Understanding the attitude of others by hearing action sounds: the role of the insula.

During social interactions, actions and words can be expressed in different ways, for example gently, vigorously or rudely communicating the positive or negative attitude of the agent. These forms of communication are called vitality forms and play a crucial role in social relations. While the neural bases of speech and actions vitality forms have been investigated, there is no information on how we recognize others' mood/attitude by hearing the sound of their actions. In the present fMRI study we investigated the neural basis of vitality forms while participants heard action sounds in two different conditions: sounds resulting from gentle and rude actions, sounds communicating the same actions without vitality forms (control stimuli). Results showed that hearing action sounds conveying rude and gentle vitality forms respect to the control stimuli produced a specific activation of the dorso-central insula. In addition, hearing both vitality forms action sounds and control stimuli produced the activation of the parieto-frontal circuit typically involved in the observation and the execution of arm actions. In conclusion, our data indicate that, the dorso-central insula is a key region involved in the processing of vitality forms regardless of the modality by which they are conveyed.