Emotional sounds in space: asymmetrical representation within early-stage auditory areas.

Evidence from behavioral studies suggests that the spatial origin of sounds may influence the perception of emotional valence. Using 7T fMRI we have investigated the impact of the categories of sound (vocalizations; non-vocalizations), emotional valence (positive, neutral, negative) and spatial origin (left, center, right) on the encoding in early-stage auditory areas and in the voice area. The combination of these different characteristics resulted in a total of 18 conditions (2 categories x 3 valences x 3 lateralizations), which were presented in a pseudo-randomized order in blocks of 11 different sounds (of the same condition) in 12 distinct runs of 6 min. In addition, two localizers, i.e., tonotopy mapping; human vocalizations, were used to define regions of interest. A three-way repeated measure ANOVA on the BOLD responses revealed bilateral significant effects and interactions in the primary auditory cortex, the lateral early-stage auditory areas, and the voice area. Positive vocalizations presented on the left side yielded greater activity in the ipsilateral and contralateral primary auditory cortex than did neutral or negative vocalizations or any other stimuli at any of the three positions. Right, but not left area L3 responded more strongly to (i) positive vocalizations presented ipsi- or contralaterally than to neutral or negative vocalizations presented at the same positions; and (ii) to neutral than positive or negative non-vocalizations presented contralaterally. Furthermore, comparison with a previous study indicates that spatial cues may render emotional valence more salient within the early-stage auditory areas.

Processing pathways for emotional vocalizations.

Emotional sounds are processed within a large cortico-subcortical network, of which the auditory cortex, the voice area, and the amygdala are the core regions. Using 7T fMRI, we have compared the effect of emotional valence (positive, neutral, and negative) and the effect of the type of environmental sounds (human vocalizations and non-vocalizations) on neural activity within individual early stage auditory areas, the voice area, and the amygdala. A two-way ANOVA was applied to the BOLD time course within each ROI. In several early stage auditory areas, it yielded a significant main effect of vocalizations and of valence, but not a significant interaction. Significant interaction as well as significant main effects of vocalization and of valence were present in the voice area; the former was driven by a significant emotional modulation of vocalizations but not of other sounds. Within the amygdala, only the main effect of valence was significant. Post-hoc correlation analysis highlighted coupling between the voice area and early stage auditory areas during the presentation of any vocalizations, and between the voice area and the right amygdala during positive vocalizations. Thus, the voice area is selectively devoted to the encoding of the emotional valence of vocalizations; it shares with several early stage auditory areas encoding characteristics for vocalizations and with the amygdala for the emotional modulation of vocalizations. These results are indicative of a dual pathway, whereby the emotional modulation of vocalizations within the voice area integrates the input from the lateral early stage auditory areas and from the amygdala.