Neuropsychological and Neurophysiological Assessment in Different Phases of Bipolar Disorder

Recent studies have shown that cognitive deficits are significant and pervasive even among remitted bipolar disorder patients. The aim of the current controlled study was to investigate the relationships between cognitive performances, symptom severity, and event-related potentials with regard to different episodes in bipolar patients.

This study was conducted on a total of 60 patients diagnosed with bipolar disorder (20 depressive, 20 manic, and 20 in remission). The Frontal Assessment Battery and Stroop test were used for neuropsychological assessment. Event-related potentials were measured using frontal, central, and parietal EEG recordings, while Nihon-Kohden EMG-EP system was used.

Delayed P300 latencies were observed in all phases of bipolar disorder when compared to the controls. There was a positive relationship between frontal, central P300 latencies, and Young Mania Rating Scale scores. A strong positive relationship was also observed between Young Mania Rating Scale scores and Stroop interference scores. A negative relationship was observed between Frontal Assessment Battery scores and frontal, central, and parietal N100 latencies and amplitudes in depressed patients. Consistent with these findings, there was a relationship between Hamilton Depression Rating Scale scores and N100 latencies. There was also a positive relationship between Stroop interference scores and central N200 latency, as well as frontal N200 and parietal N200 amplitudes, while a negative relationship was observed between Stroop total time scores and central N200 latency as well as parietal N200 amplitude in depressed patients.

Study findings imply that depression episodes could be associated with decision-making autonomy and memory issues, while there is also a relationship between episodes of mania, impaired inhibitory control, and issues with selective attention. Moreover, these cognitive impairments might be included in the initial phases of processing observed in N100 responses in depression, while processing impairment could be pervasive in mania that results in P300 delays.