Hidden beneath the surface of bipolar disorder: cognitive processes underlying movement
6 November 2018
UAntwerp - Campus Drie Eiken - Building Q - Promotiezaal - Universiteitsplein 1 - 2610 WILRIJK (route: UAntwerpen, Campus Drie Eiken
Prof M. Morrens, Prof M. Dhar & Prof B. Sabbe
PhD defence Anne Morsel - Faculty of Medicine and Health Sciences
Abstract (Presentation in English)
Apart from mood episodes, cognitive and psychomotor abnormalities are prominent clinical features of bipolar disorder (BD). These deficits persist in euthymia and interfere with daily functioning of the individuals, thereby making them important targets for treatment. ‘Psychomotor functioning’ refers to the contribution of all cognitive and motor processes involved in movements (from planning, initiation, execution and cognitive control), whereby dysfunction at any stage can result in disturbed psychomotor functioning. The aim of the research was to conduct an in-depth investigation of underlying mechanisms and cognitive sub-processes relating to psychomotor abnormalities in euthymic BD, where research has been lacking.
To investigate psychomotor speed in euthymic BD, drawing tasks were performed using a digitized writing tablet. This method enabled motor and cognitive sub-processes involved in movements to be measured. Individuals with BD in a euthymic demonstrated slowing of cognitive processes relating to movement, while neuro-motor processes were spared. To better understand neuro-cognitive processes underlying psychomotor behavior in BD, electrophysiological measures were used. Two cognitive control processes necessary for successful movements were investigated; inhibition of unwanted behavioral output and performance monitoring, a process of continuously monitoring behaviour and making subsequent changes following an error. Using a Go/NoGo task, individuals with BD demonstrated normal inhibitory behavior together with abnormal electrophysiological activity. Specifically, individuals with BD had marginally reduced NoGo N2 amplitudes, an event-related potential (ERP) measure of conflict detection (generated in the anterior cingulate cortex (ACC) and inferior frontal cortex) and increased NoGo P3 amplitudes, indicating an over-activation of cortical activity when inhibition is necessary. In other words, difficulties in early stages of inhibition in BD may be compensated by increased cortical activation. In addition, using a Flankers task reduced Error-Related Negativity (ERN) amplitudes were demonstrated in BD, an ERP generated in the ACC during the production of errors, reflecting reduced performance monitoring in BD.
Results of the research extend knowledge relating to underlying neurobiological processes relating to psychomotor dysfunction in BD, specifically reduced ACC activation and increased cortical activity implicating an abnormal cognitive control circuit in BD. In addition, results extend knowledge relating to information processing capacities in BD whereby equal performance in BD requires more effort. Due to these underlying neurobiological abnormalities, psychomotor difficulties may be apparent in complex real-life situations. Thus, in addition to attempting to stabilize mood in BD, more efforts should be aimed at treating cognitive deficits and their underlying neurobiological correlates, as it and may aid functional remission.