Area Spt in the Human Planum Temporale Supports Sensory-Motor Integration for Speech Processing

Abstract

Processing incoming sensory information and transforming this input into appropriate motor responses is a critical and ongoing aspect of our moment-to-moment interaction with the environment. While the neural mechanisms in the posterior parietal cortex (PPC) that support the transformation of sensory inputs into simple eye or limb movements has received a great deal of empirical attention-in part because these processes are easy to study in nonhuman primates-little work has been done on sensory-motor transformations in the domain of speech. Here we used functional magnetic resonance imaging and multivariate analysis techniques to demonstrate that a region of the planum temporale (Spt) shows distinct spatial activation patterns during sensory and motor aspects of a speech task. This result suggests that just as the PPC supports sensorimotor integration for eye and limb movements, area Spt forms part of a sensory-motor integration circuit for the vocal tract.

Auditory Cortex Encodes the Perceptual Interpretation of Ambiguous Sound

“…Macroscopically, area PT has been described as a computational hub, which segregates spectrotemporal patterns, compares them to stored patterns, and outputs auditory objects (Griffiths and Warren, 2002), which is compatible with our results. Location and functional role of a smaller part of our clusters in PT is accordant with Spt, a functional subdivision of PT, which has been described as a sensory-motor integration region for the vocal tract motor effector (Hickok and Poeppel, 2007;Hickok et al, 2009). This is in line with the suggestion that PT is part of the dorsal stream of auditory processing (revised to include language in addition to spatial functions) and possesses the representation of templates for doable articulations, effectively disambiguating phonological information (Rauschecker and Scott, 2009).…”

Decoding Articulatory Features from fMRI Responses in Dorsal Speech Regions

“…Left hemispheric motor speech areas have been found to be involved both in the subvocal rehearsal and perception of the syllables /ba/ and /da/ (Pulvermüller et al, 2006) and of spoken words (Schomers et al, 2014). Furthermore, speech motor regions may bias the perception of ambiguous speech syllables under noisy conditions (D'Ausilio et al, 2009;Du et al, 2014) and have been suggested to be specifically important for the performance of tasks requiring subvocal rehearsal (Hickok and Poeppel, 2007;Krieger-Redwood et al, 2013). However, the involvement of (pre)motor cortex in speech perception may also reflect an epiphenomenal consequence of interconnected networks for speech perception and production .…”

“…Specifically, the anterior SMG was found to generalize manner of articulation in the right hemisphere and place of articulation in the left (10 mm searchlight radius) and right (20 mm searchlight radius) hemisphere. Nearby regions involving the inferior parietal lobe (Raizada and Poldrack, 2007;Moser et al, 2009;Kilian-Hü tten et al, 2011) and sylvian-parietaltemporal regions (Caplan and Waters, 1995;Hickok et al, 2003Hickok et al, , 2009Buchsbaum et al, 2011) have been implicated in sensorimotor integration during speech perception as well as in mapping auditory targets of speech sounds before the initiation of speech production Guenther and Vladusich, 2012). Here, we show the sensitivity of SMG to represent articulatory features of spoken syllables during speech perception in the absence of an explicit and active task, such as repetition (Caplan and Waters, 1995;Hickok et al, 2009) or music humming (Hickok et al, 2003).…”

“…Correspondingly, the neural processes responsible for both faculties are inherently connected (Hickok and Poeppel, 2007;Glasser and Rilling, 2008), with sensorimotor integration subserving transformations between acoustic (perceptual) and articulatory (motoric) representations . Although sensorimotor integration mediates motor speech development and articulatory control during speech production (Guenther and Vladusich, 2012), its role in speech perception is less established.…”

“…Indeed, it remains unknown whether articulatory speech representations play an active role in speech perception and/or whether this is dependent on taskspecific sensorimotor goals. Tasks explicitly requiring sensoryto-motor control, such as speech repetition (Caplan and Waters, 1995;Hickok et al, 2009), humming (Hickok et al, 2003), and verbal rehearsal in working memory (Baddeley et al, 1998;Jacquemot and Scott, 2006;Buchsbaum et al, 2011), activate the dorsal auditory pathway, including sensorimotor regions at the border of the posterior temporal and parietal lobes, the sylvian-parieto-temporal region and supramarginal gyrus (SMG) (Hickok and Poeppel, 2007). Also, in experimental paradigms that do not explicitly require sensorimotor integration, the perception of speech may involve a coactivation of motor speech regions (Zatorre et al, 1992;Wilson et al, 2004).…”