Mean-based neural coding of voices

Abstract

The social significance of recognizing the person who talks to us is obvious, but the neural mechanisms that mediate talker identification are unclear. Regions along the bilateral superior temporal sulcus (STS) and the inferior frontal cortex (IFC) of the human brain are selective for voices, and they are sensitive to rapid voice changes. Although it has been proposed that voice recognition is supported by prototype-centered voice representations, the involvement of these category-selective cortical regions in the neural coding of such "mean voices" has not previously been demonstrated. Using fMRI in combination with a voice identity learning paradigm, we show that voice-selective regions are involved in the mean-based coding of voice identities. Voice typicality is encoded on a supra-individual level in the right STS along a stimulus-dependent, identity-independent (i.e., voice-acoustic) dimension, and on an intra-individual level in the right IFC along a stimulus-independent, identity-dependent (i.e., voice identity) dimension. Voice recognition therefore entails at least two anatomically separable stages, each characterized by neural mechanisms that reference the central tendencies of voice categories.

Voice-sensitive brain networks encode talker-specific phonetic detail

“…Recall that the typicality analysis collapsed both Long and Short VOT variants for both talkers (each of which might be perceived as ‘typical’ or ‘atypical’ of a given talker according to the counterbalanced group assignment), so differences in activation seen within this contrast cannot be attributed to surface-level properties of the stimuli. Notably, right posterior temporal and parietal regions have been linked in lesion studies (Van Lancker et al, 1988, 1989) and imaging studies (Andics et al, 2010, 2013) to access to talker identity. This region also abuts a slightly more ventral MTG area that was found to be responsive in a previous study to talker-specific phonetic variability when that variability takes the form of an ambiguous phoneme inserted in a biasing lexical context (Myers & Mesite, 2014).…”

“…Imaging studies have further corroborated the separation between regions that are sensitive to the acoustics of the voice—and thus could be used for discriminating between talkers—and those responsible for mapping voice acoustics to an individual identity which can be used for talker identification (von Kriegstein, et al, 2003). In particular, while voice acoustics may be processed in bilateral temporal regions (specifically the superior temporal sulcus or STS), imaging studies have sited vocal identity processing (or access to familiar voices) in the anterior right temporal lobe rather than the right posterior region implicated in lesion studies (Andics et al, 2010; Andics, McQueen, & Petersson, 2013; Belin & Zatorre, 2003; Campanella & Belin, 2007). …”

A Neuropsychological Approach to Auditory Verbal Hallucinations and Thought Insertion - Grounded in Normal Voice Perception

“…Thus normal processing of voices involves increasingly more abstract representations of speaker identity, independent of other (e.g., acoustic) features (Warren et al 2006). Current evidence also suggests that individual voices are coded relative to how different they are from a prototypical, or average, voice (i.e., a ‘prior’; Andics et al 2013; Andics et al 2010; Latinus et al 2013), which indicates that both prediction and prediction error signals are routinely implemented in the perception of speaker identity.…”

Activation in the angular gyrus and in the pSTS is modulated by face primes during voice recognition

“…Based on the previous literature, we expected in the crossmodal condition a decrease in activation in samespeaker (person-congruent) compared with differentspeaker (person-incongruent) trials in face-sensitive areas of the fusiform gyrus [Grill-Spector et al, 2004;Shah et al, 2001] and in voice-sensitive areas along the STS [Andics et al, 2013b;Joassin et al, 2011;Latinus et al, 2011] and the inferior frontal gyrus (IFG, [Andics et al, 2013a,b;Latinus et al, 2011]). The S2 stimulus (the target) was a human voice in all conditions.…”

“…We further manipulated the congruency between the prime and the target, that is, whether the prime and the target belonged to the same speaker (person-congruent) or to different speakers (person-incongruent). Based on the previous literature, we expected in the crossmodal condition a decrease in activation in samespeaker (person-congruent) compared with differentspeaker (person-incongruent) trials in face-sensitive areas of the fusiform gyrus [Grill-Spector et al, 2004;Shah et al, 2001] and in voice-sensitive areas along the STS [Andics et al, 2013b;Joassin et al, 2011;Latinus et al, 2011] and the inferior frontal gyrus (IFG, [Andics et al, 2013a,b;Latinus et al, 2011]). We further predicted a similar decline of the BOLD signal in supramodal brain regions which have been previously reported to be activated during the integration of human faces and voices, specifically the pSTS [Blank et al, 2011;Joassin et al, 2011;Klasen et al, 2011;Watson et al, 2013Watson et al, , 2014a and the angular gyrus [Joassin et al, 2011;Klasen et al, 2011;M€ uller et al, 2011].…”