Biomedical subjects

Diala Ammar

Publications and source records attributed to Diala Ammar.

5 recordsLinked to original sources

PubMed2006

Perceived reachability in single- and multiple-degree-of-freedom workspaces.

In comparisons of perceived (imagined) and actual reaches, investigators consistently find a tendency to overestimate. A primary explanation for that phenomenon is that individuals reach as a "whole-body engagement" involving multiple degrees of freedom (m-df). The authors examined right-handers (N = 28) in 1-df and m-df workspaces by having them judge the reachability of targets at midline, right, and left visual fields. Response profiles were similar for total error. Both conditions reflected an overestimation bias, although the bias was significantly greater in the m-df condition. Midline responses differed (greater overestimation) from those of right and left visual fields, which were similar. Although the authors would have predicted better performance in the m-df condition, it seems plausible that if individuals think in terms of m-df, they may feel more confident in that condition and thereby exhibit greater overestimation. Furthermore, the authors speculate that the reduced bias at the side fields may be attributed to a more conservative strategy based in part on perceived reach constraints.

Adult↗

PubMed2005

Hand effects on mentally simulated reaching.

Within the area of simulated (imagined) versus actual movement research, investigators have discovered that mentally simulated movements, like real actions, are controlled primarily by the hemispheres contralateral to the simulated limb. Furthermore, evidence points to a left-brain advantage for accuracy of simulated movements. With this information it could be suggested that, compared to left-handers, most right-handers would have an advantage. To test this hypothesis, strong right- and left-handers were compared on judgments of perceived reachability to visual targets lasting 150 ms in multiple locations of midline, right- and left-visual field (RVF/LVF). In reference to within group responses, we found no hemispheric or hand use advantage for right-handers. Although left-handers revealed no hemispheric advantage, there was a significant hand effect, favoring the non-dominant limb, most notably in LVF. This finding is explained in regard to a possible interference effect for left-handers, not shown for right-handers. Overall, left-handers displayed significantly more errors across hemispace. Therefore, it appears that when comparing hand groups, a left-hemisphere advantage favoring right-handers is plausible.

Adult↗

PubMed2005

Visual cues and perceived reachability.

A rather consistent finding in studies of perceived (imagined) compared to actual movement in a reaching paradigm is the tendency to overestimate at midline. Explanations of such behavior have focused primarily on perceptions of postural constraints and the notion that individuals calibrate reachability in reference to multiple degrees of freedom, also known as the whole-body explanation. The present study examined the role of visual information in the form of binocular and monocular cues in perceived reachability. Right-handed participants judged the reachability of visual targets at midline with both eyes open, dominant eye occluded, and the non-dominant eye covered. Results indicated that participants were relatively accurate with condition responses not being significantly different in regard to total error. Analysis of the direction of error (mean bias) revealed effective accuracy across conditions with only a marginal distinction between monocular and binocular conditions. Therefore, within the task conditions of this experiment, it appears that binocular and monocular cues provide sufficient visual information for effective judgments of perceived reach at midline.

Adult↗

PubMed2005

Motor imagery in reaching: is there a left-hemispheric advantage?

The study of motor imagery affords an attractive approach in the quest to identify the specific aspects of cognitive and neuromotor mechanisms and relationship involved in action processing. Here, the authors investigated the recently reported finding that compared to the left-hemisphere, the right brain is at a significant disadvantage for mentally simulating reaching movements. The authors investigated this observation with strong right-handers that were asked to estimate the imagined reachability of visual targets (presented at 150 ms) at multiple points at midline, right- and left visual field; responses were compared to actual maximum reaching distance. Results indicated that individuals are relatively accurate at imagined reachability, with no significant distinction between visual field responses. Therefore, these data provide no evidence to support the claim that the right hemisphere is significantly inferior to the left hemisphere in estimations of motor imagery for reaching. The authors do acknowledge differences in the experimental task and subject characteristics compared to earlier work using split-brain and stroke patients.

Adult↗

PubMed2004

Perceived reachability in hemispace.

A common observation in studies of perceived (imagined) compared to actual movement in a reaching paradigm is the tendency to overestimate. Of the studies noted, reaching tasks have been presented in the general midline range. In the present study, strong right-handers were asked to judge the reachability of visual targets projected onto a table surface at midline, right- (RVF), and left-visual fields (LVF). Midline results support those of previous studies, showing an overestimation bias. In contrast, participants revealed the tendency to underestimate their reachability in RVF and LVF. These findings are discussed from the perspective of actor 'confidence' (a cognitive state) possibly associated with visual information, perceived ability, and perceived task demands.

Adult↗