Opening new vistas on obsessive-compulsive disorder with the observing response task

Abstract

Obsessive-compulsive disorder (OCD), a highly prevalent and debilitating disorder, is incompletely understood in terms of underpinning behavioural, psychological, and neural mechanisms. This is attributable to high symptomatic heterogeneity; cardinal features comprise obsessions and compulsions, including clinical subcategories. While obsessive and intrusive thoughts are arguably unique to humans, dysfunctional behaviours analogous to those seen in clinical OCD have been examined in nonhuman animals. Genetic, ethological, pharmacological, and neurobehavioural approaches all contribute to understanding the emergence and persistence of compulsive behaviour. One behaviour of particular interest is maladaptive checking, whereby human patients excessively perform checking rituals despite these serving no purpose. Dysfunctional and excessive checking is the most common symptom associated with OCD and can be readily operationalised in rodents. This review considers animal models of OCD, the neural circuitries associated with impairments in habit-based and goal-directed behaviour, and how these may link to the compulsions observed in OCD. We further review the Observing Response Task (ORT), an appetitive instrumental learning procedure that distinguishes between functional and dysfunctional checking, with translational application in humans and rodents. By shedding light on the psychological and neural bases of compulsive-like checking, the ORT has potential to offer translational insights into the underlying mechanisms of OCD, in addition to being a platform for testing psychological and neurochemical treatment approaches.

Keywords: Animal models; Checking; Obsessive-compulsive disorder.

Fig. 1

Observing Response Task for rats (left) and humans (right). The task is conducted in operant chambers for rats and on a computer screen with a keyboard for humans. (A) Basic task schedule. Two response manipulanda are presented, and pressing (red arrows/pointing) on one of these is deemed a correct response and rewarded with a sucrose pellet for the rats, and the presentation of a pleasant noise and points for the humans. The correct response changes throughout the session (yellow arrow). (B) The currently correct response can be indicated through making a functional checking response. For the rats, the checking lever is presented on the back of the chamber. For the humans, a checking key is available. (C) Pressing the observing lever illuminates a cue light above the currently correct lever for the rats, and the presentation of a light blue cue square behind the currently correct symbol for the humans. As these responses provide information, they are deemed “functional” observing responses. Responding on the correct manipulandum will be rewarded for as long as that response is correct, regardless of whether the cue is still presented. (D) Pressing of the observing lever or key while the cue is still present provides no information and is deemed a “dysfunctional” observing response.