Systematic review of cognitive event related potentials in euthymic bipolar disorder.

Cognitive deficits are critical features of bipolar disorder (BD), greatly impacting quality of life. The aim is to systematically review and critically evaluate underlying event related potential (ERP) features in euthymic BD relating to differences in sensory processes, attention, inhibition and conflict monitoring compared with healthy controls. 911 unique articles were identified using the PubMed database and 14 studies met the inclusion criteria. Individuals with BD in a euthymic state have reduced P50 sensory gating and reduced P100 amplitudes compared with healthy controls. Many studies demonstrated reduced P300 amplitudes and normal P300 latencies in BD. In addition, reduced NoGo N2 and abnormal NoGo P3 activity were observed in BD. Finally, there is some evidence of reduced error-related negativity amplitudes in BD. Importantly, ERP modulations vary with stimulus factors and clinical profile. The functional significance of these findings and clinical implications are discussed. ERP differences in BD arise at various stages of cognitive processing, specifically in early auditory and visual processing, attention allocation, context updating, inhibition and conflict monitoring. Treating these deficits and their underlying neurobiological disturbances corresponding to abnormal performance on cognitive tasks may aid functional remission. This knowledge might enable personalized treatment interventions targeting specific cognitive deficits.

Unraveling psychomotor slowing in bipolar disorder.

BACKGROUND/AIMS: In addition to affective and cognitive symptomatology, psychomotor deficits are known to be present in bipolar disorder (BD). Psychomotor functioning includes all of the processes necessary for completing a movement, from planning to initiation and execution. While these psychomotor symptoms have been studied extensively in schizophrenia and major depressive disorder, only simple measures have been conducted in BD. The present study examines psychomotor functioning in BD. METHODS: Twenty-two euthymic BD patients and 21 healthy controls performed three computerized copying tasks varying in cognitive load. Movement times (MT), reflecting fine motor processing, and initiation times (IT), reflecting cognitive processing of visual-spatial information, were separately measured in each group. RESULTS: The BD patients had longer IT but not MT in the simplest task and the opposite pattern of longer MT but not IT in the complex task. However, when controlling for residual mood symptoms, the MT were no longer significantly slower in the BD group. CONCLUSIONS: The longer MT and IT in BD reflect overall psychomotor slowing. Specifically, the results provide evidence for cognitive slowing in BD. In addition, the longer MT in the complex task reflect a slowed motor component of movement when the cognitive load is high and when depressive symptoms are present. These findings extend the current knowledge of the nature of psychomotor slowing in BD and may have important prognostic implications for patients.

Electrophysiological (EEG) evidence for reduced performance monitoring in euthymic bipolar disorder.

OBJECTIVES: Apart from mood episodes, many cognitive deficits are present in bipolar disorder (BD). Performance monitoring is an important aspect of executive functioning and involves continuous monitoring of behavior and making subsequent changes when an error is made. On a neurophysiological level, the error-related negativity (ERN), an event-related brain potential (ERP) generated in the anterior cingulate cortex (ACC), reflects this process of performance monitoring. Abnormal ERN amplitudes have been observed in many major psychiatric disorders. However, despite conflicting evidence regarding the role of the ACC in BD, no studies to date have investigated performance monitoring as reflected in the ERN in BD. METHODS: Sixteen patients with BD in a euthymic state and 14 matched healthy controls performed a speeded two-choice reaction-time paradigm (Flankers Task) while electroencephalogram (EEG) measures were obtained. Behavioral and ERP measurements were analyzed for the two groups. RESULTS: The patients with BD, although euthymic, scored higher on depressive symptoms than healthy controls. While no behavioral group differences were found, patients with BD displayed lower ERN amplitudes than healthy controls when controlling for effects of residual mood. CONCLUSIONS: The lower ERN amplitudes in the BD group reflect reduced performance monitoring and extend current knowledge of executive functioning in BD. Importantly, these findings go a long way to resolving the contradictory results regarding ACC involvement in BD by showing that taking into account residual mood may greatly influence error-related ACC activations and is critically important in understanding cognitive deficits in BD.