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

The effect of the Uznadze illusion is temporally dynamic in closed-loop but temporally constant in open-loop grasping

Although it is known that the availability of visual feedback modulates grasping kinematics, it is unclear whether this extends to both the early and late stages of the movement. We tackled this issue by exposing participants to the Uznadze illusion (a medium stimulus appears larger or smaller after exposure to smaller or larger inducers). After seeing smaller or larger discs, participants grasped a medium disc with (closed-loop [CL]) or without (open-loop [OL]) visual feedback. Our main aim was to assess whether the time course of the illusion from the movement onset up to the grasp differed between OL and CL. Moreover, we compared OL and CL illusory effects on maximum grip aperture (MGA) and tested whether preparation time, movement time, and time to MGA predicted illusion magnitude. Results revealed that CL illusory effects decreased over movement time, whereas OL ones remained constant. At the time of MGA, OL, and CL effects were, however, of similar size. Although OL grasps were longer to prepare and showed earlier and larger MGAs, such differences had little impact on modulating the illusion. These results suggest that the early stage of grasping is sensitive to the Uznadze illusion both under CL and OL conditions, whereas the late phase is sensitive to it only under OL conditions. We discuss these findings within the framework of theoretical models on the functional properties of the dorsal stream for visually guided actions.

Emergent and planned interpersonal synchronization are both sensitive to 'tempo aftereffect contagion'

Interpersonal synchronization is fundamental for motor coordination during social interactions. Discerning emergent (entrainment) from planned synchronization represents a non-trivial issue in visually bonded individuals acting together, as well as assessing whether inter-individual differences, e.g., in autistic traits, modulate both types of synchronization. In a visuomotor finger-tapping task, two participants replicated a target tempo either synchronizing ('joint' condition) or not ('non-interactive' condition, 'non-int') with each other. One participant was exposed ('induced') to tempo aftereffect (a medium tempo seems faster or slower after exposure to slower or faster inducing tempi), but not the other participant ('not induced'); thus they had different timing perceptions of the same target. We assessed to what degree emergent and/or planned synchronization affected dyads by analyzing inter-tap-intervals, synchronization indexes, and cross-correlation coefficients. Results revealed a 'tempo aftereffect contagion': inter-tap-intervals of both induced and not-induced participants showed aftereffect in both the joint and non-int conditions. Moreover, aftereffects did not correlate across conditions suggesting they might be due to (at least in part) different processes, but the propensity for tempo aftereffect contagion correlated with individuals' autistic traits only in the non-int condition. Finally, participants co-adjusted their tapping more in the joint condition than in the non-int one, as confirmed by higher synchronization indexes and the mutual adaptation pattern of cross-correlation coefficients. Altogether, these results show the subtle interplay between emergent and planned interpersonal synchronization mechanisms that act on a millisecond timescale independently from synching or not with the partner.

Information transmission in action video gaming experts: Inferences from the lateralized readiness potential

Research showed that action real-time strategy gaming (ARSG) experience is related to cognitive and neural plasticity, including visual selective attention and working memory, executive control, and information processing. This study explored the relationship between ARSG experience and information transmission in the auditory channel. Using an auditory, two-choice, go/no-go task and lateralized readiness potential (LRP) as the index to partial information transmission, this study examined information transmission patterns in ARSG experts and amateurs. Results showed that experts had a higher accuracy rate than amateurs. More importantly, experts had a smaller stimulus-locked LRP component (250 – 450 ms) than amateurs on no-go trials, while the response-locked LRP component (0 – 300 ms) on go trials did not differ between groups. Thus, whereas amateurs used an asynchronous information transmission pattern, experts used a reduced asynchronous information transmission pattern or a synchronous pattern where most of processing occurred prior to response execution – an information transmission pattern that supports rapid, error-free performance. Thus, experts and amateurs may use different information transmission patterns in auditory processing. In addition, the information transmission pattern used by experts is typically observed only after long-term auditory training according to past research. This study supports the relationship between ARSG experience and the development of information processing patterns.