Disrupting inferior frontal cortex activity alters affect decoding efficiency from clear but not from ambiguous affective speech

Abstract

The evaluation of socio-affective sound information is accomplished by the primate neural auditory cortex in collaboration with limbic and inferior frontal brain nodes. For the latter, activity in inferior frontal cortex (IFC) is often observed during classification of voice sounds, especially if they carry affective information. Partly opposing views have been proposed, with IFC either coding cognitive processing challenges in case of sensory ambiguity or representing categorical object and affect information for clear vocalizations. Here, we presented clear and ambiguous affective speech to two groups of human participants during neuroimaging, while in one group we inhibited right IFC activity with transcranial magnetic stimulation (TMS) prior to brain scanning. Inhibition of IFC activity led to partly faster affective decisions, more accurate choice probabilities and reduced auditory cortical activity for clear affective speech, while fronto-limbic connectivity increased for clear vocalizations. This indicates that IFC inhibition might lead to a more intuitive and efficient processing of affect information in voices. Contrarily, normal IFC activity might represent a more deliberate form of affective sound processing (i.e., enforcing cognitive analysis) that flags categorial sound decisions with precaution (i.e., representation of categorial uncertainty). This would point to an intermediate functional property of the IFC between previously assumed mechanisms.TeaserInferior frontal cortex enforces cognitive analyses during affect decisions with different levels of sensory ambiguity.

Frontal mechanisms underlying primate calls recognition by humans

“…Causal links between IFG tri functioning and emotion recognition were also revealed in the literature (54). Noteworthy is the fact that activity in the left IFG tri also translates a level of uncertainty when decisional processes occur (53,(55)(56)(57). Combining our behavioural and neuroimaging results, it seems extremely plausible that decisional uncertainty was peaking when human participants were categorizing non-human primate vocalizations.…”