This study will generate new information on how to optimise brain targets with ECT stimulation.

This study will differentiate the brain regions which are related to the effectiveness of electroconvulsive therapy (ECT) as a treatment, from the brain regions associated with memory impairment, with ECT stimulation. This will be done by 1) testing effects on memory of 4 different forms of ECT, which stimulate the brain differently; 2) in a subset of participants, use computer modelling to assess the pattern of brain stimulation with the 4 forms of ECT, and match these results to memory outcomes.

Inclusion Criteria:

• Aged ≥18 years; right-handed
• DSM-5 Major Depressive Episode
• Prescribed with a course of ECT

Exclusion Criteria:

• Diagnosis (as defined by DSM-V) of psychotic disorder (apart from Major Depressive Episode with Psychotic features), current drug or alcohol abuse or dependence;
• ECT treatments in last 3 months from a prior course of ECT;
• Score <23 on the Montreal Cognitive Assessment Battery (MoCA);
• Past or current neurological illness or injury, medical illness which may significantly affect neuropsychological function;
• Inability to give informed consent or comply with study procedures; or
• Not having worked or studied in an English speaking background (to ensure validity of neuropsychological testing).
• Not be claustrophobic (if having an MRI brain scan).
• Not have any metal in your head or body (if having an MRI brain scan).
• Likely non response to RUL forms of ECT, as indicated by past non response to RUL ECT

Both participants and the outcome assessor will be blinded.