Investigating Different Levels of Bimanual Interaction With a Novel Motor Learning Task: A Behavioural and Transcranial Alternating Current Stimulation Study

Abstract

Many tasks require the skilled interaction of both hands, such as eating with knife and fork or keyboard typing. However, our understanding of the behavioural and neurophysiological mechanisms underpinning bimanual motor learning is still sparse. Here, we aimed to address this by first characterising learning-related changes of different levels of bimanual interaction and second investigating how beta tACS modulates these learning-related changes. To explore early bimanual motor learning, we designed a novel bimanual motor learning task. In the task, a force grip device held in each hand (controlling x- and y-axis separately) was used to move a cursor along a path of streets at different angles (0°, 22.5°, 45°, 67.5°, and 90°). Each street corresponded to specific force ratios between hands, which resulted in different levels of hand interaction, i.e., unimanual (Uni, i.e., 0°, 90°), bimanual with equal force (Bieq, 45°), and bimanual with unequal force (Biuneq 22.5°, 67.5°). In experiment 1, 40 healthy participants performed the task for 45 min with a minimum of 100 trials. We found that the novel task induced improvements in movement time and error, with no trade-off between movement time and error, and with distinct patterns for the three levels of bimanual interaction. In experiment 2, we performed a between-subjects, double-blind study in 54 healthy participants to explore the effect of phase synchrony between both sensorimotor cortices using tACS at the individual’s beta peak frequency. The individual’s beta peak frequency was quantified using electroencephalography. 20 min of 2 mA peak-to-peak amplitude tACS was applied during task performance (40 min). Participants either received in-phase (0° phase shift), out-of-phase (90° phase shift), or sham (3 s of stimulation) tACS. We replicated the behavioural results of experiment 1, however, beta tACS did not modulate motor learning. Overall, the novel bimanual motor task allows to characterise bimanual motor learning with different levels of bimanual interaction. This should pave the way for future neuroimaging studies to further investigate the underlying mechanism of bimanual motor learning.

Relationship between skill training and skill transfer through the example of bimanual motor learning

“…In the beginning of the experiment, two questionnaires were completed online. Like Schoenfeld et al (2021), we used a short self‐report questionnaire with scores from 1 (basic) to 3 (expert) to estimate bimanual competence, comprising a range of activities including sports, hobbies, keyboard and phone typing, musical instruments and video games. Additionally, participants completed the short version of the achievement motivation inventory AMI (translated from German ‘Leistungsmotivationsinventar’, Schuler & Prochaska, 2001), a psychological test inventory measuring different aspects of work‐related achievement motivation.…”

“…All five training tasks were performed for 100 trials (see Schoenfeld et al, 2021 for a discussion on a number of repetitions versus time of training), thus the actual time on task was comparable across the five training tasks. Each trial equalled one path comprising six streets (Figure 1b).…”

“…The task used here was inspired by Doost et al (2017), who adapted a bimanual version of a circuit game from Lefebvre et al (2012) to study bimanual motor learning with equal contributions of hands. We believe the task used here is particularly well-suited for this question as it can be easily adapted in several ways to create sets of training and transfer tasks and it reliably induces learning (Schoenfeld et al, 2021). Motor learning, both bimanual and unimanual, implies motor skill acquisition through repetition and training, which results in lasting improvements in speed and accuracy (Willingham, 1998).…”

“…Secondly, the identical elements theory suggests a positive relationship between the amount of transfer and the similarity between the training and transfer task (Lee, 1988; Magill & Anderson, 2014; Thorndike & Woodworth, 1901). For instance, transfer occurred when the training and transfer task only differed in speed, distance to target and muscles involved (Aune et al, 2017; Keetch et al, 2005; Shea & Kohl, 1990; Simons et al, 2009), but was absent when performing drawing instead of tapping, a new movement sequence or the control‐display relationship was reversed, i.e., transposition (Grafton et al, 2002; Lewis et al, 1951; Robertson et al, 1999; Schoenfeld et al, 2021).…”

“…To explore the relationship between training and transfer we use a task probing bimanual motor learning recently published by Schoenfeld et al (2021). Bimanual motor tasks require the interaction of both hands and have experimentally studied with finger tapping and flexion/extensions tasks (e.g., Aoki et al, 2003; Bangert et al, 2010; Debaere et al, 2004; Kajal et al, 2017; Serrien, 2008), cyclic/rhythmic tasks (e.g., Mueller et al, 2009; Preilowski, 1972; Sisti et al, 2011) and cooperative tasks (e.g., Doost et al, 2017).…”