Impulsivity and compulsivity represent complementary cases of dysexecutive control, of considerable relevance to psychiatry. Whilst there has been intense focus on the dimensional construct of impulsivity, compulsivity has received far less attention. A working definition of compulsivity is of actions persisting inappropriate to the situation, having no obvious relationship to the ultimate goal and often resulting in undesirable consequences. This definition can be dissected neuropsychologically in several ways which I will illustrate by describing behavioural, computational and neuroimaging studies in two prototypical and devastating disorders of compulsivity, stimulant drug addiction and obsessive-compulsive disorder (OCD). One notion is that compulsive behavior is uncontrolled and excessive habitual responding at the expense of adaptive goal-seeking behaviour. Habits are governed by stimulus-response representations that do not involve goals or rewards. These two forms of behavioural control have been characterized by studies in experimental animals and humans indicating mediation by distinct, though interactive, fronto-striatal systems. Hypothetically, addiction and OCD represent imbalance in these neural systems for goal-directed and habitual behaviour. I will examine several different ways of testing this hypothesis in stimulant drug abusers and patients with OCD and make comparisons indicating common, as well as distinctive, features of the two disorders. I will explore the implications of this research for causal accounts of behaviour including psychopathology, new therapeutic approaches, and the functional organization of fronto-striatal systems in the brain and their chemical neuromodulation.
Everitt, B.J. & Robbins, T.W. (2016) Drug Addiction: Updating Actions to Habits to Compulsions Ten Years On. Annual Review of Psychology, 67, 23-50.
Gillan, C.M., Robbins, T.W. (2014) Goal-directed learning and obsessive-compulsive disorder. Philosophical Transactions of the Royal Society of London. Series B, Biological Sciences, 369(1655). pii: 20130475.