Luc ARNAL, Institut de l’Audition, Institut Pasteur, INSERM-UA06, Équipe Cognition et communication auditive
"The sound of salience: how rough sounds hijack exogenous attentional systems"
Abstract : Communication signals such as speech or music, are complex signals that exploit a large variety of acoustic features to trigger specific emotional and behavioral responses in the listener. However, the way we use some acoustic features to manipulate listeners’ affective states and reactions remains mysterious. Hypothesizing that acoustic niches (or attributes such as roughness, pitch, etc.) are naturally selected to carry specific information (danger, gender, etc.) as a function of the fitness of the stimulus and inducible reactions to promote survival, I recently showed that alarm signals (e.g. screams, sirens, but not neutral sounds like speech) exploit a restricted acoustic regime, known as roughness 14. This feature is devoted to communicate danger, enhance negative affective responses and elicit faster reactions.
Although they are scarcely present in the natural environment, rough sounds have considerable effects on perceptual, emotional and behavioral responses. Fast repetitive inputs such as strobe lights, phone vibrators or rough alarm signals induce temporally salient, annoying percepts that efficiently capture attention, even at low signal-to-noise ratio. These sounds are almost impossible to ignore or suppress perceptually, and long-term exposure to rough sounds like screams causes tremendous stress in the listener’s brain 17, sometimes leading to maladaptive reactions (e.g. shaken baby syndrome).
Here, I will describe the neural underpinning of roughness in the human brain to illuminate how these sounds take over the control of our salience system by forcing exogenous attention in time. Measuring neural responses to click trains of varying rates during intracranial recordings in eleven epileptic patients 21, I show that sounds in the roughness [30–80 Hz] range are maximally aversive by synchronizing a widespread network of subcortical and cortico-limbic regions belonging to the Salience System. In a subsequent EEG experiment, I show that aversive and electrophysiological responses to rough sounds reliably probe this system and predict inter-individual anxiety. I will argue that these results are compatible with the notion that rough sounds target the Salience System via a primitive, non-classical subcortical system involved in sensory salience and arousal.
