During walking, our legs are precisely coordinated to maintain a specific phase relationship and pattern of joint motion. In a companion study (Reisman et al. SFN 2004), we show that healthy adults adapt their walking pattern to account for a disruption in inter-limb coordination imposed by a split-belt treadmill. Specifically, some walking parameters change quickly with no training after-effects (e.g. stance times), while others adapt slowly and show strong negative after-effects (e.g. limb phasing). Here, we aimed to answer whether the integrity of the cerebral cortex is required for these adaptive changes. We studied nine children between age 6 and 18 with hemispherectomy (surgical removal of one cerebral hemisphere for intractable seizure disorders) and age-matched controls. Subjects walked with belts tied at fast and slow speeds, and then adapted to split belt walking for 10 minutes with their hemiplegic leg moving twice as fast as the other leg. After-effects were determined by comparing their walkin...