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Cognitive control of vocalizations in the primate frontal cortex

On The May 30, 2016

Kep-kee Loh

Team Director - Emmanuel Procyk

Abstract :

Two main frontal brain regions have been commonly associated with human speech production: a ventrolateral frontal region (VLF; including the ventrolateral prefrontal cortex (Broca’s area) and the adjacent ventral premotor area) and a dorsomedial frontal region (DMF; that includes the mid-cingulate cortex (MCC), the pre-supplementary and supplementary areas). Interestingly, this VLF-DMF network is also associated with flexible vocal control in non-human primates (NHPs). As such, understanding the functioning of this network and how it might have changed across primate evolution could provide important insights into the emergence of modern human speech. At this juncture, the precise functional contributions of these regions to the cognitive control of vocalizations in both humans and NHPs remain poorly characterized. Existing literature have implicated the primate lateral frontal cortex in the conditional selection of motor responses via sensorimotor rules and the MCC in the evaluation of action outcomes for adapting future behaviors. As such, we hypothesize that the VLF is involved in the conditional selection of vocal/orofacial responses and that the MCC is involved in the evaluation of behavioral feedback to adapt vocal/orofacial responses. We tested these hypotheses in human subjects via a conditional associative learning task in which they first learnt conditional associations between visual stimuli and vocal/orofacial responses via trial-and-error, and subsequently performed the learnt associations. Congruent with our hypotheses, preliminary findings revealed that: 1) the VLF showed increased BOLD activity as subjects selected between vocal/orofacial responses based on the presented visual stimuli; while 2) the MCC showed increased activity as subjected processed auditory feedback during the trial-and-error learning of visuo-vocal/orofacial associations.