Biomedical subjects

Petra Jansen-Osmann

Publications and source records attributed to Petra Jansen-Osmann.

11 recordsLinked to original sources

PubMed2007

Maintaining readiness for mental rotation interferes with perceptual processes in children but with response selection in adults.

Previous work revealed that mental rotation is not purely inserted into a same-different discrimination task. Instead, response time (RT) is slowed to upright stimuli in blocks containing rotated stimuli compared to RT to the same upright stimuli in pure upright blocks. This interference effect is a result of maintaining readiness for mental rotation. In two experiments we investigated previous evidence that these costs depend upon distinct sub-processes for children and for adults. In Experiment 1, the maintaining costs turned out to be independent of the visual quality of the stimulus for adults but not so for children. Experiment 2 revealed that the maintaining costs were greatly reduced for adults when they performed mental rotation as a go-no-go task, but not so for children. Taken together, both experiments provide evidence that whereas perceptual processes seem to be important for school-age children to maintain readiness for mental rotation, response selection is relevant for adults.

Adult↗

PubMed2006

Spatial knowledge of children with spina bifida in a virtual large-scale space.

The spatial knowledge of 18 children with spina bifida and 18 healthy control children (matched according to sex, age, and verbal IQ) was investigated in a computer-simulated environment. All children had to learn a route through a virtual floor system containing 18 landmarks. Controlling for cognitive abilities, the results revealed that children with spina bifida showed impaired route knowledge but not an impaired landmark knowledge. Thus the results suggest that children with spina bifida are not impaired in all large-scale abilities similarly. The impairments of the children with spina bifida are more accentuated in more behaviour based measurements, which indicates a relation to the reduced mobility of the children with spina bifida.

Child↗

PubMed2006

Violation of pure insertion during mental rotation is independent of stimulus type, task, and subjects' age.

The experiment validated and extended the finding of Ilan and Miller (1994) [A violation of pure insertion: mental rotation and choice reaction time. Journal of Experimental Psychology: Human Perception and Psychophysics 20, 520-536] that the mental rotation process is not purely inserted into a mirror-normal discrimination task. In contrast to their work we used other experimental stimuli (drawings of animals instead of characters), a different task (same/different comparison) and investigated this effect under a developmental perspective. Adults and children between the age of 8 and 10 took significantly longer to respond to upright drawings of animals in conditions containing rotated stimuli than in conditions containing only upright stimuli, indicating a violation of pure insertion. In general, we found evidence that the violation of pure insertion during a mental rotation task itself can be generalised across stimulus type, task, and subject populations. However, for children this effect was independent of the format of the stimuli, while for adults the effect was larger for mirror-imaged than for identical objects. This suggests that the violation of pure insertion might occur at different processing stages as a function of age.

Adult↗

PubMed2006

Wayfinding behavior and spatial knowledge of adults and children in a virtual environment: The role of landmarks.

This study investigated the effect of different organizations of landmark-location pairings as fine-space information on wayfinding behavior and spatial knowledge on a total of 90 participants: 30 second graders, 30 sixth graders, and 30 adults. All participants had to find their way to a goal in a virtual environment with either randomized or categorical landmarks, or without any landmarks. Thereafter, they had to find the shortest way from the start position to the goal in two consecutive trials (wayfinding performance), and they had to solve a number of spatial knowledge tasks. The results showed that independent of their categorical function, the existence of landmarks influenced the way-finding performance of adults and children in the same way. Whereas the presence of landmarks had no effect on spatial survey knowledge, landmark knowledge itself was influenced by the categorical function of the landmarks presented. Moreover, second graders showed limited achievement compared to adults independent of the existence of landmarks. The main results implicate firstly that children at school age indeed are able to use landmark-location pairings as fine-space information like adults during learning an unknown environmental space, and secondly that a dissociation between wayfinding behavior and spatial knowledge might exist.

Adult↗

PubMed2005

Threading neural feedforward into a mechanical spring: how biology exploits physics in limb control.

A solution is proposed of the hitherto unsolved problem as to how neural feedforward through inverse modelling and negative feedback realised by a mechanical spring can be combined to achieve a highly effective control of limb movement. The revised spring approach that we suggest does not require forward modelling and produces simulated data which are as close as possible to experimental human data. Control models based on peripheral sensing with forward modelling, which are favoured in the current literature, fail to create such data. Our approach suggests that current views on motor control and learning should be revisited.

Adult↗

PubMed2005

What makes a route appear longer? An experimental perspective on features, route segmentation, and distance knowledge.

Five experiments performed in a desktop virtual-reality setting investigated the influence of environmental features--that is, noticeable landmarks along the route--on distance estimation. Landmarks were of two types: Either they simply "filled" the route or they "filled" and also segmented it, thereby inducing a hierarchical structuring of the route. Previous research had left the question open of whether a filling or a segmenting feature leads to an overestimation of a distance along the route. Our experiments showed different results dependent on the kind of space: If an environment was learned from a route perspective, filling and segmenting environmental features led to overestimations of distances, while the segmenting of a route induced by a grouping of similar features did not. If the environment was learned from a map that afforded a survey perspective, route structuring induced through a segmenting feature or by phenomenal grouping led to an overestimation of distances, whereas features that merely filled the route did not.

Adult↗

PubMed2005

Adaptation to separate kinematic and dynamic transformations in children and adults.

The question addressed in the present study is whether children and adults are able to combine and decompose separate kinematic (visual-feedback-shift) and dynamic (velocity-dependent force) transformations in goal-directed arm movements. A total of 64 participants (32 adults and 32 children) performed horizontal forearm movements using a single-joint arm manipulandum. When participants first learned kinematic and dynamic transformations separately, target error decreased in a subsequent combined transformation task. This effect was based on previous learning of the kinematic transformation. When they first learned the combined transformation, target error was smaller in the following kinematic-but not in the dynamic-transformation. No difference was found in adaptation performance between children and adults. The results suggest that there are two separate models for the kinematic and dynamic transformation and that a possible differentiation of kinematic and dynamic features of the motor task might already be present at age 11.

Adaptation, Physiological↗

PubMed2004

Distance cognition in virtual environmental space: further investigations to clarify the route-angularity effect.

Two experiments with 72 participants in total investigated the route-angularity effect. This effect is shown when a greater number of turns along a route increase the estimated length of this route. In this study it was shown that the route-angularity effect is likely to be a memory-based effect depending on task difficulty. The important factor seems to be how heavily memory is loaded during learning. The route-angularity effect even appears in intentional learning, when memory is loaded heavily. Under this learning condition participants know beforehand that they have to estimate distances. All experiments were conducted in a controlled virtual environment, which allows a reliable investigation of distance estimations in environmental space.

Adult↗

PubMed2003

Motor adaptation to different dynamic environments is facilitated by indicative context stimuli.

When humans are exposed to external forces while performing arm movements, they adapt by compensating for these novel forces. The basis of this learning process is thought to be a neural representation that models the relation between all forces acting upon the system and the kinematic effects they produce, called inverse dynamic model (IDM). The present study investigated whether and how the predictability of a given external force affects the selection of an appropriate motor response to compensate for such force. Adult human subjects ( N=32) held a handle that could rotate around the elbow joint and learned to perform goal-directed forearm flexion movements, while an external velocity-dependent negative damping force was applied that assisted forearm movement. Subjects were randomly assigned to two groups. In the associative group, the applied damping force was always associated with a specific initial position. Thus, after initial learning, the force application became predictable. In the non-associative group, where the same movements were performed, the applied force was independent of the initial position, so that no association between force and location could be formed. We found that only the associative group significantly reduced target error when damping was present. That is, the location cue aided these subjects in generating dynamic responses in the appropriate limb. Our results indicate that motor adaptation to different dynamic environments can be facilitated by indicative stimuli.

Adult↗

PubMed2003

Development of force adaptation during childhood.

Humans learn to make reaching movements in novel dynamic environments by acquiring an internal motor model of their limb dynamics. Here, the authors investigated how 4- to 11-year-old children (N = 39) and adults (N = 7) adapted to changes in arm dynamics, and they examined whether those data support the view that the human brain acquires inverse dynamics models (IDM) during development. While external damping forces were applied, the children learned to perform goal-directed forearm flexion movements. After changes in damping, all children showed kinematic aftereffects indicative of a neural controller that still attempted to compensate the no longer existing damping force. With increasing age, the number of trials toward complete adaptation decreased. When damping was present, forearm paths were most perturbed and most variable in the youngest children but were improved in the older children. The findings indicate that the neural representations of limb dynamics are less precise in children and less stable in time than those of adults. Such controller instability might be a primary cause of the high kinematic variability observed in many motor tasks during childhood. Finally, the young children were not able to update those models at the same rate as the older children, who, in turn, adapted more slowly than adults. In conclusion, the ability to adapt to unknown forces is a developmental achievement. The present results are consistent with the view that the acquisition and modification of internal models of the limb dynamics form the basis of that adaptive process.

Adaptation, Physiological↗

PubMed2002

Force adaptation transfers to untrained workspace regions in children: evidence for developing inverse dynamic motor models.

When humans perform goal-directed arm movements under the influence of an external damping force, they learn to adapt to these external dynamics. After removal of the external force field, they reveal kinematic aftereffects that are indicative of a neural controller that still compensates the no longer existing force. Such behavior suggests that the adult human nervous system uses a neural representation of inverse arm dynamics to control upper-extremity motion. Central to the notion of an inverse dynamic model (IDM) is that learning generalizes. Consequently, aftereffects should be observable even in untrained workspace regions. Adults have shown such behavior, but the ontogenetic development of this process remains unclear. This study examines the adaptive behavior of children and investigates whether learning a force field in one hemifield of the right arm workspace has an effect on force adaptation in the other hemifield. Thirty children (aged 6-10 years) and ten adults performed 30 degrees elbow flexion movements under two conditions of external damping (negative and null). We found that learning to compensate an external damping force transferred to the opposite hemifield, which indicates that a model of the limb dynamics rather than an association of visited space and experienced force was acquired. Aftereffects were more pronounced in the younger children and readaptation to a null-force condition was prolonged. This finding is consistent with the view that IDMs in children are imprecise neural representations of the actual arm dynamics. It indicates that the acquisition of IDMs is a developmental achievement and that the human motor system is inherently flexible enough to adapt to any novel force within the limits of the organism's biomechanics.

Adaptation, Physiological↗