Mechanisms within the Parietal Cortex Correlate with the Benefits of Random Practice in Motor Adaptation

Abstract

The motor learning literature shows an increased retest or transfer performance after practicing under unstable (random) conditions. This random practice effect (also known as contextual interference effect) is frequently investigated on the behavioral level and discussed in the context of mechanisms of the dorsolateral prefrontal cortex and increased cognitive efforts during movement planning. However, there is a lack of studies examining the random practice effect in motor adaptation tasks and, in general, the underlying neural processes of the random practice effect are not fully understood. We tested 24 right-handed human subjects performing a reaching task using a robotic manipulandum. Subjects learned to adapt either to a blocked or a random schedule of different force field perturbations while subjects’ electroencephalography (EEG) was recorded. The behavioral results showed a distinct random practice effect in terms of a more stabilized retest performance of the random compared to the blocked practicing group. Further analyses showed that this effect correlates with changes in the alpha band power in electrodes over parietal areas. We conclude that the random practice effect in this study is facilitated by mechanisms within the parietal cortex during movement execution which might reflect online feedback mechanisms.

Neural Mechanisms of the Contextual Interference Effect and Parameter Similarity on Motor Learning in Older Adults: An EEG Study

“…The purpose of this study was to investigate the neural mechanisms of CIE and parameter similarity on motor learning in older adults. The results of this study confirmed the previous findings of other studies demonstrating that high CI (random practice) can increase the activities of cognitive, sensory, and motor regions of the brain compared to blocked practice (Cross et al, 2007;Lin et al, 2008Lin et al, , 2010Lin et al, , 2013Cohen et al, 2009;Wymbs and Grafton, 2009;Thürer et al, 2017;Henz et al, 2018). The older adults also benefit from the high CI in reducing their error during the retention test and also their cognitive, sensory, and motor areas activated more than blocked practice.…”

“…Therefore, it is likely that there are different neurological paths in younger adults compared to older counterparts, to perform a motor task (Lin et al, 2012). Given that the CIE influences motor learning, it, therefore, can be concluded that it also affects brain activities associated with effort and motor preparation (Lage et al, 2015;Frömer et al, 2016;Thürer et al, 2017;Henz et al, 2018). Some studies have shown that CIE is associated with dorsolateral prefrontal cortex (DLPFC) and primary motor area (M1) activity (Cohen et al, 2009;Wymbs and Grafton, 2009;Kantak et al, 2010;Lin et al, 2010;Lage et al, 2015).…”

Contextual Interference Effect Is Independent of Retroactive Inhibition but Variable Practice Is Not Always Beneficial

“…This study focuses on motor adaptation using a force field paradigm (Shadmehr and Mussa-Ivaldi, 1994), for which retroactive inhibition has already been demonstrated (Brashers-Krug et al, 1996; Thürer et al, 2016). In addition, previous studies from our laboratory were able to show CIE with such a paradigm (Thürer et al, 2017, 2018b). In these studies, subjects had to adapt their reaching movements to different force field magnitudes either in a blocked or random fashion.…”

Contextual interference effect is independent of retroactive inhibition but variable practice is not always beneficial

“…We will briefly describe the experimental task which can be found elsewhere in more detail (Thürer et al, 2017). Participants were seated in front of the manipulandum and the virtual reality display was calibrated to the robot’s handle.…”

“…In contrast, motor adaptation is interpreted as a different type of motor learning, in which the motor system responds to changes in environmental conditions and/or changes in the body to regain the former capacity for a skilled movement under these new conditions (Krakauer & Manzoni, 2011). This study focuses on motor adaptation using a force field paradigm (Shadmehr & Mussa-Ivaldi, 1994), for which CIE has been demonstrated in previous studies from our laboratory (Thürer et al, 2017; Thürer & Weber et al, 2018). In these studies, subjects had to adapt their reaching movements to different force field magnitudes either in a blocked or random fashion.…”