Biomedical subjects

Matthias Weigelt

Publications and source records attributed to Matthias Weigelt.

6 recordsLinked to original sources

PubMed2006

Returning home: location memory versus posture memory in object manipulation.

Previous studies of object manipulation have suggested that when participants return an object to the place from which they just carried it, they tend to grasp the object for the target-back-to-home trips close to where they just grasped it for the home-to-target trips [Exp Brain Res 157(4):486-495, 2004; Psychon Bull Rev, 2006]. What was unclear from these previous studies was whether participants recalled postures or locations. According to the posture hypothesis, they remembered what body positions they adopted when they last held the object. According to the location hypothesis, they remembered where they held the object and then took hold of it there or nearby again. To distinguish between these possibilities, we had participants mount or dismount a platform after home-to-target moves and before target-back-to-home moves. In the control condition, they did not change their vertical position relative to the shelf containing the home and target platforms (they merely stepped sideways). We found that participants grasped the object at nearly the same place along its length as they had before, even if this meant adopting very different postures than before. This outcome is consistent with the location-recall account and is inconsistent with the posture-recall account. The implications for motor planning are discussed.

Adult↗

PubMed2006

Estimating the quantitative relation between incongruent information and response time.

In Eriksen's flanker paradigm, participants' responses are slower and more error-prone when task-relevant and simultaneously available task-irrelevant cues are incongruent. The influence of task-irrelevant information decreases as its distance from the task-relevant information increases. Here, we manipulated the quantity of task-irrelevant information while keeping the distance constant. We asked whether when the impact on response selection processes was stronger the more incongruent information was available, or whether the impact on response selection depended only on its presence or absence. We conducted an experiment, in which subjects had to discriminate the direction of motion of a central point-light-walker that was flanked by two, four, or eight point-light-walkers at an equal distance from the center. The experiment showed that reaction times increased with the number of incongruent walkers. This effect was modulated by the total number of walkers, showing that the effect of incongruent information saturates when the display is cluttered.

Adult↗

PubMed2006

Target-related coupling in bimanual reaching movements.

While bimanual interference effects can be observed when symbolic cues indicate the parameter values of simultaneous reaching movements, these effects disappear under conditions in which the target locations of two movements are cued directly. The present study investigates the generalizability of these target-location cuing benefits to conditions in which symbolic cues are used to indicate target locations (i.e., the end points of bimanual movements). Participants were asked to move to two of four possible target locations, being located either at the same and different distances (Experiment 1), or in the same and different directions (Experiment 2). Circles and crosses served as symbolic target-location cues and were arranged in a symmetric or non-symmetric fashion over the four target locations. Each trial was preceded by a variable precuing interval. Results revealed faster initiation times for equivalent as compared to non-equivalent target locations (same vs. different cues). Moreover, the time course of prepartion suggests that this effect is in fact due to target-equivalence and not to cue-similarity. Bimanual interference relative to movement parameter values was not observed. These findings suggest that cuing target locations can dominate potential intermanual interference effects during the concurrent programming of different movement parameter values.

Adult↗

PubMed2006

End-state comfort in bimanual object manipulation.

The present experiment investigated the sensitivity for end-state comfort in a bimanual object manipulation task. Participants were required to simultaneously reach for two bars and to place the objects' ends into two targets on the table. The design of the experiment allowed to dissociate the relative roles of initial means (e.g., the selection of grips) and final postures (e.g., the anticipation of end-states). The question of interest was whether affording different grip patterns for the two hands would introduce a bias away from reaching end-state comfort. Results revealed a strong sensitivity for end-state comfort, independent of the required grip patterns. In particular, end-state comfort was preferred even if this meant selecting different initial means (i.e., different grips) for the two hands. Hence, end-state oriented action planning appears to dominate interaction costs that may result from motor-related, intermanual interference. We infer that movement planning is constrained by action goals (e.g., a comfortable end-posture for both hands), but largely unaffected by the type of motor actions necessary to achieve these goals.

Hand↗

PubMed2005

Goal congruency in bimanual object manipulation.

In 3 experiments, the authors investigated the impact of action goals on the production of discrete bimanual responses. Similar to a bartender putting 2 glasses simultaneously on a shelf, participants placed 2 objects into either parallel or opposite orientations by carrying out either mirror-symmetrical or mirror-asymmetrical movements. In Experiment 1, performance was strongly affected by the congruency of the intended object orientations but was essentially unaffected by movement symmetry. Experiment 2 replicated this instrumental goal-congruency effect (and the absence of motor-symmetry effects) when actions were cued in advance. Experiment 3 revealed substantial motor-symmetry effects, provided the movements themselves became the action goal. The authors concluded that performance in bimanual choice reaction tasks is constrained by the creation and maintenance of goal codes rather than by properties inherent in the neuromuscular system that carries out these responses. These goals can relate to either body-intrinsic states or to body-extrinsic states according to the actor's current intentions.

Adult↗

PubMed2003

Attentional focus on suprapostural tasks affects balance learning.

We examined whether the attentional focus induced by a suprapostural task has an influence on the learning of a dynamic balance task. Participants balanced on a stabilometer and were required to hold a tube horizontal with both hands. In Experiment 1, the tube contained a table tennis ball, whereas it was empty in Experiment 2. Participants were instructed to focus on either their hands (internal focus) or the tube (external focus). We measured balance performance as a function of attentional focus on the suprapostural task. Participants practised for 2 days, and on Day 3 they performed a retention test (with tube) and a transfer test (without tube). In both experiments, the external focus groups demonstrated more effective retention and transfer than the internal focus groups (and than the control group in transfer in Experiment 2). In addition, in Experiment 1 the external group was superior in keeping the tube horizontal. This suggests that the performer's attentional focus regarding the suprapostural task affects performance and learning not only of the suprapostural task itself, but also of the postural task.

Attention↗