A portable closed-loop platform enabling cortical evoked potential operant conditioning: system development and validation of target intensity estimation.

This study presents customizations and evaluations aimed at adapting a closed-loop platform designed for cortical evoked potential operant conditioning into a portable, user-friendly platform for real-time neurofeedback applications. Such applications can be useful for development of novel sensory and motor evoked response feedback approaches for rehabilitating lost function due to a brain or spinal injury. The current version of this system is component-heavy, and our primary goal was to reduce its footprint by integrating components, while supporting quality data acquisition, and without compromising real-time feedback. One key limitation in transitioning to a portable and integrated biosignal acquisition system is their typically lower sampling rates (e.g. 300-600 Hz) compared to high-resolution systems (e.g. 3200 Hz), typically used for detecting transient muscle and reflex responses (H-reflex andM-wave) for generating their recruitment curves. These are an essential part of the closed-loop platform, important for minimizing intra- and inter-session variability in effective afferent excitation. We evaluate whether lower-resolution signals would be usable in this setup. We find that despite larger dispersion of data, as expected, they can still provide comparable estimates of recruitment curve-based key components, as the higher-resolution counterparts. We also demonstrate the usability of automated response delineation under these lower sampling conditions, important in objectively analyzing post-injury data. Overall, this study demonstrates the feasibility of a portable/compact closed-loop system that enables real time feedback based on brain and muscle evoked responses. It also offers practical recommendations for selecting acquisition hardware to support reliable signal quality, real-time processing, and portability for this setup. Next, we aim to test it in a larger patient cohort, under non-laboratory settings.