Cognitive control processes during balance and locomotion : walking an attentional tightrope

Abstract

The Theory of Reinvestment proposes that relatively automated motor performance can be disrupted by conscious step-by-step movement processing using previously acquired verbal knowledge. Movement specific reinvestment has been widely examined in ontogenetic motor skills (i.e., skills that extend fundamental movements for specialized purposes and must be deliberately learned), for which verbal knowledge is more readily available. Therefore, in five studies this thesis examined the role of movement specific reinvestment in young and older adults during phylogenetic motor skills (i.e., fundamental movements), balance and walking. It was found that movement specific reinvestment played a role in balance performance by young adults but not older adults (Chapters 2, 3, and 4). Specifically, young adults with a high propensity for reinvestment showed a more constrained, less complex, mode of balancing than young adults with a low propensity for reinvestment. However, verbally describing (overshadowing) balancing affected the performance of young adults with a low, but not a high, propensity for movement specific reinvestment. It was argued, that people with a high propensity for reinvestment, contrary to people with a low propensity, were accustomed to verbal processing and therefore were not affected by verbalization. It was further argued that movement specific reinvestment may not have played a role in balance performance by older adults because older adults did not possess, or could not access, verbal knowledge about their balancing. On the other hand, for older adults, an association was found between movement specific reinvestment, attention focus and visuo-motor control during walking in a demanding environment that required accurate stepping and navigation of obstacles (Chapters 5 and 6). Specifically, older adults with a high propensity for movement specific reinvestment compared to a low propensity for movement specific reinvestment showed greater awareness of their body movements and decreased awareness of the external environment during walking. Furthermore, they also displayed longer stance and double support times when approaching a stepping target and, subsequently, increased stepping error. It was argued that because of the tendency to engage in verbal processing, older adults with a high propensity for movement specific reinvestment needed more time to “plan” their stepping movements - this inefficient information processing lead to worse stepping accuracy. The findings of this thesis inform the Theory of Reinvestment and contribute to current understanding of the role of consciousness in phylogenetic motor skills.