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International audience; Neuroimaging studies of patients with treatment-resistant depression (TRD) have reported abnormalities in frontal and temporal regions. We sought to determine whether metabolism in those regions might be related to response to repetitive transcranial magnetic stimulation (TMS) in patients with TRD. Magnetic resonance images and baseline resting-state cerebral glucose uptake index (gluMI) obtained using 18F-fluorodeoxyglucose positron emission tomography were analyzed in TRD patients who had participated in a double-blind, randomized, sham-controlled trial of prefrontal 10Hz-TMS. Among the patients randomized to active TMS, 17 responders, defined as having 50% depression score decrease, and 14 nonresponders were investigated for pre-stimulation glucose metabolism and compared with 39 healthy subjects using a voxel-based analysis. In nonresponders relative to responders, gluMI was lower in left lateral orbitofrontal cortex (OFC), and higher in left amygdala and uncinate fasciculus. OFC and amygdala gluMI negatively correlated in nonresponders, positively correlated in responders, and did not correlate in healthy subjects. Relative to healthy subjects, both responders and nonresponders displayed lower gluMI in right dorsolateral prefrontal (DLPFC), right anterior cingulate (ACC), and left ventrolateral prefrontal, cortices. Additionally, nonresponders had lower gluMI in left DLPFC, ACC, left and right insula, and higher gluMI in left amygdala and uncus. Hypometabolisms were partly explained by gray matter reductions, while hypermetabolisms were unrelated to structural changes. The findings suggest that different patterns of frontal-temporal limbic abnormalities may distinguish responders and nonresponders to prefrontal magnetic stimulation. Both preserved OFC volume and amygdala metabolism might precondition response to TMS.

International audience; Cocaine addiction is often modeled in experimental paradigms where rodents learn to self-administer the drug. However, the extent to which these models replicate the functional alterations observed in clinical neuroimaging studies of cocaine addiction remains unknown. We used Magnetic Resonance Imaging (MRI) to assess basal and evoked brain function in rats subjected to a prolonged, extended-access cocaine self-administration scheme. Specifically, we measured basal cerebral blood volume (bCBV), an established correlate of basal metabolism, and assessed the reactivity of the dopaminergic system by mapping the pharmacological MRI (phMRI) response evoked by the dopamine-releaser amphetamine. Cocaine-exposed subjects exhibited reduced bCBV in fronto-cortical areas, nucleus accumbens, ventral hippocampus and thalamus. The cocaine group also showed an attenuated functional response to amphetamine in ventro-striatal areas, an effect that was significantly correlated with total cocaine intake. An inverse relationship between bCBV in the reticular thalamus and the frontal response elicited by amphetamine was found in control subjects but not in the cocaine group, suggesting that the inhibitory interplay within this attentional circuit may be compromised by the drug. Importantly, histopathological analysis did not reveal significant alterations of the microvascular bed in the brain of cocaine-exposed subjects, suggesting that the imaging findings cannot be merely ascribed to cocaine-induced vascular damage. These results document that chronic, extended-access cocaine SA in the rat produces focal fronto-cortical and striatal alterations that serve as plausible neuro-biological substrate for the behavioral expression of compulsive drug-intake in laboratory animals.