Mirroring the Social Aspects of Speech and Actions: The Role of the Insula.

Action and speech may take different forms, being expressed, for example, gently or rudely. These aspects of social communication, named vitality forms, have been little studied in neuroscience. In the present functional magnetic resonance imaging study, we investigated the role of insula in processing action and speech vitality forms. In speech runs, participants were asked to listen or imaging themselves to pronounce action verbs gently or rudely. In action runs, they were asked to observe or imaging themselves to perform actions gently or rudely. The results showed that, relative to controls, there was an activation of the dorso-central insula in both tasks of speech and action runs. The insula sector specific for action vitality form was located slightly more dorsally than that of speech with a large overlap of their activations. The psycho-physiological interaction analysis showed that the insular sector involved in action vitality forms processing is connected with the left hemisphere areas controlling arm actions, whereas the sector involved in speech vitality forms processing is linked with right hemisphere areas related to speech prosody. We conclude that the central part of the insula is a key region for vitality forms processing regardless of the modality by which they are conveyed or expressed.