The precise contribution and mechanism of sensory feedback (particularly auditory feedback) in successful speech production is unclear. Some models of speech production, such as DIVA, assert that speech production is based on attempting to produce auditory (and/or somatosensory targets; e.g. Guenther et al. 2006), and thus assign a central role to sensory feedback for successful speech motor control. These models make explicit predictions about the neural basis of speech production and the integration of auditory and somatosensory feedback. These models predict basal ganglia involvement in speech motor control (qua a complex motor process), and previous work (e.g. Alm 2004) suggests that the basal ganglia play a critical role in processing speech input as well, suggesting that their function is not purely motoric.
In order to test the implications of models depending on the integration of sensory feedback for speech, we present neuroimaging studies of two disorders of speech production in the absence of apraxia or dysarthria - one acquired (Foreign Accent Syndrome; FAS) and one developmental (Persistent Developmental Stuttering; PDS). Our results broadly confirm the predictions of the extended DIVA (Bohland et al. 2010) model, and emphasize the importance of the basal ganglia, especially the basal ganglia-thalamic-cortical (BGTC) loops. I argue that FAS should be thought of as a disorder of excessive speech sensory feedback, and that fluency in PDS depends on successful integration of speech sensory feedback with feedforward control commands.