The rough sound of salience enhances aversion through neural synchronisation.

Being able to produce sounds that capture attention and elicit rapid reactions is the prime goal of communication. One strategy, exploited by alarm signals, consists in emitting fast but perceptible amplitude modulations in the roughness range (30-150 Hz). Here, we investigate the perceptual and neural mechanisms underlying aversion to such temporally salient sounds. By measuring subjective aversion to repetitive acoustic transients, we identify a nonlinear pattern of aversion restricted to the roughness range. Using human intracranial recordings, we show that rough sounds do not merely affect local auditory processes but instead synchronise large-scale, supramodal, salience-related networks in a steady-state, sustained manner. Rough sounds synchronise activity throughout superior temporal regions, subcortical and cortical limbic areas, and the frontal cortex, a network classically involved in aversion processing. This pattern correlates with subjective aversion in all these regions, consistent with the hypothesis that roughness enhances auditory aversion through spreading of neural synchronisation.

Human amygdala response to unisensory and multisensory emotion input: No evidence for superadditivity from intracranial recordings.

The amygdala is crucially implicated in processing emotional information from various sensory modalities. However, there is dearth of knowledge concerning the integration and relative time-course of its responses across different channels, i.e., for auditory, visual, and audiovisual input. Functional neuroimaging data in humans point to a possible role of this region in the multimodal integration of emotional signals, but direct evidence for anatomical and temporal overlap of unisensory and multisensory-evoked responses in amygdala is still lacking. We recorded event-related potentials (ERPs) and oscillatory activity from 9 amygdalae using intracranial electroencephalography (iEEG) in patients prior to epilepsy surgery, and compared electrophysiological responses to fearful, happy, or neutral stimuli presented either in voices alone, faces alone, or voices and faces simultaneously delivered. Results showed differential amygdala responses to fearful stimuli, in comparison to neutral, reaching significance 100-200 ms post-onset for auditory, visual and audiovisual stimuli. At later latencies, ∼400 ms post-onset, amygdala response to audiovisual information was also amplified in comparison to auditory or visual stimuli alone. Importantly, however, we found no evidence for either super- or subadditivity effects in any of the bimodal responses. These results suggest, first, that emotion processing in amygdala occurs at globally similar early stages of perceptual processing for auditory, visual, and audiovisual inputs; second, that overall larger responses to multisensory information occur at later stages only; and third, that the underlying mechanisms of this multisensory gain may reflect a purely additive response to concomitant visual and auditory inputs. Our findings provide novel insights on emotion processing across the sensory pathways, and their convergence within the limbic system.