Characterizing cerebral metabolite profiles in anorexia and bulimia nervosa and their associations with habitual behavior
Background Anorexia nervosa (AN) and bulimia nervosa (BN) are associated with altered brain structure and function, as well as increased habitual behavior. This neurobehavioral profile may implicate neurochemical changes in the pathogenesis of these illnesses. Altered glutamate, myo -inositol and N- acetyl aspartate (NAA) concentrations are reported in restrictive AN, yet whether these extend to binge-eating disorders, or relate to habitual traits in affected individuals, remains unknown. Methods Using single-voxel proton magnetic resonance spectroscopy, we measured glutamate, myo -inositol and NAA in 85 women [n=22 AN (binge-eating/purging subtype; AN-BP), n=33 BN, n=30 controls]. Spectra were acquired from the right inferior lateral prefrontal cortex and the right occipital cortex. To index habitual behavior, participants performed an instrumental learning task and completed the Creature of Habit Scale. Exploratory analyses examined associations between metabolites and habitual behavior. Results Women with AN-BP, but not BN, had reduced myo-inositol and NAA concentrations relative to controls in both voxels. Patient groups had intact performance on the instrumental learning task; however, both groups reported increased routine behaviors compared to controls. Women with BN also reported greater automatic behaviors, and automaticity was related to reduced prefrontal glutamate and NAA in the AN-BP group. Discussion Findings: extend previous reports of reduced myo -inositol and NAA levels in AN to AN-BP, which may reflect disrupted axonal-glial signaling. Although we found inconsistent support for increased habitual behavior in AN-BP and BN, we identified preliminary associations between prefrontal metabolites and automaticity in AN-BP. These results provide further evidence of unique neurobiological profiles across binge-eating disorders.