The effect of cannabis on emotional processing was investigated using event-related potential paradigms (ERPs). ERPs associated with emotional processing of cannabis users, and non-using controls, were recorded and compared during an implicit and explicit emotional expression recognition and empathy task. Comparisons in P3 component mean amplitudes were made between cannabis users and controls. Results showed a significant decrease in the P3 amplitude in cannabis users compared to controls. Specifically, cannabis users showed reduced P3 amplitudes for implicit compared to explicit processing over centro-parietal sites which reversed, and was enhanced, at fronto-central sites. Cannabis users also showed a decreased P3 to happy faces, with an increase to angry faces, compared to controls. These effects appear to increase with those participants that self-reported the highest levels of cannabis consumption. Those cannabis users with the greatest consumption rates showed the largest P3 deficits for explicit processing and negative emotions. These data suggest that there is a complex relationship between cannabis consumption and emotion processing that appears to be modulated by attention.
The default mode network (DMN) is the most-prominent intrinsic connectivity network, serving as a key architecture of the brain’s functional organization. Conversely, dysregulated DMN is characteristic of major neuropsychiatric disorders. However, the field still lacks mechanistic insights into the regulation of the DMN and effective interventions for DMN dysregulation. The current study approached this problem by manipulating neural synchrony, particularly alpha (8 to 12 Hz) oscillations, a dominant intrinsic oscillatory activity that has been increasingly associated with the DMN in both function and physiology. Using high-definition alpha-frequency transcranial alternating current stimulation (α-tACS) to stimulate the cortical source of alpha oscillations, in combination with simultaneous electroencephalography and functional MRI (EEG-fMRI), we demonstrated that α-tACS (versus Sham control) not only augmented EEG alpha oscillations but also strengthened fMRI and (source-level) alpha connectivity within the core of the DMN. Importantly, increase in alpha oscillations mediated the DMN connectivity enhancement. These findings thus identify a mechanistic link between alpha oscillations and DMN functioning. That transcranial alpha modulation can up-regulate the DMN further highlights an effective noninvasive intervention to normalize DMN functioning in various disorders.
Visual-cortex-DMN alpha dysrhythmia in PTSD p. 3 3 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 interregional 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 Visual-cortex-DMN alpha dysrhythmia in PTSD p. 4 4 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 restingstate 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 temporalspatial network pathology, promoting network-based neural oscillatory interventions.
Anticipation is a universal preparatory response essential to the survival of an organism. Although meta-analytic synthesis of the literature exists for the anticipation of reward, a neuroimaging-based meta-analysis of the neural mechanisms of aversive anticipation is lacking. To address this gap in the literature, we ran an activation likelihood estimate (ALE) meta-analysis of 63 fMRI studies of aversive anticipation across multiple sensory modalities. Results of the ALE meta-analysis provide evidence for a core circuit involved in aversive anticipation, including the anterior insula, anterior cingulate cortex, mid-cingulate cortex, amygdala, thalamus, and caudate nucleus among other regions. Direct comparison of aversive anticipation studies using tactile versus visual stimuli identified additional regions involved in sensory specific aversive anticipation across these sensory modalities. Results from complementary multi-study voxel-wise and NeuroSynth analyses generally provide converging evidence for a core circuit involved in aversive anticipation. The multi-study voxel-wise analyses also implicate a more widespread preparatory response across sensory, motor, and cognitive control regions during more prolonged periods of aversive anticipation. The potential roles of these structures in anticipatory processing as well as avenues for future research are discussed.
As part of an ongoing research program into the relationship between cannabis use and emotion processing, participants were assessed on their level of cannabis exposure using the Recreational Cannabis Use Examination, a measure developed specifically to assess cannabis use in Colorado post state legalization. Three groups were created based on self-reported use: a control group who have never used, a casual user group and a chronic user group. Each participant also completed two measures of mood assessment, the Center for Epidemiologic Studies Depression Scale and the State-Trait Anxiety Inventory. Relationships between cannabis use groups and scores on these measures were then analyzed using both correlations and multivariate analysis of variance. Results indicate a relationship between casual cannabis use and scoring highly for depressive symptomatology on the Center for Epidemiologic Studies Depression Scale. There were no significant relationships between cannabis use and scores on the State-Trait Anxiety Inventory.
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