Healthy aging impairs the ability to adapt movements to novel situations and to switch choices according to the context in cognitive tasks, indicating resistance to changes in motor and cognitive behaviors. Here we examined if this lack of “flexibility” in old subjects observed in motor and cognitive domains were related. To this end, we evaluated subjects' performance in a motor task that required switching walking patterns and its relation to performance in a cognitive switching task. Specifically, a group of old (>73 years old) and young subjects learned a new locomotor pattern on a split-belt treadmill, which drives the legs at different speeds. In both groups, we assessed the ability to disengage the walking pattern learned on the treadmill when walking overground. Then, we determined if this motor context-specificity was related to subjects' cognitive ability to switch actions in a set-shift task. Motor and cognitive behaviors were tested twice on separate visits to determine if age-related differences were maintained with exposure. Consistent with previous studies, we found that old adults adapted slower and had deficits in retention. Most importantly, we found that older subjects could not switch locomotor patterns when transitioning across walking contexts. Interestingly, cognitive switching performance was inversely related to subjects' ability to switch walking patterns. Thus, cognitive mediated switching interfered with locomotor switching. These findings were maintained across testing sessions. Our results suggest that distinct neural substrates mediate motor and cognitive action selection, and that these processes interfere with each other as we age.

Generalization of movements from experienced to novel situations is a critical aspect of motor learning. It has been demonstrated that the training period when a movement is learned influences the movement's generalization to untrained situations. However, little is known about how healthy aging affects these processes. For example, young adults exhibit greater generalization of movements learned on a device (e.g. split-belt treadmill or robotic arm) to movements without it (e.g, overground walking or unconstrained reaching) when participants experience small vs. large perturbations on the training device. Here, we investigated whether a similar effect would be observed in older adults. To this end, we compared the generalization of split-belt adaptation to overground walking in older (75.9 +/- 4.8 years old) and young adults (24.7 +/- 5.9 years old) when adapted gradually (i.e., small perturbations) vs. abruptly (i.e., large perturbations). We found that both age groups adapted more to the abrupt condition compared to the gradual condition, which resulted in greater adaptation effects (i.e., aftereffects) on the treadmill in the abrupt than the gradual groups. We also found that older adults generalize more than young adults, regardless of the perturbation schedule (i.e., gradual or abrupt). Our results suggest that abrupt perturbations during adaptation do not limit the generalization of movement in older adults -perhaps because they are more likely to attribute them to their own faulty movements. These results suggest that large perturbations are better than small when training older clinical populations since abrupt disturbances would lead to more adaptation and generalization of corrected movements in older people.