Inhibitory Deficits of Insomnia Disorder: A Meta-Analysis on Event Related Potentials in Auditory Oddball Task

BACKGROUND

Despite numerous studies on auditory event-related potentials (ERPs) in insomnia disorder (ID), the results are inconsistent across different ERP components (e.g. N1, P2, P3, and N350), types of auditory stimuli (e.g. standard and deviant), and stages of sleep (e.g. wakefulness, NREM sleep, and REM sleep). In light of this variability, we conducted a systematic meta-analysis of previous auditory ERP studies in ID to provide a quantitative review of the existing literature.

METHODS

Relevant literatures were searched on the Embase, PubMed/MEDLINE, PsycINFO and Cochrane Library. A total of 12 studies comprising 497 participants were finally included in this meta-analysis. The study protocol was registered with PROSPERO under the registration number CRD42022308348.

RESULTS

We found that patients with ID have significantly decreased N1 (Hedges' g = 0.34, 95%CI [0.04, 0.65]) and P3 (Hedges'g = -1.21, 95%CI [-2.37, -0.06]) amplitudes during wakefulness. In addition, decreases in P2 (Hedges'g = -0.57, 95%CI [-0.96, -0.17]) amplitude during wakefulness and N350 (Hedges' g = 0.73, 95%CI [0.36, 1.09]) amplitude during NREM.

CONCLUSIONS

This meta-analysis represents the first systematic investigation of ERP features across different stages of sleep in individuals with ID. Our results suggest that in patients with insomnia, the absence or deficiency of arousal inhibition during the nighttime sleep initiation or maintenance process may interfere with the normal process of sleep.

Functional connectivity correlates of attentional networks in insomnia disorder: A pilot study

Insomnia disorder has been associated with poor executive functioning. Functional imaging studies of executive functioning in insomnia are scarce and inconclusive. Because the Attentional Network Test relies on well-defined cortical networks and sensitively distinguishes different aspects of executive function, it might reveal brain functional alterations in relatively small samples of patients. The current pilot study assessed functional connectivity during the Attentional Network Test performed using magnetic resonance imaging in 12 participants with insomnia and 13 self-defined good sleepers. ANCOVAs were used to evaluate group differences in performance and functional connectivity in the regions of interest representing the attentional networks (i.e. alerting, orienting and executive control) at p < 0.05, uncorrected. During the orienting part, participants with insomnia showed weaker connectivity of the precentral gyrus with the superior parietal lobe (false discovery rate-corrected), while they showed stronger connectivity between premotor and visual regions. Individual differences in connectivity between premotor and visual regions correlated inversely with reaction time. Reaction times suggested more efficient executive control in participants with insomnia compared with good sleepers. During the executive control part, participants with insomnia showed stronger connectivity of thalamic parts of the arousal circuit with the middle frontal and the occipital gyri. Conversely, connectivity between the inferior and superior frontal gyri was weaker. Participants with insomnia seem to recruit more cortical resources in visuo-motor regions to orient attention than good sleepers do, and seem to have enhanced executive control that relates to stronger connectivity of arousal-related thalamic areas. This latter result should be treated with caution and requires confirmation.

Altered brain activity related to inhibitory processing in youth with insomnia

Insomnia has been shown to negatively affect one's cognitive functioning. While there has been some evidence suggesting sleep disruption in relation to impaired inhibitory control, a major component of executive function, little is known about the underlying neural processing in insomnia. The current study aimed to examine the differences in the behavioral responses and electroencephalography (EEG) correlates of inhibitory control between youths with insomnia and healthy sleepers. Twenty-eight participants with insomnia disorder and 31 healthy sleeper controls aged between 15 and 25 completed the study. Electroencephalographic activity was recorded during the Cued Go/NoGo (CGNG) task, a task assessing inhibitory control. Although insomnia group exhibited comparable behavioral performance to the healthy sleeper group, they showed impaired attention preparation, as displayed by a smaller contingent negative variation (CNV) component (F = 4.10, p = 0.048) after cue onset; and demonstrated impaired inhibitory control, as evidenced by smaller N2 and theta power on 200-350 ms (MANCOVA multivariate Group effect, F = 5.85, p < 0.001). The results suggested that youths with insomnia demonstrated altered brain activity during inhibitory control, despite their comparable behavioral performance. Given that impaired inhibitory control is often implicated in psychopathology, future studies with a longitudinal design are needed to further explore the long-term impacts and trajectory of altered inhibitory control in youths with insomnia.

Behavioral and neural dynamics of cognitive control in the context of rumination

Rumination is a characteristic feature of several clinical disorders (e.g., major depressive disorder, insomnia disorder). Emerging evidence suggests that a reduced flexibility in the balance between proactive and reactive control might be related to trait rumination. This study aimed to investigate the proactive-reactive control balance in the context of trait rumination. In the current study, we investigated behavioral performance and event-related potentials (ERPs) while participants were performing an AX- Continuous Performance Task, to evaluate whether a shift towards more reactive control (i.e., conflict monitoring and resolution) at the expense of proactive control (i.e., maintenance and updating of task-relevant information) is associated with increased trait rumination. Our behavioral results as well as our ERP results did not demonstrate that a shift towards more reactive control at the expense of proactive control was associated with increased trait rumination. Future research is needed to investigate the proactive-reactive control balance in the context of trait rumination. This study is the first to explore the recruitment dynamics of cognitive control using behavioral as well as electrophysiological measures in the context of rumination.