Avaliação neuro-psicofisiológica de protocolos de estimulação eletrotátil para feedback sensorial

Abstract

The irreversive lession of a complex system like the human hand results in devastating losses of autonomy and functionality, which are attempted to be overcome through the use of prosthetic systems. However, despite various advancements in prosthetic development, rejection rates remain high. Among the most evident aspects explaining this phenomenon are the lack of functionality and the absence of a sensory feedback system capable of providing the user with tactile information from the interaction of the prosthesis with the environment and surrounding objects. In non-invasive tactile restoration, transcutaneous electrical nerve stimulation (TENS) is commonly used to evoke tactile sensations, particularly those referred to as phantom limbs. Despite its widespread use, there is no consensus on stimulation parameters capable of eliciting a wide range of natural sensations or even protocols for its evaluation. The present study aimed to combine psychophysiological and cortical imaging techniques to provide a qualitative and quantitative analysis of somatosensory perception processes. For this purpose, the study conducted two experimental designs composed of: i) psychophysiological evaluation of incremental and decremental changes in stimulation frequency (modulated between 5 and 125 Hz) while maintaining a constant amplitude, and ii) analysis of sensory quality and cortical responses from a protocol of discrimination of electro-tactile stimuli of five different frequencies (10, 25, 50, 100, and 125 Hz). The study involved 20 healthy individuals and 3 subjects with transradial upper limb amputation or wrist disarticulation. The results point to important findings, such as the use of amplitudes around 80% of the subject's pain threshold to evoke sensations referred to the phantom limb. The study also indicates a relationship between subjective descriptors of tactile perception and evoked neural responses, which were also effective in feeding a support vector machine (SVM) that efficiently distinguished the electrodermal stimuli. The use of the P300 potential as a biomarker for sensory perception evaluations and distinction of electrical stimuli is highlighted, for example. Therefore, this work presents important findings that can be used as a starting point for the development of sensory feedback systems, as well as highlighting the individual distinctions of each subject that should be considered for the creation of robust, efficient, and comfortable systems.