Major depressive disorder is associated with dysfunctional motivation, reward and cognitive processing. A clinical feature of depression is low motivation but it remains unclear whether this reflects a fundamental impairment in basic incentive motivation or a higher level deficit in integrating cognitive and emotional information in complex situations. The focus of this thesis was to investigate the behavioural and neural bases underlying the processing of reward-related and motivational processes in major depression; in particular, the influence of variable reward magnitudes on incentive motivation and the interaction between information processing and response to reinforcement.