EEG Spatiotemporal Patterns Underlying Self-other Voice Discrimination

Abstract

There is growing evidence showing that the representation of the human “self” recruits special systems across different functions and modalities. Compared to self-face and self-body representations, few studies have investigated neural underpinnings specific to self-voice. Moreover, self-voice stimuli in those studies were consistently presented through air and lacking bone conduction, rendering the sound of self-voice stimuli different to the self-voice heard during natural speech. Here, we combined psychophysics, voice-morphing technology, and high-density EEG in order to identify the spatiotemporal patterns underlying self-other voice discrimination (SOVD) in a population of 26 healthy participants, both with air- and bone-conducted stimuli. We identified a self-voice-specific EEG topographic map occurring around 345 ms post-stimulus and activating a network involving insula, cingulate cortex, and medial temporal lobe structures. Occurrence of this map was modulated both with SOVD task performance and bone conduction. Specifically, the better participants performed at SOVD task, the less frequently they activated this network. In addition, the same network was recruited less frequently with bone conduction, which, accordingly, increased the SOVD task performance. This work could have an important clinical impact. Indeed, it reveals neural correlates of SOVD impairments, believed to account for auditory-verbal hallucinations, a common and highly distressing psychiatric symptom.

Talking Heads: Bone conduction facilitates self-other voice discrimination

“…High task sensitivity also enabled us to observe that the bone-conduction advantage is most advantageous for other-dominant self-other voice morphs (i.e., containing more other-voice features). This was observed in Study 3 in both self-other and self-familiar tasks (left side of psychometric curves on Fig 3), and replicated in a follow-up EEG study with an independent cohort of participants performing the same self-other task with five times more trials 54 . This suggests that, rather than labelling an ambiguous voice as 'self', bone conduction facilitates discarding an ambiguous voice as being 'not self'.…”

“…While previous self-voice tasks have been characterized by ceiling effects, the paradigm proposed here is able to capture inter-subject variability, which allows us to dissect perceptual specificities (e.g., a bias, general sensitivity, or effects specific to self-or other-voice perception) and personalize studies of self-other VD. Most participants in Studies 1 and 3 (as well as in our follow-up EEG study 54 spontaneously reported that they perceived the self-other VD task to be very difficult and showed poor metacognition, that is they misjudged their ability of successfully performing the task. Moreover, in Study 1 we observed large differences in performance across participants.…”

“…Lower intercepts for bone conduction (asterisks in the left end of plots in Fig. 3) indicate that the accuracy in self-related tasks was more increased for otherdominant voice morphs (i.e., containing lower rate of self-voice present) 54 .…”

“…For each voice morph, participants were instructed to indicate whether the voice they heard more closely resembled their own or someone else's voice by pressing on one of two buttons. Based on our previous work 53,54 , six voice ratios (% self-voice: 15, 30, 45, 55, 70, 85; Fig. 1A) were chosen and repeated 10 times within a block in a randomized order (total of 60 trials).…”

Breathing affects self‐other voice discrimination in a bodily state associated with somatic passivity

“…Here, we investigated cardiac and respiratory phase dependency of self‐voice perception. We recorded heartbeat and respiration signals of healthy participants performing two self‐related auditory tasks (self‐other voice discrimination; loudness judgment) (Iannotti et al, 2021 ; Orepic et al, 2021 ). We investigated whether self‐voice perception would differ in trials occurring during different phases of respiratory (inspiration, expiration) and heartbeat (systole, diastole) cycles.…”