Brain Glucose Metabolism in Healthy Subjects and Depressive Patients During Transcranial Direct Current Stimulation

With this study, we will be able to substantiate if regional and whole brain glucose metabolism is affected by tDCS, assess the amount of signal change in relation to different currents and measure differences in glucose metabolism under stimulation reactivity between healthy subjects and depressive patients. The objective is to investigate the changes of regional cerebral metabolic rate of glucose (rCMRglu) in the brain after transcranial direct current stimulation in healthy subjects and depressive patients. The design is a cross-sectional proof of principle study in 20 healthy subjects and 20 depressed patients. During the PET scan tDCS will be applied with varying stimulus intensity. Furthermore, subjects will undergo a second PET scan with single-blind sham stimulation in order to validate the effects of tDCS. rCMRglu will be quantified using voxel-wise and ROI-based approaches. Changes in rCMRglu associated with tDCS-application will be calculated with a general linear model in a ramp function of the task-specific glucose uptake, according to previous work in our group. Exploratory statistical testing will be done using a paired samples t-test between task and rest conditions.