Dysphoria Clinical Trial
An fMRI Investigation Into the Effects of Transcranial Direct Current Stimulation on Reward Learning in Subclinical Depression.
|Source||University of Oxford|
|Contact||Margot J Overman, MSc|
|Phone||+44 (0) 1865 611455|
|Start date||February 2, 2018|
|Completion date||November 6, 2019|
The investigators are interested in investigating whether transcranial direct current stimulation (tDCS0 over the dorsolateral prefrontal cortex (DLPFC) can alter behaviour and neural activity in subclinical depression. tDCS is a neuromodulation technique that uses weak electrical current to increase (anodal stimulation) or decrease (cathodal stimulation) the probability of brain activity in the stimulated region. A growing body of evidence indicates that repeated administration of prefrontal tDCS can ameliorate symptoms of depression. A main characteristic of depression is that patients show a bias towards processing negative relative to positive information. Previously, we have demonstrated that a single session of prefrontal tDCS was associated with an increased learning rate for positive information in healthy adults. Here, the researchers will examine whether similar behavioural effects are found in individuals with subclinical depression when applying prefrontal tDCS. In addition, investigators will use neuroimaging measures to investigate how tDCS affects neural activity during a reward-learning task. The findings of the study will contribute to the understanding of the cognitive and neural effects of prefrontal tDCS in subclinical depression. It is predicted that tDCS will increase learning rates for positive information by altering activity in the prefrontal cortex and anterior cingulate cortex. The ultimate aim, to be explored through further studies, is to understand and improve how tDCS might be used in the treatment of depressive disorders.
Depression is a psychiatric illness characterised by a persistent bias towards processing
negative information. In a proof-of-concept study, the researchers demonstrated that
transcranial direct current stimulation (tDCS) increased learning rates for positive outcomes
in an information bias task in healthy adults. Here, the investigators aim to investigate
whether these findings of enhanced reward learning with tDCS extend to individuals with
subclinical depression. If changes in reward learning are found in this population, the
researchers will then investigate effects of tDCS on underlying neural processes associated
with the behavioural changes using MRI scanning. The study involves online screening, a
face-to-face screening session, two tDCS sessions, and potential MRI scanning sessions.
Screening: Participants will be asked to fill out a pre-screening online depression questionnaire (BDI) and will be asked questions regarding potential contraindications for tDCS/MRI. Participants with a BDI score of ≥10 are invited to a 1-hour screening session. Here, the participant will go through the procedures of the study with the researcher and will be asked to provide written informed consent. Subsequently, the SCID will be administered and tDCS/MRI screening forms to assess contraindications to brain stimulation and brain imaging will be completed by the researcher. If there are no contraindications to tDCS/MRI and no indications of current or history of psychological disorders, the researcher will schedule two tDCS testing sessions.
Testing sessions: Participants will be asked to fill out mood and anxiety questionnaires before and after the tDCS procedure. The researcher will explain the computerised task, and the participant will get the opportunity to practice the task. The researcher will then set up the tDCS equipment with the anode over the left dorsolateral prefrontal cortex (DLPFC) and the cathode over the right DLPFC. The researcher will briefly test the tDCS to ensure that the participant is comfortable with the stimulation. The participant will perform one block of the task without tDCS, followed by 20 minutes of tDCS at 2 mA while performing the decision-making task. Finally, the participant will be asked to perform additional task blocks without tDCS to investigate after-effects of the stimulation. If findings from these sessions indicate that tDCS can modulate reward learning in individuals with subclinical depression, participants will then be invited to take part in two additional MRI scanning sessions. If the findings indicate that tDCS can modulate reward learning in this population, participants will be invited to take part in two additional MRI scanning sessions.
Scanning sessions: Participant will be familiarised with the MRI environment and will be given the opportunity to practice the computerised task. Then, participants will be asked to fill out mood and anxiety questionnaires. The researcher will set up the tDCS equipment. The participant will enter the MRI scanner and will perform one block of the practiced task. Subsequently, tDCS will be applied for 20 minutes whilst participants perform additional blocks of the decision-making task in the scanner. In one of the sessions, participants will receive active tDCS, whereas in the other session they will receive sham tDCS. Following the stimulation, the participant may be asked to complete another block of the decision-making task in the scanner. In addition, the participant will undergo DTI and spectroscopy scans. After scanning, the participant will again be asked to complete the mood and anxiety questionnaires. Furthermore, they may be asked to perform an emotional processing task of face recognition.