Processing of emotional vocalizations in bilateral inferior frontal cortex

A current view proposes that the right inferior frontal cortex (IFC) is particularly responsible for attentive decoding and cognitive evaluation of emotional cues in human vocalizations. Although some studies seem to support this view, an exhaustive review of all recent imaging studies points to an important functional role of both the right and the left IFC in processing vocal emotions. Second, besides a supposed predominant role of the IFC for an attentive processing and evaluation of emotional voices in IFC, these recent studies also point to a possible role of the IFC in preattentive and implicit processing of vocal emotions. The studies specifically provide evidence that both the right and the left IFC show a similar anterior-to-posterior gradient of functional activity in response to emotional vocalizations. This bilateral IFC gradient depends both on the nature or medium of emotional vocalizations (emotional prosody versus nonverbal expressions) and on the level of attentive processing (explicit versus implicit processing), closely resembling the distribution of terminal regions of distinct auditory pathways, which provide either global or dynamic acoustic information. Here we suggest a functional distribution in which several IFC subregions process different acoustic information conveyed by emotional vocalizations. Although the rostro-ventral IFC might categorize emotional vocalizations, the caudo-dorsal IFC might be specifically sensitive to their temporal features.