Anatomo-functional organization of adaptive manual, orofacial and vocal control in the frontal cortex

This thesis primarily investigated how the human frontal cortex is organised to learn and use conditional rules linking contextual stimuli with manual, vocal and orofacial actions. My first study demonstrated that in humans: 1) the posterior lateral frontal cortex (pLFC) is organized along a dorso-ventral gradient, where the dorsal premotor cortex and ventral area 44 are involved in manual and vocal-orofacial conditional associations respectively, and 2) the anterior-most cingulate motor area (RCZa) within the mid-cingulate cortex (MCC), contributes to the evaluation of auditory feedback during the trial-and-error learning of the conditional associations. My second study showed that within the MCC, the three CMAs are functionally coupled with the lateral frontal cortex along a rostral-caudal gradient where more rostral regions are implicated in more abstracted levels of behavioral control. These findings provided important contributions to current theories about frontal cortical organization for behavioural control. Lastly, through an extensive review, I revealed that, within the pLFC-MCC network, area 44 and RCZa are part of a homologous brain network that might play a similar role in cognitive vocal/orofacial control across primates. My hypothesized role of this network in the adaptive control of vocal/orofacial actions based on auditory feedback monitoring had been validated, in humans, from my first study. Thus, my thesis had also revealed an important starting point - the area 44-RCZa, for future investigations into the potential neural changes that occurred across primate evolution to support the emergence of human speech abilities.