Figure 9.

Patterns of muscle activity for leg movement (step) and contralateral support (stand) as measured by ER-EMG traces are influenced by task congruency and performance. (A–D) All congruent trial response (A,B) and incongruent trial response (C,D) showed distinct and lateralized EMG patterns in the early-stage up to 300 ms post-stimulus onset. In all cases, lateralization reflected location information in the Simon trial. (E–H) In contrast, ER-EMG patterns for irrelevant responses were rather complex. (E) In congruent trials, responses showed that a maintained goal-relevant pattern up to around 600 ms followed by a sudden inversion leading to irrelevant responses. The irrelevant responses for the other conditions (F–H) exhibited similar patterns compared to relevant responses. (I) ER-EMG trace difference between step and support (stand) sides represented the APA for stepping. The irrelevant APAs were reversed at around 300 ms for response correction. (J) In contrast, the irrelevant APAs were not corrected. (K) The ER-EMG trace recorded during NC condition showed to lateralization or reversal in the early-stage. (L) The difference between step and support sides became substantial only after ~300 ms, implying that automatic processing was not recruited in the effortless NC task.