###### Abstract  
The field of signal processing using machine and deep learning algorithms has undergone significant growth in the last few years, with a wide scope of practical applications for electroencephalography (EEG). Transcutaneous electroacupuncture stimulation (TEAS) is a well-established variant of the traditional method of acupuncture that is also receiving increasing research attention. This paper presents the results of using deep learning algorithms on EEG data to investigate the effects on the brain of different frequencies of TEAS when applied to the hands in 66 participants, before, during and immediately after 20 min of stimulation. Wavelet packet decomposition (WPD) and a hybrid Convolutional Neural Network Long Short-Term Memory (CNN-LSTM) model were used to examine the central effects of this peripheral stimulation. The classification results were analysed using confusion matrices, with _kappa_ as a metric. Contrary to expectation, the greatest differences in EEG from baseline occurred during TEAS at 80 pulses per second (pps) or in the'sham' (160 pps, zero amplitude), while the smallest differences occurred during 2.5 or 10 pps stimulation (mean _kappa_ 0.414). The mean and CV for _kappa_ were considerably higher for the CNN-LSTM than for the Multilayer Perceptron Neural Network (MLP-NN) model. As far as we are aware, from the published literature, no prior artificial intelligence (AI) research appears to have been conducted into the effects on EEG of different frequencies of electroacupuncture-type stimulation (whether EA or TEAS). This ground-breaking study thus offers a significant contribution to the literature. However, as with all (unsupervised) DL methods, a particular challenge is that the results are not easy to interpret, due to the complexity of the algorithms and the lack of a clear understanding of the underlying mechanisms. There is therefore scope for further research that explores the effects of the frequency of TEAS on EEG using AI methods, with the most obvious place to start being a hybrid CNN-LSTM model. This would allow for better extraction of information to understand the central effects of peripheral stimulation. transcutaneous electroacupuncture; sham stimulation; EEG; wavelet packet decomposition; machine learning; deep learning; CNN-LSTM; confusion matrix; AI +
Footnote †: journal: Medical Engineering, Izmir Katip Celebi Universitesi, Izmir 35620, Turkey 1  
clinical practice, most commonly for pain management and in a range of musculoskeletal presentations, predominantly in China [2]. TEAS has also been shown, for example, to be effective in the treatment of stroke [3], post-operative nausea and vomiting [4], and for improving symptoms of insomnia and anxiety in opioid use disorder [5]. In contrast to classical acupuncture, TEAS does not involve any puncture of the skin or the use of any needles. It is therefore potentially advantageous for any patient who has a fear of needles (so-called needle phobia) or for whom skin puncture might be considered an unacceptable clinical risk. [PERSON] et al. (1998) [6] identified that the effects of classic electroacupuncture (via needles) are stronger and more profound than those achieved with manual acupuncture (employing a needle but with no electrical stimulation). Furthermore, electroacupuncture with surface electrodes was demonstrated to be as effective as needle-based electroacupuncture. In functional magnetic resonance imaging (fMRI) studies, electroacupuncture has been shown to generate more widespread cerebral and sub-cortical changes than manual acupuncture [7; 8], and thus, the use of TEAS may have real physiological advantages over classical manual acupuncture. The safety concerns associated with acupuncture [9], although largely theoretical, can be ameliorated through the use of a surface electrode stimulating system (i.e., TEAS). The potential for home-based, patient-delivered acupuncture may have significant advantages (reduced cost, and a lower clinical burden for both the patient and the clinician).