Search results for "Movement"
showing 10 items of 2021 documents
Motor planning of arm movements is direction-dependent in the gravity field.
2007
International audience; In the present study we analyzed kinematic and dynamic features of arm movements in order to better elucidate how the motor system integrates environmental constraints (gravity) into motor planning and control processes. To reach this aim, we experimentally manipulated the mechanical effects of gravity on the arm while maintaining arm inertia constant (i.e. the distribution of the mass around the shoulder joint). Six subjects performed single-joint arm movements (rotation around the shoulder joint) in both sagittal (upward, U, versus downward, D) and horizontal (left, L, versus right, R) planes, at different amplitudes and from different initial positions. Under thes…
Pointing to double-step visual stimuli from a standing position: motor corrections when the speed-accuracy trade-off is unexpectedly modified in-flig…
2011
The time required to complete a fast and accurate movement is a function of its amplitude and the target size. This phenomenon refers to the well known speed-accuracy trade-off. Some interpretations have suggested that the speed-accuracy trade-off is already integrated into the movement planning phase. More specifically, pointing movements may be planned to minimize the variance of the final hand position. However, goal-directed movements can be altered at any time, if for instance, the target location is changed during execution. Thus, one possible limitation of these interpretations may be that they underestimate feedback processes. To further investigate this hypothesis we designed an ex…
Effects of Emotional Context on Memory for Details: The Role of Attention
2013
It was repeatedly demonstrated that a negative emotional context enhances memory for central details while impairing memory for peripheral information. This trade-off effect is assumed to result from attentional processes: a negative context seems to narrow attention to central information at the expense of more peripheral details, thus causing the differential effects in memory. However, this explanation has rarely been tested and previous findings were partly inconclusive. For the present experiment 13 negative and 13 neutral naturalistic, thematically driven picture stories were constructed to test the trade-off effect in an ecologically more valid setting as compared to previous studies…
Did you see that? Dissociating advanced visual information and ball flight constrains perception and action processes during one-handed catching
2013
The integration of separate, yet complimentary, cortical pathways appears to play a role in visual perception and action when intercepting objects. The ventral system is responsible for object recognition and identification, while the dorsal system facilitates continuous regulation of action. This dual-system model implies that empirically manipulating different visual information sources during performance of an interceptive action might lead to the emergence of distinct gaze and movement pattern profiles. To test this idea, we recorded hand kinematics and eye movements of participants as they attempted to catch balls projected from a novel apparatus that synchronised or de-synchronised ac…
Who is looking at me? The cone of gaze widens in social phobia
2011
Gaze direction is an important cue that regulates social interactions and facilitates joint attention. Although humans are very accurate in determining gaze directions in general, they have a surprisingly liberal criterion for the presence of mutual gaze. Using an established psychophysical task that required observers to adjust the eyes of a virtual head to the margins of the area of mutual gaze, we examined whether the resulting cone of gaze is altered in people with social phobia. It turned out that during presence of a second virtual person, the gaze cone's width was specifically enlarged in patients with social phobia as compared to healthy controls. The size of this effect was correla…
Prism adaptation by mental practice
2012
International audience; The prediction of our actions and their interaction with the external environment is critical for sensorimotor adaptation. For instance, during prism exposure, which deviates laterally our visual field, we progressively correct movement errors by combining sensory feedback with forward model sensory predictions. However, very often we project our actions to the external environment without physically interacting with it (e.g., mental actions). An intriguing question is whether adaptation will occur if we imagine, instead of executing, an arm movement while wearing prisms. Here, we investigated prism adaptation during mental actions. In the first experiment, participa…
Pointing to double-step visual stimuli from a standing position: very short latency (express) corrections are observed in upper and lower limbs and m…
2010
How fast can we correct a planned movement following an unexpected target jump? Subjects, starting in an upright standing position, were required to point to a target that randomly and unexpectedly jumps forward to a constant spatial location. Rapid motor corrections in the upper and lower limbs, with latency responses of less than 100 ms, were revealed by contrasting electromyographic activities in perturbed and unperturbed trials. The earliest responses were observed primarily in the anterior section of the deltoidus anterior (shoulder) and the tibialis anterior (leg) muscles. Our findings indicate that visual on-going movement corrections may be accomplished via fast loops at the level o…
Modulation of premotor mirror neuron activity during observation of unpredictable grasping movements.
2004
Using transcranial magnetic stimulation, we explored the properties of premotor mirror neurons during the passive observation of a reaching-grasping movement in human subjects. Two different experiments were run using video-clips as visual stimuli. Video-clips showed a normally performed (control stimulus) or an anomalous reaching-grasping movement executed by delaying the time of the appearance of the maximal finger aperture (experiment 1), or substituting it with an unpredictable closure (experiment 2). Motor evoked potentials were recorded at different time-points during the observation of the video-clips. Profiles of cortical excitability were drawn and compared with the kinematic profi…
Release of premotor activity after repetitive transcranial magnetic stimulation of prefrontal cortex
2008
In the present study we aimed to explore by means of repetitive transcranial magnetic stimulation (rTMS) the reciprocal influences between prefrontal cortex (PFC) and premotor cortex (PMC). Subjects were asked to observe on a computer monitor different pictures representing manipulations of different kind of tools. They had to produce a movement (go condition) or to keep the resting position (no-go condition) at the appearance of different cue signals represented by different colors shown alternatively on the hands manipulating the tools or on the picture background. Motor evoked potentials (MEPs) were collected at the offset of the visual stimuli before and after a 10 minute, 1 Hz rTMS tra…
COMT genotype predicts BOLD signal and noise characteristics in prefrontal circuits.
2006
Abstract Objective: Prefrontal dopamine (DA) is catabolized by the COMT (catechol- O -methyltransferase) enzyme. Literature suggests that the Val/Met single nucleotide polymorphism (SNP) in the COMT gene predicts executive cognition in humans with Val carriers showing poorer performance due to less available synaptic DA. Recent fMRI studies are thought to agree with these studies having demonstrated prefrontal hyperactivation during n -back and attention-requiring tasks. This was interpreted as “less efficient” processing due to impaired signal-to-noise ratio (SNR) of neuronal activity. However, electrophysiological studies of neuronal SNR in primates and humans imply that prefrontal cortex…