## 1 Introduction  
Transcutaneous electrical acupuncture (or 'acupoint') stimulation (TEAS) represents a significant advancement in integrative medicine, merging the principles of traditional acupuncture with modern electrical stimulation techniques. TEAS involves the application of electrical currents to acupuncture points on the skin surface, offering a non-invasive alternative to traditional manual acupuncture (MA) and electroacupuncture (EA) [1]. Thistechnique has garnered increasing attention for its potential therapeutic benefits, particularly in enhancing recovery and managing pain following surgical procedures. TEAS is notable for its ability to stimulate specific acupoints without needle insertion, which reduces the risk of infection and discomfort, making it a preferable option for many patients. Recent studies have highlighted the efficacy of TEAS in various clinical applications. [PERSON] et al. (2024) conducted a meta-analysis demonstrating that TEAS significantly improves postoperative recovery quality, as measured by Quality of Recovery-40 (QoR-40) scores, and that it reduces postoperative pain and nausea [2]. Similarly, another systematic review by [PERSON] et al. (2024) confirmed the effectiveness of TEAS in improving sleep quality and managing insomnia, especially in postoperative patients [3]. Additionally, [PERSON] et al. (2023) demonstrated that TEAS effectively prevents postoperative nausea and vomiting (PONV) in high-risk patients undergoing laparoscopic gynecological surgery, reducing postoperative abdominal distension and pain, and improving overall recovery quality [4]. The safety profile of TEAS is well documented, with minimal adverse effects reported. [PERSON] et al. (2024) emphasized the method's safety in a meta-analysis, noting that TEAS not only improves postoperative QoR-40 scores but also reduces the incidence of postoperative nausea and vomiting without significant adverse reactions [2]. Moreover, the non-invasive nature of TEAS makes it suitable for patients who are contra-indicated for traditional acupuncture, due to needle phobia or bleeding disorders. Further supporting these findings, [PERSON] et al. (2021) demonstrated the efficacy of TEAS in alleviating catheter-related bladder discomfort and improving overall postoperative comfort in patients undergoing transurethral resection of the prostate [5]. Moreover, [PERSON] et al. (2018) found that TEAS improved the quality of recovery during the early period after laparoscopic cholecystectomy [6]. These studies collectively underscore the broad applicability and safety of TEAS in various surgical contexts. Investigation into the brain's specific reactions to acupuncture has garnered significant interest in recent times. Advanced neuroimaging tools, such as electroencephalogram (EEG) and functional magnetic resonance imaging (fMRI), have been extensively employed to unravel acupuncture's underlying processes. Researchers have utilized fMRI to explore how acupuncture modulates brain activities and to distinguish the effects elicited by various genuine and sham acupuncture points [7]. The physiological and psychological impacts of TEAS are influenced by various stimulus parameters, including the choice of acupuncture points, the intensity of stimulation, and the frequency at which stimulation is applied [8; 9; 10]. Research indicates that both low- and high-frequency stimulation are effective for analgesia, but through different mechanisms [11]. Low-frequency (2-4 Hz), high-intensity electrical stimulation resulting in muscle contractions and a sustained analgesic effect are particularly beneficial for neuropathic pain relief compared to high-frequency stimulations [12]. Conversely, high-frequency stimulation at low intensity is associated with muscle relaxation, which may also contribute to its analgesic properties [13]. [PERSON] et al.