Evaluation of Evoked Potentials Features During Electrodermal Stimulation for Somatosensory Feedback Protocols

Despite the advances in prosthesis development, the rate of abandonment remains high, and one of the main reasons is the lack of tactile sensory feedback. Transcutaneous nerve electrostimulation (TENS) is commonly used to provide somatotopic tactile information. However, there is still no consensus as to the best method of modulating its parameters or how to quantitatively assess differences in sensory perception. The aim of this paper is to quantitatively assess differences in sensory perceptions through the study of the N200 and P300 response as possible biomarkers for the classification of different frequencies of electrodermal stimulation and to evaluate the sensory perceptions of volunteers. Four volunteers participated in an electrodermal stimulation protocol with three stimulus frequencies (10, 50, and 125 Hz) applied to the left and right index fingers. Electroencephalographic (EEG) signals were acquired on 20 electrodes during the experiments. Individual and grand-averaged cortical responses were analyzed and exhibited alterations for the different experimental conditions. The amplitude and latency of the N200 and P300 evoked potentials were extracted from the EEG and used as attributes for a Support Vector Machine (SVM), to assess the ability of such potentials to distinguish the different stimuli. The results showed that the SVM was able to classify the different stimuli with an average accuracy of over 85%, demonstrating that the evoked potentials can be used as a quantitative metric to access the electrotactile perceptions. This evidenced the use of both potentials for the complete analysis of the cortical response for the distinction of tactile sensations.