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Biomedical subjects

E A Roy

Publications and source records attributed to E A Roy.

At least 19 recordsLinked to original sources
PubMed2006

Preferential reaching across regions of hemispace in adults and children.

The purpose of the current study was to examine hand selection during reaching in children utilizing a developmental version of the preferential reaching paradigm (Bryden, Pryde, & Roy, 2000). A cross-sectional sample of eighty right-handed participants (ranging in age from 3 to 20 years) were asked to reach to objects located in different regions of hemispace. Each participant was asked to carry out two different actions, varying in degree of complexity, on the objects while the experimenter observed, which hand was used to perform each of the tasks. A repeated-measures ANOVA revealed that reaching towards the midline and ipsilateral positions in hemispace resulted in significantly more preferred hand reaches than reaching towards contralateral hemispace, regardless of age and task. With respect to age group effects, it was found that the 6 and 7 year olds and the 9 and 10 year olds relied heavily on their preferred hand to perform the task, indicating that hand selection in these children was driven primarily by motor dominance. In comparison, the youngest children and adults used their nonpreferred hand more frequently in contralateral space, indicating that object proximity cues or a hemispheric bias was driving hand selection. The implications of these findings for understanding hand preference and skill were discussed in terms of motor dominance versus spatial reasoning theory of hand selection in unimanual reaching.

Adolescent↗
PubMed2005

Unimanual performance across the age span.

The purpose of the current investigation was to examine the age-related changes in the performance of the two hands on the Annett pegboard (Annett, 1970). The current study was part of a large-scale study investigating the development of unimanual and bimanual performance. Three hundred and two right-handed individuals participated in the present study, comprising five different age groups (3-5 year olds, 6 and 7 year olds, 8 and 9 year olds, 10-12 year olds, and 19-24 year olds). All participants completed the Waterloo Handedness Questionnaire and the standard Annett pegboard. Analyses revealed significant overall performance differences between the hands, as expected, where the right hand was significantly faster than the left hand. Additionally, significant performance differences between the hands were noted as a function of age. More specifically, the adults showed a much smaller performance difference between the hands than the other age groups. The results are discussed in light of current theories of the development of hand preference and manual asymmetry.

Adult↗
PubMed2005

A new method of administering the Grooved Pegboard Test: performance as a function of handedness and sex.

The purpose of the present study was twofold: first to examine the influences of sex and handedness on manual performance on the Grooved Pegboard Test; and secondly to provide normative data for two versions (Place and Remove tasks) of the Grooved Pegboard Test, as previous work (Bryden & Roy, 1999) had suggested that the Remove task of the Grooved pegboard may provide a purer measure of motor speed of the two hands than the standard administration of the Grooved Pegboard Test. One hundred and fifty-three (47 males and 106 females) participants completed the Grooved Pegboard Test. Individuals performed the standard version of the Grooved Pegboard Test (Place task) and a novel version of the test (Remove task). In the standard version, participants were timed on their speed for placing the pegs, while in the novel version they were timed on their speed for removing the pegs. Results confirmed previously noted hand and sex differences in the Place task of the Grooved Pegboard Test, as well as the lack of effect of handedness on performance (Bornstein, 1995; Ruff & Parker, 1993). Significant performance differences between the hands were also noted for the Remove task. Findings also indicated that the Remove task was sensitive to sex and handedness effects.

Adolescent↗
PubMed2005

An evaluation of sensorimotor integration during locomotion toward a target in Parkinson's disease.

Recent research suggests that basal ganglia dysfunction may result in problems integrating concurrent vision and proprioception during movement. We evaluated dopaminergic system involvement in this sensorimotor process during locomotion within a large sample of Parkinson's disease (PD) patients while "On" and "Off" their dopaminergic medications (n=25), in conditions that selectively manipulated the availability of proprioception, vision or both. The present experiment focused on two main objectives: i) to examine the relative influence of visual and proprioceptive inputs on locomotion and target accuracy in patients with PD; and ii) to examine the influence of dopamine replacement therapy on sensorimotor integration while moving toward the target. All participants walked at a self-selected pace on a GAITRite carpet in two baseline conditions (light and dark), as well as four experimental darkness conditions: a) to a remembered target (i.e. proprioception only), b) to a remembered target with light on chest for body position awareness (proprioception plus), c) with vision of a lit target, also with light on chest (vision and proprioception), d) pushed in wheelchair to remembered target (no proprioception or vision). Final position was measured by 2-D radial error, and revealed a group by condition interaction, suggesting that PD patients "Off" their medications move to targets with less accuracy, but approach the accuracy of healthy participants when in the "On" state. Both PD and healthy improved their accuracy with availability of concurrent vision and proprioception (condition c). Interestingly, our results demonstrate that PD "Off" performed the task with greater difficulty than when "On" medication, but only when proprioception was the sole source of feedback. Since PD, whether medicated or unmedicated were even more affected when proprioception was removed (wheelchair), a memory-related explanation can be ruled out. Our results suggest that the basal ganglia are not specifically involved in visuoproprioceptive integration; however, assimilation of proprioceptive feedback to guide an ongoing movement may be a critical function of the basal ganglia.

Adult↗
PubMed2004

The effects of concurrent experimental infections of sheep with Trichostrongylus colubriformis and T. vitrinus on nematode distributions, numbers and on pathological changes.

Simultaneous infections of Trichostrongylus colubriformis and T. vitrinus in the small intestine of the sheep were examined by comparing the numbers of worms which established and their distribution within the intestine in both monospecific infections and mixed infections. The results differed depending upon the species and number of parasites. The establishment of T. colubriformis was reduced and the distribution of the nematode population was displaced posteriorly within the intestine when 30,000 larvae of both species were administered, compared with pure infections of T. colubriformis. The reduced establishment was less marked with infections of 15,000 larvae of both species and there was only a slight posterior displacement of T. colubriformis. Neither effect was evident with infections of 7,500 larvae of both species. The rate of establishment and distribution of T. vitrinus were unaffected by the presence of T. colubriformis at all three rates of infection. Atrophy of villi and hypertrophy of crypts occurred at the main site of infection in the anterior duodenum. The severity of villus atrophy was related to the number of infective larvae administered and/or the worm burden. In the ileum, beyond the main site of infection, hypertrophy of villi was only found in sheep receiving the greatest number of infective larvae.

Analysis of Variance↗
PubMed2003

Influence of terminal action requirements on action-centered distractor effects.

Tipper (1985; Q J Exp Psychol A 37:571-590) has suggested that competing responses programmed to distracting stimuli are inhibited based on their relationship to the action being performed. The present paper reports two experiments designed to examine the influence of the terminal action of a task on the allocation of visual attention. Taken together the results suggest that when engaging targets in an environment, which includes distracting stimuli, competing responses are likely to be programmed in parallel and that the relationship between competing responses can include both spatial position and action characteristics.

Adult↗
PubMed2002

Vibrotaction and texture perception.

Several recent studies support Katz's hypothesis that vibrotaction plays a role in the perception of tactile textures with elements too small and closely spaced to be processed spatially. For example, eliminating vibration by preventing movement of a stimulus surface across the skin compromises psychophysical scaling and discrimination of fine, but not coarse, textures. Fine-texture discrimination is also impaired when vibrotactile channels are desensitized by adaptation. A role for vibrotaction in texture perception is plausible, given the keenness of this submodality: the sensory qualities produced by a sinusoidal vibration uniquely specify its frequency and amplitude, and subjects can distinguish some complex vibrations that differ in waveform but have the same spectral components. Finally, imposed vibration can modify the perceived texture of a haptically-examined surface. Taken together, these lines of evidence support the view that vibrotaction is both necessary and sufficient for the perception of fine tactile textures.

Humans↗
PubMed2001

Delayed grasping of a Müller-Lyer figure.

Grasping movements are more sensitive to the Müller-Lyer (ML) illusion when the response is made after a brief period of visual occlusion. It is unclear whether this effect is due to (1) the elimination of on-line visual feedback, or (2) reliance on a stored perceptual representation of the target for movement planning. Here participants grasped objects from within two forms of a ML figure in four visual conditions (full vision, open-loop, brief delay, and 2-s delay) and estimated object size in the full-vision condition. Peak grasping aperture was influenced by the ML figure in the full-vision condition, although to a much smaller extent than was true for manual size estimation. The effect of the ML figure on peak grasping aperture was substantially increased in the open-loop and delay conditions, which did not differ from one another. These findings highlight the importance of on-line visual feedback for the resistance of grasping to the ML illusion and also call to attention the relevance of task factors such as target previewing, the visuomotor relevance of illusion-inducing elements, and participant strategies.

Adult↗
PubMed2001

The accuracy of reaching movements in brief delay conditions.

We tested the hypothesis that a highly accurate target representation is available to the visuomotor system in brief (< 2 s) delay conditions. Participants reached to single midsagittal targets (20, 25, 30, 35, 40 cm amplitude) in full vision, open-loop and delay conditions (500, 1,000, 1,500 or 2,000 ms). Radial endpoint error was significantly greater for open-loop than full vision reaches, and was greater still for all delay conditions, which did not differ from one another. Radial error was greater for farther targets, although this tended to hold only for delayed reaches. These data suggest that the visuomotor system switches from on-line visual information to a degraded, stored representation very soon (< 500 ms) if not immediately after target occlusion.

Adult↗
PubMed2001

Intransitive limb gestures and apraxia following unilateral stroke.

Apraxia is the loss of the ability to perform learned, skilled movements correctly, and is frequently attributed to left hemisphere damage (Heilman & Rothi, 1985). Recent work (Dumont, Ska, & Schiavetto, 1999) has shown a dissociation between transitive (tool based; e.g., hammering a nail) and intransitive (expressive/ communicative; e.g., waving goodbye) actions; however, few group studies have specifically addressed apraxia for intransitive gestures. The present investigation examined the frequency and severity of praxis errors related to the production of intransitive gestures in left (LHD) or right hemisphere stroke (RHD) patients in the context of Roy's (1996) model of limb praxis. A total of 119 consecutive stroke patients (LHD = 57, RHD = 62) and 20 healthy age-matched controls performed eight intransitive gestures to pantomime and imitation. Performance was quantified via a multi-dimensional error notation system, providing detail about specific elements of performance (e.g., location), and a composite score reflecting overall gestural accuracy. Analyses of pantomime and imitation performance revealed an equal percentage of apraxic patients in each stroke group, and the severity of apraxia in these groups was also equivalent. Further, analyses of the patterns of apraxia specified by Roy (1996) revealed that patients in each stroke group demonstrated selective impairments in pantomime (LHD = 38%, RHD = 42%), or imitation (LHD = 9%, RHD = 5%) conditions, whereas others demonstrated concurrent impairments (LHD = 30%, RHD = 22%) indicating that stroke to either hemisphere can selectively impair each stage in the production of an intransitive action.

Aged↗
PubMed2000

A performance measure of the degree of hand preference.

The present paper describes a performance method for determining hand preference. The task requires participants to reach into different regions of hemispace to perform various actions (point, pick up, toss, sweep, and position) with a dowel located at each position. In accordance with the participants' hand preference as measured by the Waterloo Handedness Questionnaire, the preferred hand was used more frequently on the various performance tasks. The distribution of hand use in working space indicates that preferred hand use was almost exclusive for actions carried out in ipsilateral hemispace, while it is used only moderately for actions in contralateral hemispace, revealing that this hand is used throughout a wider range of extrapersonal space than the nonpreferred hand. These trends were observed across all of the performance tasks, suggesting that task complexity did not affect the frequency of preferred hand use either overall or, more specifically, in right hemispace, as was predicted. This finding is inconsistent with empirical work on questionnaires indicating that verbal reports of preferred hand use increase for more complex tasks (e.g., Steenhuis & Bryden, 1988). As well, performance on the preferential reaching task correlated significantly with hand preference as measured on the Waterloo Handedness Questionnaire (Bryden, 1977), unlike the other performance measure examined, indicating that the preferential reaching task is sensitive to differences in the degree of hand preference.

Adult↗
PubMed2000

Task demands and limb apraxia in stroke.

The present study was designed to examine the frequency and severity of apraxia in patients with left- or right-hemisphere stroke in both pantomime and imitation conditions and to compare the frequency of apraxia in each stroke group across the three patterns of apraxia described in Roy's model (Roy, 1996). Ninety-nine stroke patients and 15 age-matched healthy adults performed eight transitive gestures to pantomime and to imitation. Gestural performance was quantified as accuracy on five performance dimensions; a composite score, an arithmetic combination of the five performance dimensions, was used as an index of the overall accuracy. Analyses revealed a comparable proportion of patients in each stroke group were classified as apraxic in the imitation condition, but a higher proportion of left stroke patients were apraxic in the pantomime condition. The severity of apraxia in each stroke group and the performance dimensions affected were, however, comparable. Analyses of the patterns of apraxia (pantomime alone, imitation alone or apraxia in both conditions) revealed a higher frequency of apraxia in both stroke groups for the pattern reflecting apraxia in both conditions, indicating that a disruption at the movement execution stage of gesture performance was most common.

Aged↗
PubMed2000

The effect of a pictorial illusion on closed-loop and open-loop prehension.

It has been proposed that movements to visible and remembered targets are sensitive to qualitatively different types of visual information. When the target is continuously visible, prehensile movements are thought to reflect veridical object size, whereas memory-dependent prehension is sensitive to the perceived size of the object. This hypothesis was explored by assessing the influence of illusory target width on prehension kinematics in three visual conditions: closed-loop (CL; full vision during the response), open-loop brief-delay (OL; visual occlusion coincident with the movement initiation cue) and open-loop 3-s delay (OL3; visual occlusion 3 s prior to movement initiation). To modulate illusory target width, objects were placed on backgrounds consisting of three forms of the Müller-Lyer (ML) figure. Peak grip aperture was sensitive to the ML figure in the OL and OL3, but not CL conditions, suggesting that perceptual information is used to modulate this grasping parameter when the movement is programmed and executed on the basis of visual memory. Peak-aperture velocity was affected by the ML illusion in all three visual conditions, suggesting that perceived object size might be important for modulating this aspect of prehension, independent of memory requirements. The different sensitivity of grip aperture and aperture velocity to illusory target width in the CL condition suggests that grasp preshaping might reflect multiple visuomotor processes. The results of this study are consistent with the tenets of the two-stream model of visual processing.

Adult↗
PubMed2000

The effect of illusory size on force production when grasping objects.

Milner and Goodale (1995) have proposed that visuomotor and perceptual processes are mediated by discrete visual systems that reflect the functional independence of action and perception. The visuomotor system is proposed to be insensitive to pictorial illusions of object size, whereas the perceptual system is reliably "tricked" by such figures. Brenner and Smeets (1996) and Jackson and Shaw (2000) demonstrated that grasp preshaping, but not grasping force, is immune to the Ponzo visual illusion, suggesting that not all visuomotor processes operate independently of the perceptual system. The present study investigated the effect of illusory object size on prehension kinematics and grasping dynamics (i.e., grip force and load force) as well as perceptual judgements of object size. Unlike previous investigations, object mass was held constant independent of changes in size. The Ponzo figure reliably affected perceptual estimates of object size, but this effect was restricted to one form of the illusion. Some aspects of the prehension movement were sensitive to veridical but not illusory object size (peak grip aperture, peak grip force, peak vertical wrist acceleration), whereas other movement parameters demonstrated illusory size effects (movement time, peak wrist velocity). Still other movement parameters were not sensitive to veridical or illusory object size (peak load force). Together the data suggest that certain prehension components are immune to pictorial illusions of object size, whereas others are not. Complex interactions between the perceptual and visuomotor systems appear to underlie the anticipatory scaling of grasping forces in prehension.

Acceleration↗
PubMed2000

Pantomimed actions may be controlled by the ventral visual stream.

Several studies have demonstrated that while perceptual judgements of object size can be biased by visual illusions, actions remain more closely scaled to true object properties. This dissociation is often cited in support of a two-stream model of visual processing, in which visual perception is thought to be mediated by a ventral stream, while goal-directed actions are controlled by a dorsal stream. Evidence suggests that pantomimed actions (i.e., actions directed toward remembered targets) are controlled differently to natural actions; indeed, it has been proposed that pantomimed actions are mediated by the ventral rather than the dorsal stream. To test this hypothesis, we examined the effect of a visual size illusion (a variation of the Müller-Lyer figure) on manual aperture formation during natural and pantomimed prehension (i.e., action) and aperture scaling (i.e., perception). As found in earlier studies, mean peak aperture (MPA) was significantly affected by the illusion in the perception task but not the natural action task. In the pantomime condition, action and perception were equally affected by the illusion as reflected by MPA. These results provide support for the hypothesis that pantomimed actions are mediated by the ventral visual processing stream, while natural actions depend on the dorsal stream.

Adult↗
PubMed1999

Spatial task demands affect the extent of manual asymmetries.

The degree of hand preference and the magnitude of hand differences in performance are thought to relate to skill level. The purpose of the experiments discussed here was to examine the effect of skill as reflected in the spatial precision demands of a movement, on the extent of manual asymmetries. Experiment 1 utilised the Annett pegboard, and manipulated spatial precision by varying peg diameter. The second experiment utilised the Grooved pegboard, and manipulated spatial precision by altering the size of the target hole. Analyses revealed that movement time increased as a function of the increased spatial precision demands. Although the preferred hand was always faster, the magnitude of this advantage was only affected in Experiment 2, in which the manipulation of spatial precision was maximal. The implications of these findings for the skill interpretation of handedness are discussed.

Journal Article↗
PubMed1998

Analyses of deficits in gestural pantomime.

The frequency and characteristics of apraxia in 63 stroke patients with left- or right-hemisphere damage were examined. Analyses focussing on five dimensions of gestural performance revealed an overall frequency of apraxia of 54% in patients with LHD and 30% in patients with RHD. Although both groups were impaired on the orientation and hand posture dimensions of performance, the patients with RHD exhibited significantly poorer performance on the location dimension and the patients with LHD on the action dimension. Analyses of intrahemispheric lesion localization implicated damage to subcortical areas involving periventricular white matter tracts at the temporoparietal junction with apraxia.

Aged↗