Reaching the cognitive-motor interface: Cognitive load diminishes arm choice efficiency and motor performance in neurotypicals and individuals with stroke

Daily life requires use of the arms for a variety of tasks under competing cognitive demands, such as reaching for objects in a visually-cluttered kitchen cabinet while holding a conversation. Prior studies have suggested that such demands may impact motor performance, including selection of the most efficient arm to use to reach to a target in a given location. The research conducted here expands upon prior studies by 1) examining the role of cognitive load in arm choice efficiency using a novel virtual reality paradigm designed to mimic the demands of real-life visual search, object selection, and reaching to targets, and 2) examining the impact of such demands on motor performance in individuals with stroke. To manipulate cognitive demand, we varied the semantic similarity of objects in the reaching space and the presence or absence of a secondary task. We hypothesized that cognitive load would modulate efficiency of arm choice and performance in both neurotypicals and individuals with stroke. The results showed reduced efficiency of arm choice for the stroke and neurotypical control groups under increased demand. Under cognitive load, participants with stroke also showed slower reach initiation, slower movements, increased reach curvature, and increased performance differences between the paretic and non-paretic arms. These data indicate that cognitive factors influence arm choice efficiency in naturalistic reaching tasks in neurotypical individuals, and both arm choice efficiency and motor performance in stroke. Efficiency and performance decrements under cognitive load may in turn influence reduced use of the paretic arm during daily activities.