The auditory P300 event-related potential (ERP) and performance on neuropsychological tests were evaluated in 26 subjects with schizophrenia, 19 with bipolar affective disorder, and 27 controls. The schizophrenic and the bipolar groups were similar in having prolonged P300 latency recorded from central and temporal leads. The P300 was significantly reduced in amplitude in the schizophrenic group at midline leads and the left temporal lead but was not significantly reduced in amplitude at any electrode site when the bipolar group was compared to controls. Schizophrenics performed significantly less well than bipolars and controls on tests of verbal fluency and, within this group, a significant correlation was found between the latency of P300 and verbal fluency test scores. While the bipolar group of patients was similar to the schizophrenic group in having prolonged P300 latency, these groups differed in P300 amplitude, performance on verbal fluency tests, and the relationship between the physiological and neuropsychological variables.
"Some studies of the event-related potential in bipolar disorder have identified reduced P300 amplitudes (Muir et al., 1991; Salisbury et al., 1998, 1999; El-Badri et al., 2001; O'Donnell et al., 2004a, 2004b; Fridberg et al., 2009), whereas other studies have reported no difference between healthy controls and patients with bipolar disorder (Souza et al., 1995; Strik et al., 1998; Hall et al., 2007; Kaya et al., 2007; Schulze et al., 2007, 2008). Furthermore, three studies reported prolonged P300 latency (O'Donnell et al., 2004; Turetsky et al., 2007; Schulze et al., 2008), whereas Salisbury et al. (1999) did not detect any delay in P300 latency in bipolar disorder. "
[Show abstract][Hide abstract] ABSTRACT: Decreased delta oscillation upon cognitive load is common in patients with Alzheimer‘s disease, mild cognitive impairment, and schizophrenia. However, there is no previous study analyzing the delta responses in euthymic medication-free patients with bipolar disorder. Participants comprised 22 euthymic medication-free patients with DSM-IV diagnoses of bipolar disorder and 21 healthy controls who were matched to the patients for sex, age, and education. Electroencephalographic activity was recorded at 30 electrode sites using an application of an auditory oddball paradigm. The maximum peak-to-peak amplitudes for each subject‘s averaged delta response (0.5–3.5 Hz) were measured. There was a significant intergroup difference in evoked and event-related delta (0.5–3.5 Hz) responses. Post hoc comparisons revealed that the event-related delta oscillatory responses of the bipolar patient group were significantly lower than those of the healthy control group over the temporoparietal and occipital electrode sites. Euthymic bipolar patients showed reduced event-related delta oscillatory responses in comparison to healthy subjects under cognitive load. The decrease of delta oscillations may be a common phenomenon that can be observed in different neuropsychiatric disorders with cognitive dysfunction.
"Reduced amplitude of the auditory P300, especially the P3b subcomponent, has been consistently reported in patients with schizophrenia (Turetsky et al., 2007; van der Stelt and Belger, 2007). Although reduced P300 amplitude is not specific to schizophrenia, the observed deficits are distinguishable in several aspects from the P300-deficits in Alzheimer disease (marked latency prolongation), alcoholism (more visual than auditory abnormalities) and depression (state-dependent abnormalities), suggesting different underlying neural mechanisms (Souza et al., 1995; Salisbury et al., 1999; Turetsky et al., 2007). However , since P300 amplitudes at centro-parietal sites in patients with bipolar disorder manifesting psychotic symptoms were not distinguishable from those of patients with schizophrenia, it was suggested that decreased P300 amplitude at these sites may mark functional psychosis in general (Bestelmeyer et al., 2009). "
"Although we did not aim to review spontaneous EEG and ERP research in BD, some important points should be noted before reviewing evoked/ event-related oscillations in BD patients. The literature includes several previous investigations of spontaneous EEG, ERP, and spontaneous MEG in bipolar patients (Cook et al., 1986; Dewan et al., 1988; Small et al., 1989, 1998; Gerez and Tello, 1992; Kano et al., 1992; Clementz et al., 1994; Koles et al., 1994; Souza et al., 1995; Schulz et al., 2000; El-Badri et al., 2001; Ikeda et al., 2002; Bas¸ar et al., 2012). These studies found generalized slowing, increased delta and theta power. "
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