Attentional processes in the human insula

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The insula is one of the most enigmatic brain regions. Our understanding of its functions in humans mainly comes from non-invasive functional imaging techniques providing indirect markers of neural activity. Yet, the insula is regularly activated in studies using such neuroimaging techniques, no matter the sensory modality involved, which may be attributable to a role in multiple aspects of attention. Indeed, the insula is thought to be a key structure in multiple functional networks, including the salience network involved in the detection and filtering of salient stimuli. However, the specific role(s) played by the insula remains unclear, partly due to the low temporal resolution of traditional functional neuroimaging techniques, and because the rarity of brain lesions restricted to the insula has limited lesion studies to date. Our team was first recognized for its expertise in insular epilepsy and surgery. In rare specialized epilepsy centers such as ours, direct exploration of the insula using intracranial electrodes is regularly performed to better delineate the epileptic focus when non-invasive techniques cannot. These electrodes can be used to study information processing with very high spatial and temporal resolution. Furthermore, we have performed nearly 50 insular resections to cure drug-resistant epileptic patients at our epilepsy center since the last 15 years. Such resections limited to insular areas constitute an unprecedented opportunity to study insular functions in humans. Our prior experiments involving patients with invasive EEG (iEEG) recordings and who had insular resection allowed us to establish as leaders in insula research. We wish to pursue our exploration of the role and functions of the insula, notably in attentional processes using two different and complementary techniques. First, we will use iEEG recordings in epileptic patients performing attention tasks to study the spatio-temporal dynamics of information processing in the insula. Secondly, patients with insular resection will be assessed on different neurobehavioral tasks to study the specific role of the insula in attention performance. We expect our research proposal to impact neuroscience research by helping understand one of the least studied brain regions, and by contributing to a better understanding of attentional processes in humans.