Divided Attention Impairs Human Motor Adaptation But Not Feedback Control

Abstract

When humans experience externally induced errors in a movement, the motor system's feedback control compensates for those errors within the movement. The motor system's predictive control then uses information about those errors to inform future movements. The role of attention in these two distinct motor processes is unclear. Previous experiments have revealed a role for attention in motor learning over the course of many movements; however, these experimental paradigms do not determine how attention influences within-movement feedback control versus across-movement adaptation. Here we develop a dual-task paradigm, consisting of movement and audio tasks, which can differentiate and expose attention's role in these two processes of motor control. Over the course of several days, subjects performed horizontal reaching movements, with and without the audio task; movements were occasionally subjected to transient force perturbations. On movements with a force perturbation, subjects compensated for the force-induced movement errors, and on movements immediately after the force perturbation subjects exhibited adaptation. On every movement trial, subjects performed a two-tone frequency-discrimination task. The temporal specificity of the frequency-discrimination task allowed us to divide attention within and across movements. We find that divided attention did not impair the within-movement feedback control of the arm, but did reduce subsequent movement adaptation. We suggest that the secondary task interfered with the encoding and transformation of errors into changes in predictive control.

Trial-by-Trial Transformation of Error Into Sensorimotor Adaptation Changes With Environmental Dynamics

“…Current state-space models presume proportionality and have successfully mimicked human behavior Smith et al 2006;Thoroughman and Shadmehr 2000;Thoroughman and Taylor 2005). One study explicitly showed proportionality when forces were strongly biased and presented in every trial (Scheidt et al 2001).…”

“…2). Previous models Scheidt et al 2001;Smith et al 2006;Thoroughman and Shadmehr 2000;Thoroughman and Taylor 2005) presumed proportionality and therefore could not account for alternative strategies. Here, we modeled adaptation using a set of state-space equations that did not explicitly presume proportionality.…”

“…Recently, studies of motor learning have used system identification, coupled with adapting basis function networks, to quantify adaptation across single movements and the generalization of that adaptation to neighboring movement directions Hwang et al 2003;Thoroughman and Shadmehr 2000;Thoroughman and Taylor 2005). Thoroughman and Shadmehr (2000) suggested that modifications to interneuronal connections are proportional to motor error and gated by the velocity-tuned activity of individual presynaptic neurons.…”

Thinking About Walking: Effects of Conscious Correction Versus Distraction on Locomotor Adaptation

“…This automaticity of tasks has been studied with dual-task paradigms in learning novel skills, motor adaptations, sensory discrimination tasks, and walking (Collette et al 2005;Lang and Bastian 2002;Taylor and Thoroughman 2007;Yogev-Seligmann et al 2008). Dual-tasking requires subjects to complete unrelated tasks simultaneously, which involves the coordination and integration of different processing mechanisms (Collette et al 2005).…”

“…Although healthy adults can complete dual tasks, there is still a detrimental effect on performance-they make more errors and take longer to learn the skill of interest (Collette et al 2005;Lang and Bastian 2002). Taylor and Thoroughman hypothesized that a secondary task can interfere with feed-forward mechanisms of error correction (Taylor and Thoroughman 2007), which could result in more errors and a slower learning rate. To our knowledge, the effects of dual-tasking on the adaptation of an automatic task, like walking, have not been studied.…”