ABSTRACT
Background: The modulatory effect of transcutaneous auricular vagus nerve stimulation (taVNS) on attention has varied in previous studies. This inconsistency might be attributed to the combined influence of the modulation effect on the different attentional functions, including alerting, orienting and executive control. Aims: We aimed to preliminarily examine the modulatory effects of taVNS on different attentional functions. Methods: Fifty-nine healthy participants were recruited and were randomly assigned to taVNS (receiving taVNS for 20 minutes) or control (receiving taVNS for 30 seconds) groups. All participants underwent a dot-probe task before and after the taVNS/control intervention. Their behavioural performance and electroencephalographic signals during pre- and post-tests were recorded, and different observed variables were extracted and analysed to characterise different attentional systems. Results: We observed that active taVNS applied at the left ear significantly improved the overall behavioural performance, that is, shorter reaction time (RT) and lower intra-individual reaction time variability (IIRTV) for right-hand responses when compared with the control condition. In addition, active taVNS resulted in larger P3 and movement-related cortical potential (MRCP) amplitudes associated with right-hand reactions than the control condition. Active taVNS also decreased the difference between the pre- and post-tests in the power spectral density of spontaneous high-α band oscillations at C4 electrode. Importantly, parallel mediation models for right-hand responses showed that the change of P3 amplitude mediated the effects of taVNS on RT and IIRTV. In contrast, the change of MRCP amplitude suppressed the effect of taVNS on the IIRTV. Conclusions: Our results provided behavioural and brain evidence supporting the effects of taVNS on different attentional systems, and their interaction further shaped behavioural performance, suggesting a promising role of taVNS in cognitive enhancement.
ABSTRACT
Introduction: Virtual reality (VR) and transcutaneous electrical nerve stimulation (TENS) have emerged as effective interventions for pain reduction. However, their standalone applications often yield limited analgesic effects, particularly in certain painful conditions. Aims: Our hypothesis was that the combination of VR with TENS in a synchronous manner could produce the best analgesic effect among the four experimental conditions. Methods: To address this challenge, we proposed a novel pain modulation strategy that synchronously combines VR and TENS, aiming to capitalise on both techniques' complementary pain modulation mechanisms. Thirty-two healthy subjects participated in the study and underwent three types of interventions: VR alone, a combination of VR with conventional TENS, and a combination of VR with synchronous TENS. Additionally, a control condition with no intervention was included. Perceived pain intensity, pain unpleasantness, positive and negative affect scores, and electroencephalographic (EEG) data were collected before and after the interventions. To delve into the potential moderating role of pain intensity on the analgesic efficacy of VR combined with synchronous TENS, we incorporated two distinct levels of painful stimuli: one representing mild to moderate pain (ie, low pain) and the other representing moderate to severe pain (ie, high pain). Results: Our findings revealed that both combination interventions exhibited superior analgesic effects compared with the VR-alone intervention when exposed to low and high pain stimuli. Notably, the combination of VR with synchronous TENS demonstrated greater analgesic efficacy than the combination of VR with conventional TENS. EEG data further supported these results, indicating that both combination interventions elicited a greater reduction in event-related potential magnitude compared with the VR-alone intervention during exposure to low and high pain stimuli. Moreover, the synchronous combination intervention induced a more significant reduction in N2 amplitude than the VR-alone intervention during exposure to low pain stimuli. No significant differences in EEG response changes were detected between the two combination interventions. Both combination interventions resulted in a greater reduction in negative affect compared with the VR-alone intervention. Conclusions: Altogether, our study highlights the effectiveness of the synchronous combination of VR and TENS in enhancing pain modulation. These findings offer valuable insights for developing innovative pain treatments, emphasising the importance of tailored and multifaceted therapeutic approaches for various painful conditions.
ABSTRACT
PURPOSE OF REVIEW: Transcutaneous electrical nerve stimulation (TENS) is widely used as a non-pharmacological approach for pain relief in a variety of clinical conditions. This manuscript aimed to review the basic mechanisms and clinical applications regarding the use of TENS for alleviating the peripheral (PNP) and central neuropathic pain (CNP). RECENT FINDINGS: Basic studies on animal models showed that TENS could alleviate pain by modulating neurotransmitters and receptors in the stimulation site and its upper levels, including the spinal cord, brainstem, and brain. Besides, many clinical studies have investigated the efficacy of TENS in patients with CNP (caused by spinal cord injury, stroke, or multiple sclerosis) and PNP (induced by diabetes, cancer, or herpes zoster). Most clinical trials have demonstrated the efficacy of TENS in attenuating neuropathic pain and suggested that appropriate stimulation parameters (e.g., stimulation frequency and intensity) were critical to improving the analgesic effects of TENS. However, there are some conflicting findings related to the efficacy of TENS in relieving neuropathic pain. With optimized stimulation parameters, TENS would be effective in attenuating neuropathic pain. To obtain sufficient evidence to support the use of TENS in the clinic, researchers recommended performing multicenter clinical trials with optimized TENS protocols for the treatment of various CNP and PNP.
