P300 event-related potential in euthymic patients with bipolar disorder

The P300 event-related potential in bipolar disorder: A systematic review and meta-analysis

BACKGROUND

Neurophysiology including P300, that is a typical index of event-related potential, may be potential biomarkers for bipolar disorder (BD) and it can be useful towards elucidating the pathophysiology of BD. However, previous findings from P300 studies were inconsistent due to the heterogeneity of research methods, which make it difficult to understand the neurobiological significance of them. The aim of this study is to conduct a meta-analysis on P300 in patients with BD.

METHOD

A literature search was conducted using PubMed to identify studies that compared P300 event-related potential between patients with BD and healthy controls (HCs). We analyzed P300 indices such as amplitude and latency of P3a and P3b in auditory or visual paradigms. Further, moderator analyses were conducted to investigate the influence of patient characteristics (i.e. history of psychosis, diagnostic subcategories [BD-I/BD-II], and phase of illness [euthymic, manic, or depressive]) on P300 indices.

RESULT

Out of 124 initial records, we included 30 articles (BD: N = 1331; HCs: N = 1818). Patients with BD showed reduced P3a and P3b amplitude in both paradigms and delayed P3b latency in auditory paradigms compared to HCs. There was no influence on the history of psychosis, diagnostic subcategories, or phase of illness on P300 indices.

LIMITATION

The difference in medication use was difficult to control and it may affect the results.

CONCLUSION

This meta-analysis provides evidence for P300 abnormalities in patients with BD compared to HCs. Our results suggest that P300 may be trait markers rather than state markers in this illness.

Auditory P300 study in patients with convalescent bipolar depression and bipolar depression

The aim of this study was to investigate the information-processing changes during an auditory oddball task among healthy controls (HCs), convalescent bipolar depression (BPC), and bipolar depression (BPD) patients. Thirty patients with BPD, 27 patients with BPC, and 30 HC were recruited in this study. The participants' performance (reaction time and accuracy) as well as P300 amplitude and latency during the tests were analyzed statistically. BPD and BPC showed poor task performance compared with HC. BPD had lower P300 amplitude and delayed P300 latency in the frontal, central, and parietal areas than HC. BPC had lower P300 amplitude, but no difference in P300 latency compared with the HC group. Further, P300 latency was significantly delayed over the right relative to the left region. In conclusion, bipolar patients had P300 abnormalities and deficits in cognitive processing of stimulus, and may be present even when emotional symptoms were relieved.

Inhibitory control in euthymic bipolar disorder: Event related potentials during a Go/NoGo task

OBJECTIVES

Patients with bipolar disorder (BD) are reported to have difficulties with inhibition, even in a euthymic state. However, the literature on cortical activity associated with response inhibition in BD remains ambiguous. This study investigates inhibition in euthymic BD using electrophysiological measures, while controlling for effects of specific medications.

METHODS

Twenty patients with BD were compared with eighteen healthy controls on a Go/NoGo task while electroencephalogram was recorded. Behavioral and event-related potential (ERP) measurements were analyzed for the two groups. Medication effects were controlled for in the analysis.

RESULTS

Patients with BD had marginally reduced NoGo N2 amplitudes and increased NoGo P3 amplitudes compared with healthy controls when patients using benzodiazepines were excluded from the study. No behavioral differences between the groups were found.

CONCLUSIONS

Reduced NoGo N2 amplitudes in BD reflect aberrant conflict detection, an early stage of the inhibition process. In addition, increased NoGo P3 amplitudes in BD despite normal task performance reflect an overactive cortical system during a simple inhibition task.

SIGNIFICANCE

Difficulties in early stages of inhibition in BD appear to have been compensated by increased cortical activation. This study extends current knowledge regarding cortical activations relating to inhibition in BD.

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.

Physiological Correlates of Bipolar Spectrum Disorders and their Treatment

Bipolar spectrum disorders (BSDs) are associated with great personal and socioeconomic burden, with patients often facing a delay in detection, misdiagnosis when detected, and a trial-and-error approach to finding the most appropriate treatment. Therefore, improvement in the assessment and management of patients with BSDs is critical. Should valid physiological measures for BSDs be identified and implemented, significant clinical improvements are likely to be realized. This chapter reviews the physiological correlates of BSDs and treatment, and in doing so, examines the neuroimaging, electroencephalogram, and event-related potential, and peripheral physiological correlates that both characterize and differentiate BSDs and their response to treatment. Key correlates of BSDs involve underlying disturbances in prefrontal and limbic network neural activity, early neural processing, and within the autonomic nervous system. These changes appear to be mood-related and can be normalized with treatment. We adopt an "embodied" perspective and propose a novel, working framework that takes into account embodied psychophysiological mechanisms in which the physiological correlates of BSD are integrated. This approach may in time provide the objective physiological measures needed to improve assessment and decision making when treating patients with BSDs. Future research with integrative, multimodal measures is likely to yield potential applications for physiological measures of BSD that correlate closely with diagnosis and treatment.

Mindfulness based cognitive therapy improves frontal control in bipolar disorder: a pilot EEG study

BACKGROUND

Cognitive processing in Bipolar Disorder is characterized by a number of attentional abnormalities. Mindfulness Based Cognitive Therapy combines mindfulness meditation, a form of attentional training, along with aspects of cognitive therapy, and may improve attentional dysfunction in bipolar disorder patients.

METHODS

12 euthymic BD patients and 9 control participants underwent record of electroencephalography (EEG, band frequency analysis) during resting states (eyes open, eyes closed) and during the completion of a continuous performance task (A-X version, EEG event-related potential (ERP) wave component analysis). The individuals with BD completed an 8-week MBCT intervention and record of EEG was repeated.

RESULTS

(1) Brain activity, individuals with BD showed significantly decreased theta band power, increased beta band power, and decreased theta/beta ratios during the resting state, eyes closed, for frontal and cingulate cortices. Post MBCT intervention improvement over the right frontal cortex was seen in the individuals with BD, as beta band power decreased. (2) Brain activation, individuals with BD showed a significant P300-like wave form over the frontal cortex during the cue. Post MBCT intervention the P300-like waveform was significantly attenuated over the frontal cortex.

CONCLUSIONS

Individuals with BD show decreased attentional readiness and activation of non-relevant information processing during attentional processes. These data are the first that show, MBCT in BD improved attentional readiness, and attenuated activation of non-relevant information processing during attentional processes.

Genetics and intermediate phenotypes of the schizophrenia--bipolar disorder boundary

Categorization of psychotic illnesses into schizophrenic and affective psychoses remains an ongoing controversy. Although Kraepelinian subtyping of psychosis was historically beneficial, modern genetic and neurophysiological studies do not support dichotomous conceptualization of psychosis. Evidence suggests that schizophrenia and bipolar disorder rather present a clinical continuum with partially overlapping symptom dimensions, neurophysiology, genetics and treatment responses. Recent large scale genetic studies have produced inconsistent findings and exposed an urgent need for re-thinking phenomenology-based approach in psychiatric research. Epidemiological, linkage and molecular genetic studies, as well as studies in intermediate phenotypes (neurocognitive, neurophysiological and anatomical imaging) in schizophrenia and bipolar disorders are reviewed in order to support a dimensional conceptualization of psychosis. Overlapping and unique genetic and intermediate phenotypic signatures of the two psychoses are comprehensively recapitulated. Alternative strategies which may be implicated into genetic research are discussed.