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Electrotactile stimulus is a form of sensory substitution in which an electrical signal is perceived as a mechanical sensation. The electrotactile effect could, in principle, recapitulate a range of tactile experience by selective activation of nerve endings. However, the method has been plagued by inconsistency, galvanic reactions, pain and desensitization, and unwanted stimulation of nontactile nerves. Here, we describe how a soft conductive block copolymer, a stretchable layout, and concentric electrodes, along with psychophysical thresholding, can circumvent these shortcomings. These purpose-designed materials, device layouts, and calibration techniques make it possible to generate accurate and reproducible sensations across a cohort of 10 human participants and to do so at ultralow currents (≥6 microamperes) without pain or desensitization. This material, form factor, and psychophysical approach could be useful for haptic devices and as a tool for activation of the peripheral nervous system. 

A roadmap of the spine During spinal cord surgery, intraoperative neuromonitoring (IONM) is used to reduce the risk of damage. Electrodes on muscles or scalp record the response to large-amplitude electrical stimuli delivered to the spinal cord. However, this method does not allow precise spatiotemporal characterization of spinal cord neurophysiology. Now, Russman et al. developed a microelectrode array that can be placed on the spinal cord during surgery and record with high spatiotemporal definition and high sensitivity the electrophysiological response to low-current stimulation, providing precise maps of spinal cord electrophysiology. These maps can be used during surgery to improve IONM. 

Cortex in high resolution Recording brain cortical activity with high spatial and temporal resolution is critical for understanding brain circuitry in physiological and pathological conditions. In this study, Tchoe et al. developed a reconfigurable and scalable thin-film, multithousand-channel neurophysiological recording grids using platinum nanorods, called PtNRGrids, that could record thousands of channels with submillimeter resolution in the rat barrel cortex. In human subjects, PtNRGrids were able to provide high-resolution recordings of large and curvilinear brain areas and to resolve spatiotemporal dynamics of motor and sensory activities. The results suggest that PtNRGrids could be used in the preclinical and clinical setting for high spatial and temporal recording of neural activity.