In this presentation, I present some recent findings from my SSA-funded PhD project. One of my studies was exploring -for the first time- the integrity of the insular cortex in social drinkers, using magnetic resonance spectroscopy, voxel and surface-based morphometry.
The insula is usually referred to as an interoceptive hub which integrates physiological inputs in representation of bodily responses and subjective feeling states. In the last decade, a growing body of evidence highlighted the role of the insular cortex in drug seeking behaviour. At the neurochemical level, alcohol is known to interact with the glutamatergic neurotransmission; leading to neuronal death and cerebral atrophy. Thirty-two healthy male social drinkers filled questionnaires related to severity of alcohol intake, craving and interoceptive sensitivity. Insular glutamate plus Glutamine (Glx) and total N-acetylaspartate plus N-acetyl-aspar-tylglutamate (TNAA) concentrations were measured from a voxel placed in the right mid-insula, using magnetic resonance spectroscopy (MRS). Whole brain as well as region of interest analyses (right insula) were run to evaluate the relationship between psychometric measures, volume and surface parameters.
Social drinking was related to a reduction of insular Glx concentration and to a decreased insular gyrification. Increased insular tNAA concentration and increased insular gyrification were observed in participants with high interoceptive sensitivity. Moreover, subjective rating of craving was positively correlated with increased grey matter in the dorsal striatum. This study is, to date, the first study to explore the neurochemical and morphological integrity of the insular cortex in social drinkers. Together, these data reveal a modulation of insular glutamate plus glutamine concentration as well as a modulation of brain volume and surface parameters by alcohol use. These abnormalities may lead to loss of control over alcohol and shift to compulsive drinking. Further (longitudinal) studies should explore the evolution of interoceptive processes through the different stages of alcohol and drug development.