Influence of peripheral information on behavioural and spatio-temporal neural mechanisms of vocal emotion production and perception

Pr. Didier Grandjean - FNS encouragement de projets

In recent years, a substantial body of work shed light on behavioral, electrophysiological and neural mechanisms involved in vocal emotion perception in humans (reviewed in Witteman, Van Heuven, & Schiller, 2012), namely emotional prosody defined as the supra-segmental and segmental modifications of vocal production interpreted as emotional by the listener (Grandjean, Bänziger, & Scherer, 2006). Vocal emotion recognition jointly depends on lower-level acoustic features (intonation; Bänziger & Scherer, 2005; Grandjean, Bänziger, & Scherer, 2006) and the shape of the amplitude, both of which depend on distinct neural networks (Frühholz et al., 2011) but usually recruit the superior portion of the temporal cortex (STC) and inferior frontal cortical (IFC) brain regions (Schirmer & Kotz, 2006; Witteman et al., 2012). Coherent with this body of work, Grandjean and colleagues adapted Brunswik’s lens model (Brunswik, 1956) that characterizes emotion expression by the sender, its transmission and the impression or perceived emotion by the receiver (Grandjean et al., 2006).

While abovementioned literature focused exclusively on the perceptual aspect of vocal emotion, the present project aims at shedding light on vocal emotion production mechanisms (i.e., vocal emotion expression), a topic that has been neglected so far in emotion research despite of its fundamental impact on emotion communication and social interactions. The main goal of this project is therefore to clarify behavioural and brain mechanisms of emotional vocal production in order to increase our scientific understanding of this crucial phenomenon for everyday life. Mechanisms of vocal production generally encompass respiration, phonation and articulation, which impact on several vocal parameters that in turn influence acoustic measures. In this project we will address the phenomenon of voluntary produced vocal emotional expression in a linguistic context (using for example pseudowords), and then refer to the concept of emotional prosody, as it is the most common in everyday life. We will also address nonlinguistic emotional vocalization conceptualized as affective burst. More specifically, we will seek for vocal tract dynamics related to vocal emotion production, a topic that was studied scarcely (Proctor, Bresch, Byrd, Nayak, & Narayanan, 2013). Moreover, we will focus on both proprioceptive and interoceptive feedback mechanisms in the context of speech production through both measured and induced body resonances on soft tissues that were shown to be influenced by voice fundamental frequency (i.e., perceived as pitch) on the chest of speakers (Sundberg, 1983). This information given by the mechanoreceptor systems might be fundamental both for the control of vocalizations and for the determination of the inner emotional state of the speaker, through peripheral feedbacks represented in somatosensory brain regions and in the insular cortices. Congruent with this assertion, body resonances might also be crucial for listeners in the context of the embodied theory of emotion. Such theory proposed that emotion perception is related to the capacity of the cognitive systems to simulate the body effects of emotion, a topic exclusively studied in the visual domain using face stimuli (Niedenthal, 2007; Winkielman, Coulson, & Niedenthal, 2018; Wood, Rychlowska, Korb, & Niedenthal, 2016). However, the role of emotion in such simulation mechanisms in the auditory domain have not been documented yet. We propose to address these questions through a multimethod approach combining behavioral, functional magnetic resonance imaging, electroencephalography and functional near infrared spectroscopy. Three lines of research are proposed: (i) Impact of emotional prosody production on vocal tract shapes and related brain areas involved in these mechanisms; (ii) Impact of auditory feedback and measured body resonances on vocal emotion production, perception and neural voice production mechanisms; (iii) Impact of induced body resonances on vocal emotion production, perception and neural voice production mechanisms.

Team