Regional Brain Correlates of Beta Bursts in Health and Psychosis: A Concurrent Electroencephalography and Functional Magnetic Resonance Imaging Study

Abstract

Background There is emerging evidence for abnormal beta oscillations in psychosis. Beta oscillations are likely to play a key role in the coordination of sensorimotor information that is crucial to healthy mental function. Growing evidence suggests that beta oscillations typically manifest as transient beta bursts that increase in probability following a motor response, observable as post-movement beta rebound. Evidence indicates that post-movement beta rebound is attenuated in psychosis, with greater attenuation associated with greater symptom severity and impairment. Delineating the functional role of beta bursts therefore may be key to understanding the mechanisms underlying persistent psychotic illness. Methods We used concurrent electroencephalography and functional magnetic resonance imaging to identify blood oxygen level–dependent correlates of beta bursts during the n-back working memory task and intervening rest periods in healthy control participants ( n = 30) and patients with psychosis ( n = 48). Results During both task blocks and intervening rest periods, beta bursts phasically activated regions implicated in task-relevant content while suppressing currently tonically active regions. Patients showed attenuated post-movement beta rebound that was associated with persisting disorganization symptoms as well as impairments in cognition and role function. Patients also showed greater task-related reductions in overall beta burst rate and showed greater, more extensive, beta burst–related blood oxygen level–dependent activation. Conclusions Our evidence supports a model in which beta bursts reactivate latently maintained sensorimotor information and are dysregulated and inefficient in psychosis. We propose that abnormalities in the mechanisms by which beta bursts coordinate reactivation of contextually appropriate content can manifest as disorganization, working memory deficits, and inaccurate forward models and may underlie a core deficit associated with persisting symptoms and impairment.

Spontaneous activity competes with externally evoked responses in sensory cortex

“…As long as this baseline activity is low, an incoming stimulus would deactivate the spontaneously active network and shift the focus from the internal state to the external environment (1). A recent study (49) demonstrated that sensory-motor beta-bursts correlated with an increase in the task-suppressed hemodynamic signal in the sensory-motor network. A near-threshold stimulus was given upon detection of exactly 0 (quiet), 150 (low), 300 (medium), or more than 400 (high) burst samples during the detection window and the 600 ms preceding it.…”

Imprecise Predictive Coding Is at the Core of Classical Schizophrenia

“…Although PMBR is usually quantified by averaging the beta power across a time window following movement, observation of data acquired in single trials reveals that the smooth peak of beta activity observed in trial averaged data actually represents the superposition of transient bursts of beta activity with duration of order 150 ms occurring with increased probability in the PMBR time window. In a study employing concurrent EEG and fMRI to assess brain activity during the n-back working memory task, Briley et al (2021) confirmed that beta-burst rate following button press responses was diminished in schizophrenia, and also in psychotic bipolar disorder, compared with healthy controls. The reduction was less marked in the bipolar cases.…”

“…So far there is limited evidence that assessment of the relevant symptoms and cognitive measures are sufficiently sensitive and reliable to provide clinically useful estimates of prognosis in an individual case. However, the evidence that classical features are correlated with electrophysiological features such as inter-trial coherence during target detection tasks ( Doege et al, 2010 ) and beta-bursts related to movement ( Rathnaiah et al, 2020 ; Briley et al, 2021 ; Gascoyne et al, 2021 ) indicates a practical approach to enhancing prediction. It is practical to measure these electrophysiological features in routine clinical practice.…”

“…Furthermore, the analysis by Briley et al (2021) of the BOLD signal assessed using fMRI revealed that beta-bursts are associated with the reactivation of a pattern of brain activity representing task-relevant content of working memory. In the context of the n-back task, in which the target stimuli were letters of the alphabet, the spatial distribution of BOLD signal associated with the occurrence of beta-bursts included areas implicated in the articulation of speech, processing of speech sounds and also sensorimotor areas engaged in the required motor response.…”

Unveiling the Associations between EEG Indices and Cognitive Deficits in Schizophrenia-Spectrum Disorders: A Systematic Review

“…Two studies that used resting-state conditions in SCZ found that beta power was positively correlated (decreased in EEG activity—worse cognitive performance) with different cognitive functions, such as emotion recognition [ 85 ], vigilance, working memory, visual and verbal memory [ 109 ]. Furthermore, two studies investigating task-related activity reported a positive association of evoked beta bursts [ 114 ] and evoked beta activity [ 99 ] with working memory. However, also a lack of associations between beta power and verbal learning [ 86 ], working memory [ 86 ] and metacognitive functions [ 122 ] has been reported.…”