## 1 Introduction  
Electrical stimulation can be used as a therapeutic tool to relieve bone disorder or neurological pain conditions. This approach can expand the size of the cortical receptor area and improve the sensitivity of the somatosensory system [1]. The transcutaneous application of electrical current activates neurons, which in turn can lead to physiological changes such as enhanced blood circulation and muscle activity through increased muscle metabolism [2]. Therefore, electrical stimulation has been reported to be effective in controlling pain, retraining and strengthening muscles, and healing wounds [3]. However, the stimulation of peripheral sensory receptors that affect the excitatory state of the motor cortex can differ depending on the type of electrical stimulation applied and the time of intervention [4]. In addition, in the absence of established indicators, there is a tendency to evaluate the various therapeutic effects of electrical stimulation according to the patient's pain intensity, so applying an appropriate level of electrical stimulation is a difficult task [5]. Thus, many studies from different fields have emphasized the necessity for an effective clinical approach based on current stimulation tailored to each patient's specific needs [6]. The use of computers enables visual judgments and quantitative mathematical analyses of the state of brain function and makes it possible to analyze brain function objectively [7]. Electroencephalographyhas been used to objectively evaluate the variability of the current thresholds and the adaptation of peripheral nerves induced by electrical stimulation [8]. By measuring cortical electrical activity, these tests can objectively control the variable current threshold, thus modifying the peripheral nerve induction by electrical stimulation. The increased excitability of nerve cells due to physical stimulation may also increase muscular motor-evoked potentials [9]. Thus, electroencephalogram patterns representing changes in electrical signals between brain neuronal cells are widely used as diagnostic indicators in various fields of medicine [10]. The electrical waveforms of electroencephalography are a means for the cerebral cortex to maintain contact with the rest of the body and allow the processing of external information for comparison, analysis, judgment, and decision making [11]. During tasks requiring concentration, the frontal lobe is involved in memory encoding and planning resulting from current actions. The parietal lobe is involved in the reception and processing of sensory information from the body [6]. By revealing brain activity and activation states, which are regulated by a balance between central and peripheral organs, the existence of distinct patterns affected by the brain's conscious condition, mental activity, pathology, and electrical stimulation may be confirmed [12]. Interferential current (IFC) stimulation is an intervention method combining the advantages of high permeability from middle-frequency currents and efficient tissue stimulation from low-frequency currents [13]. IFC stimulation has a much shorter pulse duration than transcutaneous nerve stimulation and, therefore, can deliver maximum current to tissues with high tissue permeability. Thus, this intervention can be applied in various clinical settings due to its physiological mechanism of deep current permeation into a specific area of the body during current conduction [3]. In patients with symptoms of hypertonicity in the spinal erector muscle or imbalance in the autonomic nervous system, electrical stimulation methods are used, modifying the amplitude modulation frequency and waveform through electrode placement to the paravertebral area [14]. Human tissue comprises cells suspended in an aqueous medium, making its electrical conductivity inhomogeneous on a microscopic scale [15]. Therefore, the acquired electroencephalography response patterns to maximum electrical stimulation are reportedly various and irregular [10].