Neural modeling and imaging of the cortical interactions underlying syllable production

Abstract

This paper describes a neural model of speech acquisition and production that accounts for a wide range of acoustic, kinematic, and neuroimaging data concerning the control of speech movements. The model is a neural network whose components correspond to regions of the cerebral cortex and cerebellum, including premotor, motor, auditory, and somatosensory cortical areas. Computer simulations of the model verify its ability to account for compensation to lip and jaw perturbations during speech. Specific anatomical locations of the model's components are estimated, and these estimates are used to simulate fMRI experiments of simple syllable production with and without jaw perturbations.2

Neural mechanisms underlying auditory feedback control of speech

“…4A). Increased bilateral activation of posterior temporal regions during perturbation speech is consistent with previous results from studies of auditory feedback disruption, including delayed auditory feedback (Hirano et al, 1997;Hashimoto and Sakai, 2003), pitch perturbation (McGuire et al, 1996;Zarate and Zatorre, 2005;Fu et al, 2006) and noise masking (Christoffels et al, 2007) Numerous lines of evidence support the hypothesis that the expected consequences of articulation and resulting auditory feedback are compared in posterior temporal cortex (see Guenther et al, 2006 for detailed discussion). Portions of posterior left PT and lateral pSTg bilaterally have been shown to respond during both speech perception and speech production in several studies (Hickok et al, 2003;Buchsbaum et al, 2005).…”

“…The no shift -baseline (t > 3.63, df = 9) contrast revealed a large network of active regions which has been previously implicated in speech production (Bohland and Guenther, 2006;Guenther et al, 2006), including bilateral peri-Sylvian auditory cortex, ventral Rolandic cortex, medial prefrontal cortex, anterior striatum, ventral thalamus, and superior cerebellum (peaking in lobule 6). Activations in the shift -baseline contrast (t > 3.41, df = 9) overlap those of the no shift -baseline contrast with two notable exceptions: extension of the superior cerebellar activation anterior-medially to include the cerebellar vermis bilaterally, and activation at the junction of the calcarine and parietal-occipital sulci.…”

“…The DIVA model was trained to produce the word /bεd/ with normal feedback (see Guenther et al, 2006 for model details). Training the model consists of repeated attempts to match a dynamic auditory target formed by extracting the first 3 formants from recorded productions of the desired speech sound by an adult male speaker.…”

“…Faster response times may be due to differences in formant and pitch control (discussed further below) but may also reflect differences in the method used to determine response latencies. Though relatively short, the latencies are sufficiently long to allow for a cortically mediated compensatory response (see Guenther et al, 2006 for discussion) and are much longer than brainstem-mediated auditory perioral reflex responses (McClean and Sapir, 1981). A recent study used transcranial magnetic stimulation to demonstrate motor cortical involvement in phonetically specific compensation to jaw perturbation with a latency of approximately 85 ms but not during short-latency perioral reflex responses with an 18 ms latency (Ito et al, 2005).…”

“…The DIVA model of speech production (Guenther et al, 1998;Guenther et al, 2006) is a quantitatively defined neuroanatomical model that provides a parsimonious account of how auditory feedback is used for both feedback control and for tuning feedforward commands. According to the model, feedforward and feedback commands are combined in primary motor cortex to produce the overall muscle commands for the speech articulators.…”