The effects of training time, sensory loss and pain on human motor learning

Abstract

This study determined, in humans, the effects of (i) the number of within-session task repetitions (72 or 144 over a period of 15 or 30 min, respectively) on the time course of motor learning in a long-term (seven consecutive daily motor-training sessions and a 1-week post-follow-up) novel tongue-task training regime and (ii) somatosensory manipulations (capsaicin-induced intra-oral pain or lidocaine-induced sensory loss of the tongue tip) on motor learning in a short-term (single motor-training session consisting of 72 within-session task repetitions over a period of 15 min) novel tongue-task training regime. Novel tongue-task training consisted of tracking a moving target box by generating a pre-set amount of tongue-protrusion force onto a force lever. Analysis of motor behaviour revealed (i) a higher within-session gain for the 30-min tongue-task training regime, but this difference did not differentially affect the time course of the overall motor performance or additional motor performance variables between the 15- and 30-min tongue-task training regimes in subsequent training sessions. (ii) somatosensory manipulations of the tongue tip reduced the gains in overall motor performance, and this reduced motor performance was mainly characterized by exaggerated undershoot errors and delayed reaction times for the lidocaine tongue-task training regime and exaggerated overshoot and undershoot errors as well as delayed reaction times for the capsaicin tongue-task training regime. It is concluded that extended within-session task repetitions do not facilitate additional long-term gains in overall motor performance and intra-oral sensory loss or pain hinders motor learning.

Tonic Pain Experienced during Locomotor Training Impairs Retention Despite Normal Performance during Acquisition

“…Figure 4 illustrates TA EMG activity time course for Day 1 force field exposure, showing that subjects from both groups rapidly increased their TA activity in response to the force field. They then gradually stabilized at a lower plateau of activity, as previously reported in control subjects, probably seeking the most cost-effective strategy to perform the task (Blanchette et al, 2011). The results of the ANOVA highlight this behavior with a main effect of Time (F (1,28) ϭ 8.822, p ϭ 0.006), but no effect of Group or Group ϫ Time interaction.…”

“…This approach is very similar to what is frequently used in motor learning studies performed during reaching (Krakauer and Mazzoni, 2011): a limb segment is deviated from its normal trajectory using a robotic device, thereby forcing the participant to modify his motor commands to compensate for the imposed deviation to return toward normal movement trajectory. Force field adaptation during gait shows similar features as reaching adaptation, including a gradual error reduction over several trials (here gait cycles; Lam et al, 2006;Noble and Prentice, 2006;Emken et al, 2007;Gordon and Ferris, 2007;Blanchette and Bouyer, 2009;Noel et al, 2009;Savin et al, 2010;Blanchette et al, 2011), significant aftereffects (Lam et al, 2006Noble and Prentice, 2006;Emken et al, 2007;Blanchette and Bouyer, 2009;Noel et al, 2009;Savin et al, 2010;Blanchette et al, 2011), catch trials effects (Lam et al, 2006;Noel et al, 2009), and next-day retention (Gordon and Ferris, 2007;Fortin et al, 2009).…”

“…1 B, C). Subjects were instructed to "fight the force to walk as normally as possible" (Blanchette et al, 2011). More details on the perturbation can be found in Blanchette et al (2011).…”

“…Mean TA activity during the stance-to-swing burst, which is the period of interest during the adaptation to the perturbation (Blanchette et al, 2011), was compared. A two-way repeated-measures ANOVA was performed to evaluate the between-group effect (Pain vs Control), and the within-group effects of Time (Late Baseline 1 vs Late Baseline 2) on TA EMG activity.…”

“…Capsaicin-induced pain has been shown to prevent improvement in performance within a single training session in a tongue tracking task (Boudreau et al, 2007(Boudreau et al, , 2010. In contrast, performance after training in a simple finger task was unaltered by local pain induced by hypertonic saline injection (Ingham et al, 2011).…”