Extended Data Fig. 4: EMG signals of 6 upper limb muscles (bicep, radialis flexor, radialis extensor, pectoralis, posterior deltoid, lateral deltoid).

Time zero, movement onset. One example condition (CW curl field applied to down reaches). Shaded area, s.e.m. across trials. a, EMG signals in before-learning, late-learning, error-clamp and late-washout blocks. Muscle activity did not show signs of muscle co-contraction during learning (red). Muscle activity during the preparatory period remained flat and around the same level across all blocks (two-sided rank-sum test: P < 0.0001 for comparing late-learning or error-clamp bicep activity with before-learning or late-washout bicep activity during the preparatory period; P > 0.3 for all the other pairs of comparison during the preparatory period). Muscle activity patterns in before-learning (black) and late-washout trials (blue) were very similar. Muscle activity patterns in late-learning (red) and error-clamp trials (purple) were very similar. b, EMG signals in before-learning (black) and error-clamp (purple) blocks did not show a uniform shift across all 12 reaching targets. For all six muscles, EMG activity after learning increased in some directions and decreased in other directions. Muscle activity of reaching to the target 135 degrees away from the trained target (i.e., far targets with almost no behavioural generalization, see Fig. 1c) in before-learning and error-clamp trials showed similar temporal patterns.

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