Body-brain interface in the primate insular cortex

The anterior insular cortex recently emerged as having a crucial role in engendering subjective feelings and has the potential to contribute to awareness. Our lab combines neuroanatomical, functional (fMRI, ePhys, optogenetics) and comparative methods to examine the organization of the insula in macaque monkeys and humans. We demonstrated that each of the three classical architectonic sectors of the insula (agranular, dysgranular, granular) in macaques is divided into distinct and sharply delimited areas and sub-areas. Using tract-tracing, we showed that each of these modules has specific and equally sharply delimited sets of neuronal connections. A detailed mapping of these connections combined with fMRI and electrophysiological investigations of the interotopic map of the insula has led to the development of a working model of the insula in which primary interoceptive afferents in the dorsal fundus of the insula are progressively integrated with ‘personal’ proprioceptive and ‘social’ audio-visual activities in distinct dysgranular areas, and with further visceromotor/sensory representations in the anterior agranular insula. We showed that one of the agranular areas specifically contains the von Economo neuron (VEN) and fork neuron (FN). We showed that both neurons project to subcortical homeostatic centers. Using fMRI combined with direct electrical stimulation (DES-fMRI) or neural event triggering based on specific LFP events (NET-fMRI) in the left and right VEN-area, we unveiled markedly asymmetric whole-brain activation patterns that could underlie the differential influence of the left and right anterior insula over brain and bodily states.