Multiple routes of communication within the amygdala-mPFC network: A comparative approach in humans and macaques.

The network formed by the amygdala (AMG) and the medial Prefrontal Cortex (mPFC), at the interface between our internal and external environment, has been shown to support some important aspects of behavioral adaptation. Whether and how the anatomo-functional organization of this network evolved across primates remains unclear. Here, we compared AMG nuclei morphological characteristics and their functional connectivity with the mPFC in humans and macaques to identify potential homologies and differences between these species. Based on selected studies, we highlight two subsystems within the AMG-mPFC circuits, likely involved in distinct temporal dynamics of integration during behavioral adaptation. We also show that whereas the mPFC displays a large expansion but a preserved intrinsic anatomo-functional organization, the AMG displays a volume reduction and morphological changes related to specific nuclei. We discuss potential commonalities and differences in the dialogue between AMG nuclei and mPFC in humans and macaques based on available data.

Response selection versus feedback analysis in conditional visuo-motor learning.

Conditional associative sensori-motor learning (i.e. the acquisition of specific arbitrary sensori-motor mappings) involves several processes that depend upon the integrity of the fronto-striatal system. The specific role of the different components of the fronto-striatal system in this type of learning is still unclear and was examined in the present functional Magnetic Resonance Imaging (fMRI) study in humans. The subjects had to learn by trial and error arbitrary associations between visual stimuli and motor responses in an experimental paradigm designed to dissociate between the neuronal substrates specifically involved in the selection of the appropriate response and in the analysis of the feedback obtained during the learning and post-learning periods. First, the results demonstrate that the dorsal premotor (PMd) cortex is the critical structure for the acquisition and execution of arbitrary mappings of visual stimuli to motor responses. Second, they reveal an important shift in activation from the cognitive fronto-striatal network (involving the caudate nucleus, the dorsolateral prefrontal cortex, and the PMd) to the motor fronto-striatal network (involving the putamen and the PMd) as we move from initial learning of sensori-motor relations to the post-learning selection of the responses. Finally, they show that feedback processing, but not response selection, increased activity in the anterior cingulate and orbitofrontal cortical regions, demonstrating the selective involvement of these limbic frontal regions in the processing of the consequences of a given action. Altogether our data suggest that, in conditional visuo-motor learning, the associations are critically regulated by the dorsal premotor cortex and the striatum, with additional brain areas contributing to specific aspects of the learning and performance of such associations.