Manual asymmetries in the kinematics of a reach-to-grasp action

Healthy adults favor stable left/right hand choices over performance at an unconstrained reach-to-grasp task

Reach-to-grasp actions are fundamental to the daily activities of human life, but few methods exist to assess individuals' reaching and grasping actions in unconstrained environments. The Block Building Task (BBT) provides an opportunity to directly observe and quantify these actions, including left/right hand choices. Here we sought to investigate the motor and non-motor causes of left/right hand choices, and optimize the design of the BBT, by manipulating motor and non-motor difficulty in the BBT's unconstrained reach-to-grasp task. We hypothesized that greater motor and non-motor (e.g. cognitive/perceptual) difficulty would drive increased usage of the dominant hand. To test this hypothesis, we modulated block size (large vs. small) to influence motor difficulty, and model complexity (10 vs. 5 blocks per model) to influence non-motor difficulty, in healthy adults (n = 57). Our data revealed that increased motor and non-motor difficulty led to lower task performance (slower task speed), but participants only increased use of their dominant hand only under the most difficult combination of conditions: in other words, participants allowed their performance to degrade before changing hand choices, even though participants were instructed only to optimize performance. These results demonstrate that hand choices during reach-to grasp actions are more stable than motor performance in healthy right-handed adults, but tasks with multifaceted difficulties can drive individuals to rely more on their dominant hand.

Revisiting the effect of visual illusions on grasping in left and right handers

Visual illusions have provided compelling evidence for a dissociation between perception and action. For example, when two different-sized objects are placed on opposite ends of the Ponzo illusion, people erroneously perceive the physically smaller object to be bigger than the physically larger one, but when they pick up the objects, their grip aperture reflects the real difference in size between the objects. This and similar findings have been demonstrated almost entirely for the right hand in right handers. The scarce research that has examined right and left-handed subjects in this context, has typically used only small samples. Here, we extended this research with a larger sample size (more than 50 in each group) in a version of the Ponzo illusion that allowed us to disentangle the effects of real and illusory size on action and perception in much more powerful way. We also collected a wide range of kinematic measures to assess possible differences in visuomotor control in left and right handers. The results showed that the dissociation between perception and action persisted for both hands in right handers, but only for the right hand in left handers. The left hand of left handers was sensitive to the illusion. Left handers also showed more variable and slower movements, as well as larger safety margins in both hands. These findings suggest that grasping in left handers may require more cognitive supervision, which could lead to greater sensitivity to visual context , particularly with their dominant left hand.

Upper extremity asymmetry due to nerve injuries or central neurologic conditions: a scoping review

BACKGROUND

Peripheral nerve injuries and central neurologic conditions can result in extensive disabilities. In cases with unilateral impairment, assessing the asymmetry between the upper extremity has been used to assess outcomes of treatment and severity of injury. A wide variety of validated and novel tests and sensors have been utilized to determine the upper extremity asymmetry. The purpose of this article is to review the literature and define the current state of the art for describing upper extremity asymmetry in patients with peripheral nerve injuries or central neurologic conditions.

METHOD

An electronic literature search of PubMed, Scopus, Web of Science, OVID was performed for publications between 2000 to 2022. Eligibility criteria were subjects with neurological conditions/injuries who were analyzed for dissimilarities in use between the upper extremities. Data related to study population, target condition/injury, types of tests performed, sensors used, real-world data collection, outcome measures of interest, and results of the study were extracted. Sackett's Level of Evidence was used to judge the quality of the articles.

RESULTS

Of the 7281 unique articles, 112 articles met the inclusion criteria for the review. Eight target conditions/injuries were identified (Brachial Plexus Injury, Cerebral Palsy, Multiple Sclerosis, Parkinson's Disease, Peripheral Nerve Injury, Spinal Cord Injury, Schizophrenia, and stroke). The tests performed were classified into thirteen categories based on the nature of the test and data collected. The general results related to upper extremity asymmetry were listed for all the reviewed articles. Stroke was the most studied condition, followed by cerebral palsy, with kinematics and strength measurement tests being the most frequently used tests. Studies with a level of evidence level II and III increased between 2000 and 2021. The use of real-world evidence-based data, and objective data collection tests also increased in the same period.

CONCLUSION

Adequately powered randomized controlled trials should be used to study upper extremity asymmetry. Neurological conditions other than stroke should be studied further. Upper extremity asymmetry should be measured using objective outcome measures like motion tracking and activity monitoring in the patient's daily living environment.

Task-Related Differences in End-Point Kinematics in School-Age Children with Typical Development

Understanding whether and how children with typical development adapt their reaches for different functional tasks could inform a more targeted design of rehabilitation interventions to improve upper extremity function in children with motor disabilities. This prospective study compares timing and coordination of a reach-to-drink, reach-to-eat, and a bilateral reaching task in typically developing school-aged children. Average speed, straightness, and smoothness of hand movements were measured in a convenience sample of 71 children, mean age 8.77 ± 0.48 years. Linear mixed models for repeated measures compared the variables by task, phases of the reach, task x phase interactions, and dominant versus non-dominant hands. There were significant main effects for task and phase, significant task x phase interactions (p < 0.05), and a significant difference between the dominant and non-dominant hand for straightness. Hand movements were fastest and smoothest for the reach-to-eat task, and least straight for the bilateral reaching task. Hand movements were also straighter in the object transport phases than the prehension and withdrawal phases. These results indicate that children with typical development change their timing and coordination of reach based on the task they are performing. These results can inform the design of rehabilitation interventions targeting arm and hand function.

On the Neurocircuitry of Grasping: The influence of action intent on kinematic asymmetries in reach-to-grasp actions

Evidence from electrophysiology suggests that nonhuman primates produce reach-to-grasp movements based on their functional end goal rather than on the biomechanical requirements of the movement. However, the invasiveness of direct-electrical stimulation and single-neuron recording largely precludes analogous investigations in humans. In this review, we present behavioural evidence in the form of kinematic analyses suggesting that the cortical circuits responsible for reach-to-grasp actions in humans are organized in a similar fashion. Grasp-to-eat movements are produced with significantly smaller and more precise maximum grip apertures (MGAs) than are grasp-to-place movements directed toward the same objects, despite near identical mechanical requirements of the two subsequent (i.e., grasp-to-eat and grasp-to-place) movements. Furthermore, the fact that this distinction is limited to right-handed movements suggests that the system governing reach-to-grasp movements is asymmetric. We contend that this asymmetry may be responsible, at least in part, for the preponderance of right-hand dominance among the global population.

Hear speech, change your reach: changes in the left-hand grasp-to-eat action during speech processing

Research has shown that the kinematic characteristics of right-hand movements change when executed during both speech production and processing. Despite the variety of prehension and manual actions used to examine this relationship, the literature has yet to examine potential movement effects using an action with a distinct kinematic signature: the hand-to-mouth (grasp-to-eat) action. In this study, participants performed grasp-to-eat and grasp-to-place actions in (a) a quiet environment and (b) while processing speech. Results during the quiet condition replicated the previous findings; consistently smaller grasp-to-eat (compared to grasp-to-place), maximum grip apertures appeared only when using the right hand. Interestingly, in the listen condition, smaller maximum grip apertures in the grasp-to-eat movement appeared in both the right and left hands, despite the fact that participants were right-handed. This paper addresses these results in relation with similar behaviour observed in children, and discusses implications for functional lateralization and neural organization.

Sensorimotor lateralization scaffolds cognitive specialization

In this chapter, we review hemispheric differences for sensorimotor function and cognitive abilities. Specifically, we examine the left-hemisphere specialization for visuomotor control and its interplay with language, executive function, and musical training. Similarly, we discuss right-hemisphere lateralization for haptic processing and its relationship to spatial and numerical processing. We propose that cerebral lateralization for sensorimotor functions served as a foundation for the development of higher cognitive abilities and their hemispheric functional specialization. We further suggest that sensorimotor and cognitive functions are inextricably linked. Based on the studies discussed in this chapter our view is that sensorimotor control serves as a loom upon which the fibers of language, executive function, spatial, and numerical processing are woven together to create the fabric of cognition.

Wait wait, don't tell me: Handedness questionnaires do not predict hand preference for grasping

Handedness questionnaires are a common screening tool in psychology and neuroscience, used whenever a participant's performance on a given task may conceivably be affected by their laterality. Two widely-used examples of such questionnaires are the Edinburgh Handedness Inventory and the Waterloo Handedness Questionnaire. Both instruments ask respondents to report their hand preference for performing a variety of common tasks (e.g., throwing a ball, or opening a drawer). Here we combined questions from the two instruments (E-WHQ; 22 questions total) and asked participants to report their preferred hand for each via a five-point scale. The purpose of this study was to determine whether responses on the E-WHQ are accurate, reliable, and/or predictive of hand-preference for a simple grasp-to-construct task. Regarding accuracy, handedness scores were 5% lower when participants used a scrambled response key versus a consistent one. Test-retest reliability of the questionnaire was weak, with any given inventory item eliciting a different response from 34% of respondents upon retesting. Neither was the E-WHQ predictively useful-although both left- and right-handers preferred their dominant hands, E-WHQ score did not correlate with overall percentage of dominant-hand grasps in either group. We conclude that the E-WHQ is unsuited for predicting hand preference for grasping.

Kinematics of ventrally mediated grasp-to-eat actions: right-hand advantage is dependent on dorsal stream input

Studies have suggested a left-hemisphere specialization for visually guided grasp-to-eat actions by way of task-dependent kinematic asymmetries (i.e., smaller maximum grip apertures for right-handed grasp-to-eat movements than for right-handed grasp-to-place movements or left-handed movements of either type). It is unknown, however, whether this left-hemisphere/right-hand kinematic advantage is reliant on the dorsal "vision-for-action" visual stream. The present study investigates the kinematic differences between grasp-to-eat and grasp-to place actions performance during closed-loop (i.e., dorsally mediated) and open-loop delay (i.e., ventrally mediated) conditions. Twenty-one right-handed adult participants were asked to reach to grasp small food items to (1) eat them, or (2) place them in a container below the mouth. Grasps were performed in both closed-loop and open-loop delay conditions, in separate sessions. We show that participants displayed the right-hand grasp-to-eat kinematic advantage in the closed-loop condition, but not in the open-loop delay condition. As no task-dependent kinematic differences were found in ventrally mediated grasps, we posit that the left-hemisphere/right-hand advantage is dependent on dorsal stream processing.

Articulation Speaks to Executive Function: An Investigation in 4- to 6-Year-Olds

Executive function (EF) and language learning play a prominent role in early childhood development. Empirical research continues to point to a concurrent relation between these two faculties. What has been given little attention, however, is the association between EF and speech articulation abilities in children. This study investigated this relation in children aged 4-6 years. Significant correlations indicated that children with better EF [via parental report of the Behavior Rating Inventory of Executive Function (BRIEF) inventory] exhibited stronger speech sound production abilities in the articulation of the "s" and "sh" sounds. Furthermore, regression analyses revealed that the Global Executive Composite (GEC) of EF as measured by the BRIEF, served as a predictor for speech sound proficiency and that speech sound proficiency served as a predictor for the GEC. Together, these results demonstrate the imbricated nature of EF and speech sound production while bearing theoretical and practical implications. From a theoretical standpoint, the close link between EF and speech articulation may indicate a common ontogenetic pathway. From a practical perspective, the results suggest that children with speech difficulties could be at higher risk for EF deficits.

The contributions of vision and haptics to reaching and grasping

This review aims to provide a comprehensive outlook on the sensory (visual and haptic) contributions to reaching and grasping. The focus is on studies in developing children, normal, and neuropsychological populations, and in sensory-deprived individuals. Studies have suggested a right-hand/left-hemisphere specialization for visually guided grasping and a left-hand/right-hemisphere specialization for haptically guided object recognition. This poses the interesting possibility that when vision is not available and grasping relies heavily on the haptic system, there is an advantage to use the left hand. We review the evidence for this possibility and dissect the unique contributions of the visual and haptic systems to grasping. We ultimately discuss how the integration of these two sensory modalities shape hand preference.

Evidence for right-hand feeding biases in a left-handed population

We have recently shown that actions with similar kinematic requirements, but different end-state goals may be supported by distinct neural networks. Specifically, we demonstrated that when right-handed individuals reach-to-grasp food items with intent to eat, they produce smaller maximum grip apertures (MGAs) than when they grasp the same item with intent to place it in a location near the mouth. This effect was restricted to right-handed movements; left-handed movements showed no difference between tasks. The current study investigates whether (and to which side) the effect may be lateralized in left-handed individuals. Twenty-one self-identified left-handed participants grasped food items of three different sizes while grasp kinematics were captured via an Optotrak Certus motion capture array. A main effect of task was identified wherein the grasp-to-eat action generated significantly smaller MGAs than did the grasp-to-place action. Further analysis revealed that similar to the findings in right-handed individuals, this effect was significant only during right-handed movements. Upon further inspection however, we found individual differences in the magnitude and direction of the observed lateralization. These results underscore the evolutionary significance of the grasp-to-eat movement in producing population-level right-handedness in humans as well as highlighting the heterogeneity of the left-handed population.

Eating interrupted: the effect of intent on hand-to-mouth actions

Evidence from recent neurophysiological studies on nonhuman primates as well as from human behavioral studies suggests that actions with similar kinematic requirements but different end-state goals are supported by separate neural networks. It is unknown whether these different networks supporting seemingly similar reach-to-grasp actions are lateralized, or if they are equally represented in both hemispheres. Recently published behavioral evidence suggests certain networks are lateralized to the left hemisphere. Specifically, when participants used their right hand, their maximum grip aperture (MGA) was smaller when grasping to eat food items than when grasping to place the same items. Left-handed movements showed no difference between tasks. The present study investigates whether the differences between grasp-to-eat and grasp-to-place actions are driven by an intent to eat, or if placing an item into the mouth (sans ingestion) is sufficient to produce asymmetries. Twelve right-handed adults were asked to reach to grasp food items to 1) eat them, 2) place them in a bib, or 3) place them between their lips and then toss them into a nearby receptacle. Participants performed each task with large and small food items, using both their dominant and nondominant hands. The current study replicated the previous finding of smaller MGAs for the eat condition during right-handed but not left-handed grasps. MGAs in the eat and spit conditions did not significantly differ from each other, suggesting that eating and bringing a food item to the mouth both utilize similar motor plans, likely originating within the same neural network. Results are discussed in relation to neurophysiology and development.