Action preparation in grasping reveals generalization of precision between implicit and explicit motor processes

Asymmetric effects of graspable distractor disks on motor preparation of successive grasps: A behavioural and event-related potential (ERP) study

“…After a small distractor, in contrast, PRTs associated to pentapod grips involved only a relatively small cost with weak statistical support for a difference with the baseline. These results are very similar to those of Pisu et al (2020) and support the notion that seeing the distractor affected the preparation of the response for the test. This distractor effect, however, appears to be qualitatively different from classical visuomotor priming in that the observed cost for incongruent distractor-test pairs (which is predicted by visuomotor priming) is much larger for small disks after large distractors than for large disks after small distractors.…”

“…Specifically, we aimed to assess how an implicit motor representation might affect the preparation of an explicit successive grasp. If PRTs for grasping a target are modified by the presentation of incongruent distractors (as reported by Pisu et al, 2020), and if this effect occurs at the level of motor preparation (as hypothesized again by Pisu et al), then corresponding ERP modulations should be observed in R-LRP's, but not in S-LRP or P300 components.…”

“…First, we asked what would be a meaningful effect size for the present research. Pisu et al (2020) reported that non-transformed PRTs group averages of 16 participants in the baseline (congruent) conditions were 890 and 830 ms for pincer and pentapod grips, respectively. In the corresponding test (incongruent) conditions, group averages were 990 and 860 ms (i.e., incongruent distractor-target pair of disks revealed effect sizes of ≈100 and 30 ms).…”

“…Critical for the purpose of the current paper, there is evidence that the effect of the Uznadze illusion might already occur at the level of motor preparation (Pisu et al, 2020). In this work, small, medium, and large disks were used both as distractors and as targets.…”

“…When large targets were grasped after the presentation of smaller distractors, PRTs could not be reliably differentiated from the relevant baseline. Pisu et al (2020) interpreted this pattern as reflecting an asymmetric generalization of precision between the two motor programs. They suggested that the implicit pre-activation of less precise grips (i.e., pentapod) yielded longer PRTs as the precision parameter had to be updated to perform a more demanding grip (i.e., pincer).…”