12 research outputs found
Catching a Ball at the Right Time and Place: Individual Factors Matter
Intercepting a moving object requires accurate spatio-temporal control. Several studies have investigated how the CNS copes with such a challenging task, focusing on the nature of the information used to extract target motion parameters and on the identification of general control strategies. In the present study we provide evidence that the right time and place of the collision is not univocally specified by the CNS for a given target motion; instead, different but equally successful solutions can be adopted by different subjects when task constraints are loose. We characterized arm kinematics of fourteen subjects and performed a detailed analysis on a subset of six subjects who showed comparable success rates when asked to catch a flying ball in three dimensional space. Balls were projected by an actuated launching apparatus in order to obtain different arrival flight time and height conditions. Inter-individual variability was observed in several kinematic parameters, such as wrist trajectory, wrist velocity profile, timing and spatial distribution of the impact point, upper limb posture, trunk motion, and submovement decomposition. Individual idiosyncratic behaviors were consistent across different ball flight time conditions and across two experimental sessions carried out at one year distance. These results highlight the importance of a systematic characterization of individual factors in the study of interceptive tasks
Sources of variability in interceptive movements
In order to successfully intercept a moving target one must be at the right place at the right time. But simply being there is seldom enough. One usually needs to make contact in a certain manner, for instance to hit the target in a certain direction. How this is best achieved depends on the exact task, but to get an idea of what factors may limit performance we asked people to hit a moving virtual disk through a virtual goal, and analysed the spatial and temporal variability in the way in which they did so. We estimated that for our task the standard deviations in timing and spatial accuracy are about 20 ms and 5 mm. Additional variability arises from individual movements being planned slightly differently and being adjusted during execution. We argue that the way that our subjects moved was precisely tailored to the task demands, and that the movement accuracy is not only limited by the muscles and their activation, but also-and probably even mainly-by the resolution of visual perception
Interaction of visual hemifield and body view in biological motion perception
none6The brain network for the recognition of biological motion includes visual areas
and structures of the mirror-neuron system. The latter respond during action
execution as well as during action recognition. As motor and somatosensory areas
predominantly represent the contralateral side of the body and visual areas
predominantly process stimuli from the contralateral hemifield, we were
interested in interactions between visual hemifield and action recognition. In
the present study, human participants detected the facing direction of profile
views of biological motion stimuli presented in the visual periphery. They
recognized a right-facing body view of human motion better in the right visual
hemifield than in the left; and a left-facing body view better in the left visual
hemifield than in the right. In a subsequent fMRI experiment, performed with a
similar task, two cortical areas in the left and right hemispheres were
significantly correlated with the behavioural facing effect: primary
somatosensory cortex (BA 2) and inferior frontal gyrus (BA 44). These areas were
activated specifically when point-light stimuli presented in the contralateral
visual hemifield displayed the side view of their contralateral body side. Our
results indicate that the hemispheric specialization of one's own body map
extends to the visual representation of the bodies of others.nonede Lussanet MH; Fadiga L; Michels L; Seitz RJ; Kleiser R; Lappe M.de Lussanet, Mh; Fadiga, Luciano; Michels, L; Seitz, Rj; Kleiser, R; Lappe, M