The influence of action execution on end-state comfort and underlying movement kinematics: An examination of right and left handed participants.

People typically move in an anticipatory manner, planning the intended action in advance to minimize the energy costs associated with producing the action (e.g., Rosenbaum et al., 2009). This is exemplified behaviorally in the end-state comfort effect, which is characterized by the selection of an uncomfortable initial posture to enable a comfortable posture upon completion of the movement (Rosenbaum et al., 1990). The main objective of this study was to further investigate the end-state comfort effect in left- and right-handers (N=20). More specifically, to: (a) understand the influence of mode of action execution; and (b) delineate the role of handedness. The overturned glass task (Fischman, 1997) was used as means of assessment, where participants were asked to demonstrate picking up a glass to pour water in four modes of execution: (1) pantomime without a stimulus; (2) pantomime with image of the glass as a guide; (3) pantomime with glass as a guide; and (4) grasping the glass. End-state comfort was displayed regardless of mode of execution, hand used to complete the task or handedness group. However, kinematic analysis revealed distinct differences, highlighting how movement parameters are altered as a result the mode of action execution.

Can an observational method of assessing hand preference be used to predict language lateralisation?

The current study investigated (a) whether or not the WatHand Cabinet Test (WHCT, Bryden, Roy, & Spence, 2007) could be used as accurately as the Waterloo Handedness Questionnaire (WHQ) to classify individuals into language lateralisation groups based on their hand preference, and (b) the relationship between direction and degree of hand preference and language lateralisation. A total of 142 participants (82 right-handers and 60 left-handers) completed the WHQ and the WHCT, and performed a fused-words dichotic listening test. Findings indicated that the WHCT was robust alternative to the WHQ in providing a measure of hand preference as there was a high correlation between the WHCT and the WHQ, and individuals were divided into similar language lateralisation groups when using either the WHCT or the WHQ as the classifying variable. More specifically, there existed a predictable pattern of language lateralisation into which members of different handedness groups fell. The same pattern exists whether handedness is defined using subjective questionnaires or more objective observational measures of hand preference.

Influences of task complexity, object location, and object type on hand selection in reaching in left and right-handed children and adults.

The effects of task complexity, object location, and object type on reaching behavior were examined. Two hundred ninety-two right-handed and 38 left-handed participants (grouped into five age groups) were asked to pick up or pick up and use objects in different regions of peripersonal space. It was found that individuals used their nonpreferred-hand more often in contralateral space than at the midline position. Using an object resulted in significantly more preferred-hand reaches than picking up an object. Furthermore, task complexity, object location, and object type interacted with each other depending upon age group and hand preference.

An observational method of assessing handedness in children and adults.

The current study was performed to assess the WatHand Cabinet Test (WHCT), a newly developed multidimensional observational test of handedness. Because the test is observational, it is ideal for assessing children, as it does not require a high degree of verbal comprehension on the part of the participants. 548 individuals participated in the present study on a voluntary basis. Individuals of varying ages were examined (including 3 to 5, 6, 7, 8, 9, 10, and 11-year-olds, and 19-to 24-year-olds). Each participant was asked to complete the WHCT, the Annett Pegboard (Annett, 1985), and the Waterloo Handedness Questionnaire (WHQ) (M.P. Bryden, 1977). Overall, the total score on the WHCT was significantly correlated with both the WHQ, r = .795, p < .01, and the Annett Pegboard, r = .542, p < .01. Sub-scores measuring skilled performance, bimanual performance, and internal consistency were also examined, as well as performance on the three tests as a function of age. Overall, findings indicate that that the WHCT is a valid test of hand preference in both children and adults. Its ease of use, quick administration, and built-in quantitative sub-scores offer a robust alternative method for measuring hand preference.

Task demands affect manual asymmetries in pegboard performance.

Previous work by Bryden and Roy (1999) showed a larger performance difference between the hands for placing pegs into holes on the Grooved Pegboard test than for removing pegs from the holes. The authors argued that these data provided evidence of the importance of task demands in manual asymmetries. However the study failed to control for the differing starting positions of the pegs. To clarify this possible confound, the purpose of the current investigation was to determine the influence of starting position on the between-hand performance differences on the Grooved Pegboard Test. To do so, both the start and end positions were manipulated, such that participants moved the pegs from the receptacle to another receptacle or to a set of holes, or participants moved the pegs from a set of holes to a receptacle or another set of holes. A total of 30 right-handed individuals (as classified using the Waterloo Handedness Questionnaire) participated in the experiment, completing five trials with each hand for each of the four conditions. While no significant effects of start position were found, a significant interaction between hand and end position, F(1.29) = 30.85, P<.001, was found for the time to complete the task, where larger differences between the hands, fovouring the right hand, were seen for placing pegs into the holes as opposed to the receptacles. This effect was also found when the data were expressed using a laterality quotient. The results are discussed in terms of the influence of task complexity on manual asymmetries.

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.

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.

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.

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.

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.

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.

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.

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.

Patterns of apraxia associated with the production of intransitive limb gestures following left and right hemisphere stroke.

The model of apraxia proposed by Roy (1996) states that three patterns of apraxia should be observed across pantomime and imitation conditions. In the present analysis the frequency and severity of each pattern of apraxia were examined in a consecutive sample of left-(LHD) and right-hemisphere-damaged (RHD) patients during the production of intransitive limb gestures. The results indicated that a significant proportion of LHD and RHD patients were selectively impaired in formulating the ideational component of intransitive limb gestures.

Transitive gesture production in apraxia: visual and nonvisual sensory contributions.

The production of transitive limb gestures is optimized when the appropriate tool can be physically manipulated. Little research has addressed the independent contributions of visual and nonvisual sources of sensory information to this phenomenon. In this study, 12 control, 37 LHD, and 50 RHD stroke patients performed transitive limb gestures to pantomime (to verbal command with the object visible) and object manipulation. Performance was more accurate in the object manipulation condition, suggesting that haptic and kinesthetic cues are important for transitive gesture production. Various patterns of performance were observed in the stroke groups, indicating that selective damage to the haptic/kinesthetic processing system is possible and common following unilateral stroke.

Memory for kinesthetically defined target location: evidence for manual asymmetries.

Sixteen right-handed male adults performed a pointing task without vision. The participant's arm was moved passively to one of four targets which was subsequently pointed to following a delay of 1, 2, or 10 s. Our previous research on visual memory for target location showed a rapid decay which was comparable for both hands. The present study of memory for kinesthetic target location found decay for the left hand only. These findings suggest two memory stores for target location information, one visual which decays over time but is accessible to both hands and another based on kinesthetic information which is more stable and limb specific.

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.

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.

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.

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.