Transcutaneous Auricular Vagus Nerve Stimulation Modulates the Prefrontal Cortex in Chronic Insomnia Patients: fMRI Study in the First Session

Abnormal dynamic functional connectivity and topological properties of cerebellar network in male obstructive sleep apnea

PURPOSE

To investigate dynamic functional connectivity (dFC) within the cerebellar-whole brain network and dynamic topological properties of the cerebellar network in obstructive sleep apnea (OSA) patients.

METHODS

Sixty male patients and 60 male healthy controls were included. The sliding window method examined the fluctuations in cerebellum-whole brain dFC and connection strength in OSA. Furthermore, graph theory metrics evaluated the dynamic topological properties of the cerebellar network. Additionally, hidden Markov modeling validated the robustness of the dFC. The correlations between the abovementioned measures and clinical assessments were assessed.

RESULTS

Two dynamic network states were characterized. State 2 exhibited a heightened frequency, longer fractional occupancy, and greater mean dwell time in OSA. The cerebellar networks and cerebrocerebellar dFC alterations were mainly located in the default mode network, frontoparietal network, somatomotor network, right cerebellar CrusI/II, and other networks. Global properties indicated aberrant cerebellar topology in OSA. Dynamic properties were correlated with clinical indicators primarily on emotion, cognition, and sleep.

CONCLUSION

Abnormal dFC in male OSA may indicate an imbalance between the integration and segregation of brain networks, concurrent with global topological alterations. Abnormal default mode network interactions with high-order and low-level cognitive networks, disrupting their coordination, may impair the regulation of cognitive, emotional, and sleep functions in OSA.

Advances in acupuncture regulation on the autonomic nervous system from 2013 to 2022: A bibliometric analysis via citespace

OBJECTIVE

To understand research advances and frontiers of acupuncture regulation on the autonomic nervous system (ANS) over the past decade through a bibliometric analysis.

METHODS

Publications related to acupuncture regulation on the ANS were retrieved from the Web of Science Core Collection (WoSCC) database. CiteSpace software was used to analyze the datasets and generate knowledge maps.

RESULTS

A total of 445 relevant publications published between 2013 and 2022 were included in this bibliometric analysis. The number of annual publications fluctuated from 2013 to 2016 but increased gradually from 2016 to 2022. China produced the highest number of publications, while the USA established the most extensive cooperation relationships. China Academy of Chinese Medical Science was the most productive institution. Chen Jiande D.Z. was the most prolific author and Rong Peijing holds the most extensive cooperation network. Han Jisheng was the most co-cited author. Relevant research involved mechanism exploration and clinical efficacy research, and "anti-inflammatory effect" was the most active research topic, especially cholinergic anti-inflammatory mechanisms. The most cited references mainly focused on inflammation. Gastrointestinal and cardiovascular disorders were the most active medical conditions studied in this field.

CONCLUSIONS

Research related to acupuncture regulation on the ANS mainly focused on anti-inflammation, and regulating gastrointestinal and cardiovascular function over the past decade. However, the mechanisms of the autonomic effects of acupuncture need further investigation. High-quality clinical studies are required to determine the optimal parameters of acupuncture for clinical application.

Clinical application of transcutaneous auricular vagus nerve stimulation: a scoping review

PURPOSE

Transcutaneous auricular vagus nerve stimulation (taVNS) is an emerging non-invasive neuromodulation therapy. This study aimed to explore the therapeutic use of taVNS, optimal stimulation parameters, effective sham protocols, and safety.

METHODS

A scoping review was conducted. Five databases and grey literature were searched. The data extracted included stimulation parameters, adverse events (AEs), and therapeutic effects on clinical outcomes.

RESULTS

109 studies were included. taVNS was used across 21 different clinical populations, most commonly in psychiatric, cardiac, and neurological disorders. Overall, 2,214 adults received active taVNS and 1,017 received sham taVNS. Reporting of stimulation parameters was limited and inconsistent. taVNS appeared to have a favourable therapeutic effect across a wide range of clinical populations with varied parameters. Three sham protocols were reported but their effectiveness was documented in only two of the 54 sham-controlled studies. Most reported adverse events were localised to stimulation site.

CONCLUSION

There is growing evidence for taVNS therapeutic effect. taVNS appears safe and tolerable. Sham protocols need evaluation. Standardised and comprehensive reporting of both stimulation parameters and adverse events is required. Two different questionnaires have been proposed to evaluate adverse events and the effectiveness of sham methods in blinding participants.

Towards the neurobiology of insomnia: A systematic review of neuroimaging studies

Insomnia disorder signifies a major public health concern. The development of neuroimaging techniques has permitted to investigate brain mechanisms at a structural and functional level. The present systematic review aims at shedding light on functional, structural, and metabolic substrates of insomnia disorder by integrating the available published neuroimaging data. The databases PubMed, PsycARTICLES, PsycINFO, CINAHL and Web of Science were searched for case-control studies comparing neuroimaging data from insomnia patients and healthy controls. 85 articles were judged as eligible. For every observed finding of each study, the effect size was calculated from standardised mean differences, statistic parameters and figures, showing a marked heterogeneity that precluded a comprehensive quantitative analysis. From a qualitative point of view, considering the findings of significant group differences in the reported regions across the articles, this review highlights the major involvement of the anterior cingulate cortex, thalamus, insula, precuneus and middle frontal gyrus, thus supporting some central themes in the debate on the neurobiology of and offering interesting insights into the psychophysiology of sleep in this disorder.

Abnormal alterations of regional spontaneous neuronal activity and functional connectivity in insomnia patients with difficulty falling asleep: a resting-state fMRI study

BACKGROUND

Insomnia disorder (ID) seriously affects people's daily life. Difficulty falling asleep is the most commonly reported complaint in patients with ID. However, the mechanism of prolonged sleep latency (SL) is still obscure. The aim of our present study was to investigate the relationship between prolonged SL and alterations in spontaneous neural activity and brain functional connectivity (FC) in ID patients using functional magnetic resonance imaging (fMRI).

METHODS

A total of 52 insomniacs with difficulty falling asleep and 30 matched healthy controls (HCs) underwent resting-state fMRI. The amplitude of low-frequency fluctuation (ALFF) was measured and group differences were compared. The peak areas with significantly different ALFF values were identified as the seed regions to calculate FC to the whole brain. SL was assessed by a wrist actigraphy device in ID patients. The Pittsburgh Sleep Quality Index (PSQI), Hamilton Anxiety Rating Scale (HAMA), and Hyperarousal Scale (HAS) were evaluated in both ID patients and HCs. Finally, correlation analyses were performed between the clinical features and FC/ALFF values.

RESULTS

ID patients showed higher PSQI, HAMA, HAS scores than HCs. The functional MRI results indicated increased ALFF value in the left insula and right amygdala and decreased ALFF value in the right superior parietal lobe (SPL) in ID patients. The seed-based FC analysis demonstrated increased FC between the left insula and the bilateral precentral gyrus and FC between the right amygdala and the left posterior cingulate cortex (PCC) in patients with ID. Correlation analysis indicated that the increased FC value of the right amygdala-left PCC was positively correlated with SL measured by actigraphy.

CONCLUSION

This study revealed abnormal regional spontaneous fluctuations in the right amygdala, left insula, and right SPL, as well as increased FC in the left insula-precentral and right amygdala-left PCC. Moreover, the prolonged SL was positively correlated with the abnormal FC in the right amygdala-left PCC in ID patients. The current study showed the correlation between prolonged SL and the abnormal function of emotion-related brain regions in ID patients, which may contribute to a better understanding of the neural mechanisms underlying difficulty falling asleep in patients with ID.

CLINICAL TRIAL REGISTRATION

http://www.chictr.org.cn ., ChiCTR1800015282. Registered on 20th March 2018.

Brain stimulation techniques as novel treatment options for insomnia: A systematic review

Despite the success of cognitive behavioural therapy for insomnia and recent advances in pharmacotherapy, many patients with insomnia do not sufficiently respond to available treatments. This systematic review aims to present the state of science regarding the use of brain stimulation approaches in treating insomnia. To this end, we searched MEDLINE, Embase and PsycINFO from inception to 24 March 2023. We evaluated studies that compared conditions of active stimulation with a control condition or group. Outcome measures included standardized insomnia questionnaires and/or polysomnography in adults with a clinical diagnosis of insomnia. Our search identified 17 controlled trials that met inclusion criteria, and assessed a total of 967 participants using repetitive transcranial magnetic stimulation, transcranial electric stimulation, transcutaneous auricular vagus nerve stimulation or forehead cooling. No trials using other techniques such as deep brain stimulation, vestibular stimulation or auditory stimulation met the inclusion criteria. While several studies report improvements of subjective and objective sleep parameters for different repetitive transcranial magnetic stimulation and transcranial electric stimulation protocols, important methodological limitations and risk of bias limit their interpretability. A forehead cooling study found no significant group differences in the primary endpoints, but better sleep initiation in the active condition. Two transcutaneous auricular vagus nerve stimulation trials found no superiority of active stimulation for most outcome measures. Although modulating sleep through brain stimulation appears feasible, gaps in the prevailing models of sleep physiology and insomnia pathophysiology remain to be filled. Optimized stimulation protocols and proof of superiority over reliable sham conditions are indispensable before brain stimulation becomes a viable treatment option for insomnia.

The effect of TENS on sleep: A pilot study

BACKGROUND

Insomnia is the second most common neuropsychiatric disorder, but the current treatments are not very effective. There is therefore an urgent need to develop better treatments. Transcutaneous electrical nerve stimulation (TENS) may be a promising means of treating insomnia.

OBJECTIVE

This work aims to explore whether and how TENS modulate sleep and the effect of stimulation waveforms on sleep.

METHODS

Forty-five healthy subjects participated in this study. Electroencephalography (EEG) data were recorded before and after four mode low-frequency (1 Hz) TENS with different waveforms, which were formed by superimposing sine waves of different high frequencies (60-210 Hz) and low frequencies (1-6 Hz). The four waveform modes are formed by combining sine waves of varying frequencies. Mode 1 (M1) consists of a combination of high frequencies (60-110 Hz) and low frequencies (1-6 Hz). Mode 2 (M2) is made up of high frequencies (60-210 Hz) and low frequencies (1-6 Hz). Mode 3 (M3) consists of high frequencies (110-160 Hz) and low frequencies (1-6 Hz), while mode 4 (M4) is composed of high frequencies (160-210 Hz) and low frequencies (1-6 Hz). For M1, M3 and M4, the high frequency portions of the stimulus waveforms account for 50%, while for M2, the high frequency portion of the waveform accounts for 65%. For each mode, the current intensities ranged from 4 mA to 7 mA, with values for each participant adjusted according to individual tolerance. During stimulation, the subjects were stimulated at the greater occipital nerve by the four mode TENS.

RESULTS

M1, M3, and M4 slowed down the frequency of neural activity, broadened the distribution of theta waves, and caused a decrease in activity in wakefulness-related regions and an increase in activity in sleep-related regions. However, M2 has the opposite modulation effect.

CONCLUSION

These results indicated that low-frequency TENS (1 Hz) may facilitate sleep in a waveform-specific manner. Our findings provide new insights into the mechanisms of sleep modulation by TENS and the design of effective insomnia treatments.

Transcutaneous auricular vagus nerve stimulation in disorders of consciousness: A mini-narrative review

In this mini review, 6 studies that investigated the effects of transcutaneous auricular vagus nerve stimulation (taVNS) in patients with disorders of consciousness (DOC) were reviewed. Generally, the application of taVNS in patients with DOC appears to be effective (positive results in 5 of 6 studies) and safe. Furthermore, 4 studies that evaluated changes in the brain following taVNS reported positive results (2 studies, functional magnetic resonance imaging and 2 studies, electroencephalography). Based on our review of the 6 studies, we believe that research and clinical application of taVNS in DOC are in the initial stages and have the following limitations. First, there is a shortage of studies on this topic, with only 6 studies, 2 of which were case reports. Second, 5 studies were performed without control or sham groups. Third, there was no standardization of treatment schedules and electrical stimulation parameters. Therefore, further studies to overcome the above limitations should be encouraged; further original studies involving a larger number of patients in the control or sham groups are needed. However, studies on the optimal conditions (treatment schedule and electrical stimulation parameters) for taVNS in patients with DOC are necessary. Furthermore, neuroimaging studies should be undertaken to elucidate the neurological mechanisms for the recovery of impaired consciousness in DOC and the lasting effects of taVNS on the brain.

A coordinate-based meta-analysis of acupuncture for chronic pain: Evidence from fMRI studies

Background

Chronic pain (CP) patients tend to represent aberrant functional brain activity. Acupuncture is an effective clinical treatment for CP, and some fMRI studies were conducted to discover the alternation of brain regions after acupuncture therapy for CP. However, the heterogeneity of neuroimaging studies has prevented researchers from systematically generalizing the central mechanisms of acupuncture in the treatment of CP.

Methods

We searched bibliographic databases, including PubMed, EMBASE, PsycINFO, Web of Science Core Collection, ScienceDirect, China Academic Journal Network Publishing Database, etc., and trials registration platforms (From inception to September 1^st, 2022). Two independent researchers assessed the study's bias and quality. Furthermore, activation likelihood estimation (ALE) analysis was applied to explore aberrant brain functional activity and acupuncture's central mechanism for CP.

Results

Totally 14 studies with 524 CP patients were included in the study. ALE analysis showed that CP patients presented with decreased ALFF/ReHo in the precuneus, posterior cingulate cortex, right inferior parietal lobule, right superior temporal gyrus, cingulate gyrus, superior frontal gyrus, left medial frontal gyrus including medial prefrontal gurus, left middle frontal gyrus.

Conclusion

This ALE meta-analysis pointed out that acupuncture could modulate the default mode network, the frontoparietal network to treat CP. This provided a systematic summary of the neuroimage biomarker of acupuncture for the treatment of CP.

Systematic review registration

PROSPERO, identifier: CRD42021239633.

Therapeutic applications of transcutaneous auricular vagus nerve stimulation with potential for application in neurodevelopmental or other pediatric disorders

Non-invasive transcutaneous auricular vagus nerve stimulation (taVNS) as a newly developed technique involves stimulating the cutaneous receptive field formed by the auricular branch of the vagus nerve in the outer ear, with resulting activation of vagal connections to central and peripheral nervous systems. Increasing evidence indicates that maladaptive neural plasticity may underlie the pathology of several pediatric neurodevelopmental and psychiatric disorders, such as autism spectrum disorder, attention deficit hyperactivity disorder, disruptive behavioral disorder and stress-related disorder. Vagal stimulation may therefore provide a useful intervention for treating maladaptive neural plasticity. In the current review we summarize the current literature primarily on therapeutic use in adults and discuss the prospects of applying taVNS as a therapeutic intervention in specific pediatric neurodevelopmental and other psychiatric disorders. Furthermore, we also briefly discuss factors that would help optimize taVNS protocols in future clinical applications. We conclude from these initial findings that taVNS may be a promising alternative treatment for pediatric disorders which do not respond to other interventions.