Posttraumatic stress disorder is associated with alpha dysrhythmia across the visual cortex and the default mode network

Abstract

Anomalies in default mode network (DMN) activity and alpha (8-12 Hz) oscillations have been independently observed in posttraumatic stress disorder (PTSD). Recent spatiotemporal analyses suggest that alpha oscillations support DMN functioning via inter-regional synchronization and sensory cortical inhibition. Therefore, we examined a unifying pathology of alpha deficits in the visual-cortex-DMN system in PTSD. Human patients with PTSD (N = 25) and two control groups—patients with Generalized Anxiety Disorder (GAD; N = 24) and healthy controls (HC; N = 20)—underwent a standard eyes-open resting state (S-RS) and a modified resting state (M-RS) of passively viewing salient images (known to deactivate the DMN). High-density electroencephalogram (hdEEG) were recorded, from which intracortical alpha activity (power and connectivity/Granger causality) was extracted using the exact low-resolution electromagnetic tomography (eLORETA). Patients with PTSD (vs. GAD/HC) demonstrated attenuated alpha power in the visual cortex and key hubs of the DMN (posterior cingulate cortex/PCC and medial prefrontal cortex/mPFC) at both states, the severity of which further correlated with hypervigilance symptoms. With increased visual input (at M-RS vs. S-RS), patients with PTSD further demonstrated reduced alpha-frequency directed connectivity within the DMN (PCC→mPFC) and, importantly, from the visual cortex (VC) to both DMN hubs (VC→PCC and VC→mPFC), linking alpha deficits in the two systems. These interrelated alpha deficits align with DMN hypoactivity/hypoconnectivity, sensory disinhibition, and hypervigilance in PTSD, representing a unifying neural underpinning of these anomalies. The identification of visual-cortex-DMN alpha dysrhythmia in PTSD further presents a novel therapeutic target, promoting network-based intervention of neural oscillations.

SIGNIFICANCE STATEMENT Alpha (8-12 Hz) oscillations and the default mode network (DMN) both dominate the resting-state brain activity and are found to be closely related. In addition, aberrant alpha and DMN activities are both implicated in the pathophysiology of posttraumatic stress disorder (PTSD). Linking alpha and DMN aberrations in PTSD, our high-density EEG source analysis reveals that PTSD is associated with alpha power deficits across the DMN and visual cortex (VC) and deficient alpha-frequency connectivity from the VC to the DMN. That this visual-cortex-DMN alpha dysrhythmia further underpins hypervigilance symptoms in PTSD highlights a temporal-spatial network pathology, promoting network-based neural oscillatory interventions.