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Over the last decades, conventional transcutaneous electrical nerve stimulation (TENS) has been utilized as an efficient rehabilitation intervention for alleviation of chronic pain, including phantom limb pain (PLP). However, recently the literature has increasingly focused on alternative temporal stimulation patterns such as pulse width modulation (PWM). While the effect of non-modulated high frequency (NMHF) TENS on somatosensory (SI) cortex activity and sensory perception has been studied, the possible alteration following PWM TENS at the SI has not yet been explored. Therefore, we investigated the cortical modulation by PWM TENS for the first time and conducted a comparative analysis with the conventional TENS pattern. We recorded sensory evoked potentials (SEP) from 14 healthy subjects before, immediately, and 60 min after TENS interventions (PWM and NMHF). The results revealed suppression of SEP components, theta, and alpha band power simultaneously associated with the perceived intensity reduction when the single sensory pulses applied ipsilaterally to the TENS side. The reduction of N1 amplitude, theta, and alpha band activity occurred immediately after both patterns remained at least 60 min. However, the P2 wave was suppressed right after PWM TENS, while NMHF could not induce significant reduction immediately after the intervention phase. As such, since PLP relief has been shown to be correlated with inhibition at somatosensory cortex, we, therefore, believe that the result of this study provides further evidence that PWM TENS may also be potential therapeutic intervention for PLP reduction. Future studies on PLP patients with PWM TENS sessions is needed to validate our result.

Objective. Transcutaneous electrical nerve stimulation (TENS) has been suggested as a possible non-invasive pain treatment. However, the underlying mechanism of the analgesic effect of TENS and how brain network functional connectivity (FC) is affected following the use of TENS is not yet fully understood. The purpose of this study was to investigate the effect of high-frequency TENS on the alteration of functional brain network connectivity and the corresponding topographical changes, besides perceived sensations. Approach. Forty healthy subjects participated in this study. Electroencephalography (EEG) data and sensory profiles were recorded before and up to an hour following high-frequency TENS (100 Hz) in sham and intervention groups. Brain source activity from EEG data was estimated using the LORETA algorithm. In order to generate the functional brain connectivity network, the Phase Lag Index was calculated for all pair-wise connections of eight selected brain areas over six different frequency bands (i.e. δ, θ, α, β, γ, and 0.5–90 Hz). Main results. The results suggested that the FC between the primary somatosensory cortex (SI) and the anterior cingulate cortex, in addition to FC between SI and the medial prefrontal cortex, were significantly increased in the gamma-band, following the TENS intervention. Additionally, using graph theory, several significant changes were observed in global and local characteristics of functional brain connectivity in gamma-band. Significance. Our observations in this paper open a neuropsychological window of understanding the underlying mechanism of TENS and the corresponding changes in functional brain connectivity, simultaneously with alteration in sensory perception.

Conventional transcutaneous electrical nerve stimulation (TENS) has been reported to effectively alleviate chronic pain, including phantom limb pain (PLP). Recently, literature has focused on modulated TENS patterns, such as pulse width modulation (PWM) and burst modulation (BM), as alternatives to conventional, non-modulated (NM) sensory neurostimulation to increase the efficiency of rehabilitation. However, there is still limited knowledge of how these modulated TENS patterns affect corticospinal (CS) and motor cortex activity. Therefore, our aim was to first investigate the effect of modulated TENS patterns on CS activity and corticomotor map in healthy subjects. Motor evoked potentials (MEP) elicited by transcranial magnetic stimulation (TMS) were recorded from three muscles before and after the application of TENS interventions. Four different TENS patterns (PWM, BM, NM 40 Hz, and NM 100 Hz) were applied. The results revealed significant facilitation of CS excitability following the PWM intervention. We also found an increase in the volume of the motor cortical map following the application of the PWM and NM (40 Hz). Although PLP alleviation has been reported to be associated with an enhancement of corticospinal excitability, the efficiency of the PWM intervention to induce pain alleviation should be validated in a future clinical study in amputees with PLP.

Transcutaneous electrical nerve stimulation (TENS) has been reported to alleviate pain in chronic pain patients. Currently, there is limited knowledge how TENS affects can cause cortical neuromodulation and lead to modulation of non-painful and painful sensations. Our aim was therefore to investigate the effect of conventional, high-frequency TENS on cortical activation and perceived sensations in healthy subjects. We recorded somatosensory evoked potentials (SEPs) and perceived sensations following high-frequency TENS (100 Hz) in 40 healthy subjects (sham and intervention group). The effect of TENS was examined up to an hour after the intervention phase, and results revealed significant cortical inhibition. We found that the magnitude of N100, P200 waves, and theta and alpha band power was significantly suppressed following the TENS intervention. These changes were associated with a simultaneous reduction in the perceived intensity and the size of the area where the sensation was felt. Although phantom limb pain relief previously has been associated with an inhibition of cortical activity, the efficacy of the present TENS intervention to induce such cortical inhibition and cause pain relief should be verified in a future clinical trial.

Following amputation, almost two-thirds of amputees experience unpleasant to painful sensations in the area of the missing limb. Whereas the mechanism of phantom limb pain (PLP) remains unknown, it has been shown that maladaptive cortical plasticity plays a major role in PLP. Transcutaneous electrical nerve stimulation (TENS) generating sensory input is believed to be beneficial for PLP relief. TENS effect may be caused by possible reversing reorganization at the cortical level that can be evaluated by changes in the excitability of the corticospinal (CS) pathway. Excitability changes are dependent on the chosen stimulation patterns and parameters. The aim of this study was to investigate the effect of two TENS patterns on the excitability of the CS tract among healthy subjects. We compared a non-modulated TENS as a conventional pattern with pulse width modulated TENS pattern. Motor evoked potentials (MEPs) from APB muscles of stimulated arm (TENS-APB) and contralateral arm (Control-APB) were recorded. We applied single TMS pulses on two subjects for each TENS pattern. The results showed that both patterns increase the CS excitability, while the effects of the conventional TENS is stronger. However, the amplitude of MEPs from control-APB after TENS delivery remained almost the same.Clinical Relevance- The primary results revealed changes in the activity of CS pathway for both patterns. A future study on a larger population is needed to provide strong evidence on the changes in CS excitability. The evaluation part with more factors such as changes in intracortical inhibition (ICI) may be beneficial to find an optimal modulated TENS pattern to enhance pain alleviation process in PLP.

Attention and numeration are two phenomena in cognitive sciences of brain. As the effect and interaction that these two activities have on each other, the importance of detecting differences between two phenomena is shown more than ever. Someone believes that the relation between two brain cognitive activities (i.e. attention and numeration) is close to the extent that they are considered as one. In most of past works, the qualitative effect of numeration or extra mental task on attention is surveyed. The aim of this article is to clarify differences between two phenomena and the effect of extra mental activity (numeration) on visual top-down attention. For this purpose we separate P300 sources signal and their subcomponents to divide two classes (attention with numeration and pure attention). To do this, constrained blind source separation (CBSS) is used. The main method is to use Infomax algorithm that beside it, minimizing the difference between reference and estimated signal P300 and also subcomponents, P3a and P3b, are used as constrained term. The obtained result indicates that time of appearance and amplitude of estimated signal P300 and their subcomponent for two class are different. By doing paired t-test, best result for divided two cognitive activities, were obtained by amplitude of estimated p300 with P-value 0.01. To our knowledge, Seen from this aspect to this subject, is a new effort.

Paying attention to different pictures is related to complex information processing in the brain. Categorizing visual objects using the electroencephalogram (EEG) signal of subject along with paying attention to pictures, is properly possible. The aim of this paper is to analyze the mental signal in order to show the differences in cognitive patterns during paying attention to sets of different pictures. For this purpose, EEG signals which were recorded from 45 people were used. Brain signals are recorded over the on head using 8 active electrodes and based on standard 10–20. After the pre-processing, ERP signals were extracted into two classes according to attention to the human face and fruit images. Firstly, 4 types of features has been extracted from N170, P200, N200 and P300 components: (1) time features, (2) non-linear features, (3) statistical features and (4) frequency features. Then dimension of Properties were reduced by using different algorithms. New and innovative work in this paper is using various algorithms for reducing feature dimension such as t-test, t-SNE and kernel t-SNE and comparing their results with each other. Classification of 2 classes were done in order to recognize the differences using SVM and KNN classifiers. Secondly we reexamined this process by using combined features from multiple ERP components and obtained best result in this condition by t-SNE and SVM classifier with 85.5% accuracy.

Attention is amongst the high level cognitive task which is associated with complex process in the brain. But in almost all researches, this process is associated with a secondary task, (like numeration). Some believe that the link between these two cognitive activities (i.e. attention and numeration) in human brain is very close and intricate. However, the goal of this research is to evaluate the side effects of counting on visual attention in order to clarify the definition of Attention through brain signals. In previous related researches, only the qualitative impacts of counting have been dealt with and endeavor in this field is a new effort. We used a novel psychophysics task to explore the impact of this extra task on visual top-down attention. EEG was recorded during the task from 48 subjects in occipital, Parietal and frontal lobes. Target-locked ERPs for attention with and without numerating were constructed. Time features corresponding to P300 component were extracted for all eight channels separately. Common feature selection method and classifiers were employed to separate two classes (attention with numeration and pure attention). The results indicate that our task was capable of separation and some of the predefined ERP, time features are meaningful while attention is with numeration. As a result, we have introduced ERP features which belong to this separation and also determined the most relevant brain areas. To our knowledge, this is the first time that this quantitative separation is performed.