Enhanced resting-state oscillations in schizophrenia are associated with decreased synchronization during inattentional blindness

Abstract

Patients suffering from schizophrenia have been characterized by an apparent lack of theta (around 6 Hz) and gamma (>40 Hz) brain oscillatory activity during task execution. The neurocognitive reasons for these abnormal synchronization patterns, however, remain elusive. Recording the electroencephalogramm (EEG) during a selective visual attention task, the current study investigates whether abnormal brain oscillatory resting-state activity in the theta band might account for a lack of task-related brain oscillatory activity in schizophrenia. EEGs were recorded from 26 patients with schizophrenia and 26 healthy matched controls during rest and during the execution of a selective visual attention task, in which an unexpected object (monkey) appeared on the screen. On a behavioral level, patients were less likely to report perceiving the unexpected event than controls. Controls showed a stronger increase in task-related theta power than patients in prefrontal, parietal, and occipital brain regions. Task-related theta power change differed between patients who perceived, and patients who did not perceive the unexpected event. Moreover, patients showed higher levels of theta power during rest than controls, whereas the absolute theta power values during the selective attention task did not differ between groups. These results suggest that the failure to increase oscillatory activity during a cognitive task can be accounted for by abnormally high oscillatory activity in a resting state. This finding has important implications for future studies examining abnormal brain oscillatory activity in schizophrenia, which usually treat resting-state activity as a baseline for task-related activity.

Predictive Suppression of Cortical Excitability and Its Deficit in Schizophrenia

“…2C). The mainly theta frequency (ϳ7 Hz) ongoing activity observable in the passive condition was significantly larger in patients (see also Hanslmayr et al, 2012) and showed a frontocentral maximum in topographic maps consistent with at least partly auditory generators (Fig. 5A-C).…”

“…Even though, as our results suggest, the suppression of neuronal excitability predominates in auditory cortical regions at critical time points, this only serves to attenuate ignored frequency content and enhance the sensory representation of attended stimuli. As opposed to this, the goal of automatic or passive predictive processes is to suppress selfgenerated or frequently occurring nonrelevant items, and only signal whether a change is detected (Houde et al, 2002;Friston, 2005;Baldeweg, 2006;Bäss et al, 2008;Winkler et al, 2009;Chen et al, 2011;Costa-Faidella et al, 2011;Knolle et al, 2013). In these cases, an inverse pattern would be ideally suited as the mechanism: oscillations entrained with their suppressive phases could be centered on the spectrotemporal properties of selfgenerated or frequently occurring nonrelevant sounds, while the rest of auditory cortex could be entrained with their opposing, high-excitability phases.…”

“…There is also rapidly accumulating evidence for the involvement of thalamocortical networks and the TRN dysfunction in the pathogenesis of schizophrenia (Martínez et al, 2008(Martínez et al, , 2012Ferrarelli and Tononi, 2011;Pinault, 2011;Vukadinovic and Rosenzweig, 2012). Furthermore, treatment with a NMDA antagonist, such as the psychotomimetic drug phencyclidine reduces delta activity and increases ongoing gamma activity within thalamocortical loops (Hong et al, 2010;Kiss et al, 2011). Thus, the observed deficits in delta entrainment and gamma modulation may reflect underlying NMDA receptor dysfunction in the thalamocortical circuitry, consistent with glutamatergic theories of schizophrenia (Javitt and Zukin, 1991).…”

EEG Power Asymmetry and Functional Connectivity as a Marker of Treatment Effectiveness in DBS Surgery for Depression

“…This synchronization is observed in oscillatory activity recorded by EEG and MEG and refers to a consistent relation between the phases of the oscillatory activity of two brain regions that can be assessed from the measured time series . Recent studies on a host of neurological disorders including Alzheimer's disease (de Haan et al, 2012;Tahaei et al, 2012), Parkinson disease (Babiloni et al, 2011;Bosboom et al, 2009;Stoffers et al, 2008), schizophrenia (Hanslmayr et al, 2012;Hinkley et al, 2011;Jalili et al, 2007) and epileptic seizures (Mormann et al, 2003;Stam et al, 2007a) have demonstrated a disruption in this synchronization in various frequency bands. In MDD, impairments in synchronization in both y and a bands have been reported (Fingelkurts et al, 2007;LinkenkaerHansen et al, 2005).…”

Resting State Activity and the "Stream of Consciousness" in Schizophrenia--Neurophenomenal Hypotheses

“…Recent resting state electroencephalogram (EEG) showed increased coherence in basically all low-and high-frequency bands including delta, theta, alpha, and gamma bands within and between hemispheres in schizophrenia. [29][30][31][32][33] Most interestingly, the study by Spencer 33 could relate the increased gamma power in auditory cortex to reduced stimulusevoked activity in response to auditory stimuli with the former predicting (ie, correlating) the latter. This suggests clear relationship between increased resting state gamma power and reduced task-evoked activity in gamma (see in what follows).…”