The dependence of P300 amplitude on gamma synchrony breaks down in schizophrenia

Abstract

Introduction-Auditory P300 amplitude reduction in schizophrenia is canonical and may be explained by poor synchronization or reduced power of the underlying neural activity. We asked if patients have reduced synchrony and power, and whether together with P300 amplitude, they make unique or overlapping contributions to the discrimination between patients and controls. We also asked whether people who have large P300s have higher power and greater synchrony of neural activity, and if the relationships between P300 and power and synchrony are different in patients and healthy controls.Methods-We recorded EEG data from 22 controls and 21 patients with schizophrenia (DSM-IV) while they performed an auditory target (p=.10) detection task. We used wavelet analyses to estimate total power and synchrony of delta, theta, alpha, beta, and gamma activity in a 50ms window around the peak of the P300 to the target from the single trial data. We measured P300 amplitude from the average of the single trials, in a 50ms window around its peak.Results and Conclusions-P300 amplitude and delta and theta synchrony were reduced in patients; delta power and synchrony better distinguished between groups than P300 amplitude. In healthy controls, but not patients, gamma synchrony predicted P300 amplitude, but delta did not. In patients, P300 and gamma synchrony are affected by independent factors; the relationship between them is attenuated by an additional pathophysiological process.

Ketamine Modulates Theta and Gamma Oscillations

“…Of special note, ketamine attenuates the depression in late induced theta power, leaving only a short depressed activity after the second click located in the high theta frequency range. This may correlate with recent human EEG data showing a decrease in the 8-12 Hz total power during a P300 task in the control healthy group and an attenuation of this decrease in patients with schizophrenia (Ford, Roach, Hoffman, & Mathalon, 2008). Because ketamine is thought to exert its effects via blocking NMDA receptors, these data support their role in mediating the balance between theta and gamma responses to sensory stimuli with implications for dysfunction in schizophrenia.…”

Exploring the dynamics of P300 amplitude in patients with schizophrenia

“…These mostly concern the consistency of findings regarding the gamma band and the lack of contribution of slow frequencies for P300 reported by Ford et al (2008). Given the high dependency of the P300 on the synchrony and power of delta band activity, and the consistent reports of reduced slow frequency activity in patients with schizophrenia, a relation between P300 and delta activity would be expected for both control and patient samples.…”

“…Others (e.g., see Ergen et al, 2008) also reported a reduced visual P300 and evoked delta power, but not total delta power, which suggests that temporal jitter on the onset of the neural generators of the P300 component may result in less stimulus-locked delta activity. Ford et al (2008) have shown that the reduced P300 may be accounted by a reduction in power and ITC on the theta and gamma bands. They have reported that the amplitude of the P300 displays a dependence on the synchrony of the gamma band activity in controls, and that this dependency is absent in patients.…”

Decrease of delta oscillatory responses is associated with increased age in healthy elderly

“…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 .…”