  Neural correlates of movement planning onset and direction may be present in
human electrocorticography in the signal dynamics of both motor and non-motor
cortical regions. We use a three-stage model of jPCA reduced-rank hidden Markov
model (jPCA-RR-HMM), regularized shrunken-centroid discriminant analysis (RDA),
and LASSO regression to extract direction-sensitive planning information and
movement onset in an upper-limb 3D isometric force task in a human subject.
This mode achieves a relatively high true positive force-onset prediction rate
of 60% within 250ms, and an above-chance 36% accuracy (17% chance) in
predicting one of six planned 3D directions of isometric force using
pre-movement signals. We also find direction-distinguishing information up to
400ms before force onset in the pre-movement signals, captured by electrodes
placed over the limb-ipsilateral dorsal premotor regions. This approach can
contribute to more accurate decoding of higher-level movement goals, at earlier
timescales, and inform sensor placement. Our results also contribute to further
understanding of the spatiotemporal features of human motor planning.
