Fine grained two-dimensional cursor control with epidural minimally invasive brain-computer interface

Brain-computer interface (BCI) can assist paralyzed patients in controlling external devices and improve their quality of life. However, existing intracortical BCIs entail risks of infection and challenges of long-term stability. In this study, we report on a tetraplegic patient implanted with our newly developed wireless minimally invasive BCI, NEO, in which eight Pt-Ir electrodes were placed epidurally over the hand area of the right sensorimotor cortex to record field potentials. We found that epidural neural signals from the hand area simultaneously represented both contralateral and ipsilateral movements. The spatio-spectral patterns of different movements exhibited prominent distinctions, revealing a bilateral representation structure of limb movements. Moreover, when two limb effectors (e.g., hand and elbow) moved simultaneously, their neural patterns exhibited non-additive changes relative to single movements. Based on these findings, we proposed a fine grained bilateral single/dual-movement decoding scheme for two-dimensional target control, thereby extending the degrees of freedom (DoF) of minimally invasive BCI systems and enhancing the information transfer rate (ITR). In two-dimensional center-out and web-grid tasks, the system achieved mean Fitts ITRs of 36.7 bpm and 30.0 bpm, respectively, with hit rates exceeding 91%. Neural recordings remained stable for over 18 months, and the decoder maintained stable performance for over 6 months without recalibration, demonstrating the safety and reliability of long-term home use.