Untangling the causes of interference during a random practice schedule


Motor learning involves a series of neurophysiological processes, regrouped under the term "consolidation" (McGaugh, 2000), which take place between practice sessions and are crucial for skill retention (Lohse et al., 2014; Walker, 2005). To optimize consolidation, recent results suggest that motor skills should be practiced in isolation from one another (Borragán et al., 2015; Krakauer & Shadmehr, 2006). Previous results from our laboratory supported this suggestion by showing that a random practice schedule can lead to anterograde interference (Neville & Trempe, SCAPPS 2014). Because interference is believed to occur when two tasks compete for shared resources in the brain (Ray et al., 2013), we hypothesized that this result was caused by a competition in networks either involved in movement execution and/or in acquiring the cognitive representation of the sequences. To test these two possibilities, participants learned to produce as fast and accurately as possible a 5-element sequence of fingers movements. Using a random practice schedule, participants also either typed random key presses (n = 12) or observed a novice model practice a different sequence of fingers movements (n = 11). When retention of the sequence was assessed 24 hours later, participants of both groups failed to demonstrate an increase in typing speed (p > . 26) or accuracy (p > .40) compared to their performance the day before, a result similar to what we reported when participants physically practiced two distinct sequences alternatively. Thus, our results suggest that the anterograde interference resulting from random practice has a cognitive and a motor origin.

Acknowledgments: This work was funded by NSERC through an Undergraduate Student Research Award (KM Neville)