Abstract
Little is known about the functional anatomy of the insula. Several experimental data suggest that the organization of the insular connections from the different insular cytoarchitectonic regions is related to different functional domains within the insula, and recent electrophysiological and neuroimaging studies have shown the existence of an anterior-posterior organization within the insular cortex. To further investigate this point, we carried out a positron emission tomography (PET) study using fluorodeoxyglucose (18F-FDG) in patients with medial temporal lobe epilepsy who experienced emotional or visceral symptoms that are supposed to be elicited in the insula. The aim of our study was to assess the existence of a functional insular somatotopic organization. FDG-PET studies were carried out in 18 epileptic patients. Data were analyzed using statistical parametric mapping (SPM96). The results showed that the emotional symptoms were correlated with hypometabolism in the anterior part of the ipsilateral insular cortex, while visceral symptoms were correlated with hypometabolism in the posterior part (p=0.001). This neuroimaging study demonstrates that the anterior part of the insular cortex corresponding to the agranular cortex subserves emotional functions while the posterior part of the insular cortex corresponding to the granular cortex subserves ascending visceral symptoms.
Résumé
L'anatomie fonctionnelle de l'insula demeure mal connue. Les données expérimentales suggèrent que l'organisation fonctionnelle de l'insula est en rapport avec son organisation cytoarchitectonique et ses connexions réciproques avec les différentes régions cérébrales. Des études électrophysiologiques et de neuro-imagerie récentes ont montré l'existence d'une organisation somatotopique au sein de l'insula avec un gradient antéro-postérieur. Pour préciser ce dernier point, nous avons conduit une étude en tomographie par émission de positons utilisant le fluorodésoxyglucose (18F-FDG) comme traceur. Cette étude a été menée chez dix-huit patients souffrant d'une épilepsie de la face médiale du lobe temporal et présentant des symptômes émotionnels ou viscéraux liés à une propagation insulaire de la décharge épileptique. Le but de l'étude était de prouver l'existence d'une organisation somatotopique fonctionnelle au sein de l'insula. Les résultats ont montré que les symptômes émotionnels étaient corrélés à un hypométabolisme situé dans la région antérieure de l'insula alors que les symptômes viscéraux étaient corrélés à un hypométabolisme situé dans la région postérieure de l'insula (p=0,001). Cette étude de neuro-imagerie fonctionnelle démontre donc que le cortex insulaire agranulaire ventral sous-tend des fonctions émotionnelles alors que le cortex granulaire dorsal sous-tend des fonctions viscérales.
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Dupont, S., Bouilleret, V., Hasboun, D. et al. Functional anatomy of the insula: new insights from imaging. Surg Radiol Anat 25, 113–119 (2003). https://doi.org/10.1007/s00276-003-0103-4
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DOI: https://doi.org/10.1007/s00276-003-0103-4