Advantages of EEG phase patterns for the detection of gait intention in healthy and stroke subjects

TL;DR

This study demonstrates that EEG phase patterns, specifically the phase of movement-related cortical potentials, enhance gait intention detection in both healthy and stroke subjects, potentially reducing calibration time for BCI systems.

Contribution

It is the first to investigate the use of MRCP phase features for gait intention detection and compares their effectiveness to amplitude features across different transfer conditions.

Findings

Phase features have higher signal-to-noise ratio than amplitude features.

Phase-based detectors are most accurate during session-specific calibration.

Combining phase and amplitude features maintains accuracy across sessions and subjects.

Abstract

One use of EEG-based brain-computer interfaces (BCIs) in rehabilitation is the detection of movement intention. In this paper we investigate for the first time the instantaneous phase of movement related cortical potential (MRCP) and its application to the detection of gait intention. We demonstrate the utility of MRCP phase in two independent datasets, in which 10 healthy subjects and 9 chronic stroke patients executed a self-initiated gait task in three sessions. Phase features were compared to more conventional amplitude and power features. The neurophysiology analysis showed that phase features have higher signal-to-noise ratio than the other features. Also, BCI detectors of gait intention based on phase, amplitude, and their combination were evaluated under three conditions: session specific calibration, intersession transfer, and intersubject transfer. Results show that the phase based detector is the most accurate for session specific calibration (movement intention was correctly detected in 66.5% of trials in healthy subjects, and in 63.3% in stroke patients). However, in intersession and intersubject transfer, the detector that combines amplitude and phase features is the most accurate one and the only that retains its accuracy (62.5% in healthy subjects and 59% in stroke patients) w.r.t. session specific calibration. Thus, MRCP phase features improve the detection of gait intention and could be used in practice to remove time-consuming BCI recalibration.