Amplitude reduction of the oddball P3 wave is a well-replicated but non-specific finding of schizophrenia. The time-frequency analysis of single-trial ERP data allows to specify in a reliable manner whether the P3 reduction in schizophrenia is due to the decreased P3 response in single trials or due to the inter-trial variability in the timing of the response. Since the delta response most strongly contributes to the P3 amplitude, we focused to the low frequency range of the time-frequency transformed data. EEG was recorded from chronic schizophrenia patients and matched healthy controls during a simple visual oddball task. The wavelet transforms of the averaged ERP and the single trials were computed to investigate the amplitudes of the evoked (phase-locked) and total (phase-locked+non-phase-locked) delta (1-3 Hz) responses, respectively. Evoked delta activity and P3 amplitude to target stimuli were both reduced significantly in patients with schizophrenia, whereas no such difference was obtained for the total delta activity. The significant reduction of the evoked delta response and the absence of such a difference in the total delta response of schizophrenia patients reveals that the delta band response is weakly phase-locked to stimulus in schizophrenia. This result suggests that the reduced P3 amplitudes in the averaged ERPs of schizophrenia patients result from a temporal jitter in the activation of neural circuits engaged in P3 generation.
"One of the common parameters seen in ERO studies in different pathologies is the decrease in delta activity upon cognitive load (Başar and Güntekin, 2013). Previous studies related to brain pathological states indicate that the amplitude of event-related delta oscillations decreases in Alzheimer's disease (Yener et al., 2008), mild cognitive impairment (Kurt et al., 2014; Yener et al., 2013), schizophrenia (Ergen et al., 2008; Ford et al., 2008), bipolar disorder (Atagün et al., 2014) and alcoholism (Kamarajan et al., 2004). However, there are few studies in the literature investigating delta ERO in healthy elderly (Schmiedt-Fehr and Başar-Eroglu, 2011; Schmiedt-Fehr et al., 2011). "
"Significant differences between patients and controls on measures of attention, memory and problem solving disappear when results on the DSST are added as a covariate (Rodriguez-Sanchez et al., 2007) and a processing speed index fully mediated the effects of verbal memory on functional outcomes (Ojeda et al., 2008). Patients with schizophrenia have repeatedly been shown to have reduced amplitude of late ERP components (Pfefferbaum et al., 1989; Turetsky et al., 2007; Ergen et al., 2008; Kuperberg et al., 2011; Strauss et al., 2013). In healthy subjects, the amplitude of these components can be affected by the duration and intensity of the stimulus. "
[Show abstract][Hide abstract] ABSTRACT: This study determined whether increasing stimulus duration for patients with schizophrenia normalized late Event Related Potentials (ERPs) associated with modulation of response to emotion-evoking stimuli. These ERPs are decreased in patients versus healthy controls when both view stimuli of the same duration. Subjects viewed pictures of hands and judged whether the events depicted were painful or non-painful. Pictures were presented to patients for 500 or 800ms and to healthy controls for 200 or 500ms. Participants were 19 adult outpatients meeting DSM-IV criteria for schizophrenia or schizoaffective disorder and 18 healthy controls, as assessed by the Structured Clinical Interview. ERPs to neutral stimuli during a 350-900ms window following stimulus onset were subtracted from ERPs during this same response window to pain stimuli. The area under this difference wave reflected the degree of pain-related positivity and was the dependent measure for analysis. Patient late-positive ERP responses following 500 and 800ms stimuli were highly similar to responses in healthy controls following 200 and 500ms stimuli respectively. Patients and controls differed significantly when responses to 500ms stimuli were compared. People with schizophrenia are known to process information more slowly than healthy people. Our results indicate that slowed early processing of sensory input may limit engagement of higher cognitive and regulatory processes in patients with schizophrenia. This may be one reason that self-regulation is compromised in patients, and may help explain why measures of slowed information processing account for so much variance in other cognitive deficits in schizophrenia.
Schizophrenia Research 08/2014; 158(1-3). DOI:10.1016/j.schres.2014.07.012 · 3.92 Impact Factor
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