements of other effectors used in speech (i.e., the vocal folds in the larynx). While manual reaching studies have shown that contextual movements need not be produced with the same effector as the learning target, they have thus far only tested left-right effector pairs. We present the results of three simultaneous adaptation experiments in speech that examine whether laryngeal movements for pitch control can provide context for oral articulatory movements for vowels. In each experiment, the resonances that correlate with articulator position during vowels were perturbed in three different directions that were predictable given a pitch context. First, Mandarin speakers differentially adapted given pitch contexts that signaled differences in word meaning, suggesting that lexical uses of pitch provide context for vowels. Second, English speakers differentially adapted given different arbitrary pitch matching contexts on the word “head”, suggesting that even non-meaningful pitch movements provide context for vowels. Third, English speakers were unable to differentially adapt when simply listening to a contextual pitch, indicating that mere auditory input of pitch is insufficient. Together, these results indicate that sensorimotor context for learning can be provided by different effectors than the learning target.