Fig. 6. Passive observation and brain control paradigms.

(A) A monkey was seated in front of a screen with both arms gently restrained and covered by an opaque material during passive observation and BC without arms experiments. (B) Actual left and right arm X-position (black) compared with predicted X-position (red) for passive observation sessions. Pearson’s correlation, r, is indicated. (C) Performance of monkey C (left) and monkey M (right) quantified as fraction correct trials. Shown separately for monkey C are different decoding model parameter settings (red, blue markers) as well as brain control without arm movement sessions (black, both monkeys). Sessions with less than 10 attempted trials were set to zero due to insufficient data (open circles). (D) Fraction of trials where the left arm (green circles) and right arm (blue circles) acquired their respective target during brain control. Linear fit for learning trends of each paradigm is shown as in (C). (E–F) Fraction of correct predictions by k-NN of target location for each arm (blue/green) over the trial period during both passive observation (E) and brain control without arm movement (BC without arm movements) (F) in both monkey C (left column) and monkey M (right column). (G) Mean k-NN target prediction fraction correct from neuron dropping curves separated by cortical area for each monkey (same columns as E–F). UKF, unscented Kalman filter;