Skilled Hand Use Research Articles

Early, concurrent, and consistent hand preferences predict stacking in toddlerhood.

Stacking is a hallmark of fine motor skill development and requires skilled hand use. One mechanism for children to gain manual proficiency involves establishing a hand preference that creates practice differences between the hands as the preferred hand is used more often and in different ways than the other. Prior work found that stacking skill emerged earlier for infants with an identifiable hand preference. However, it is not known how hand preference relates to later toddler stacking performance. This study examined the effects of early hand preference (infant pattern), concurrent hand preference (toddler pattern), and consistent hand preference (infant to toddler pattern) on toddler stacking skills. Sixty-one toddlers, whose hand preferences as infants were known, were assessed for their toddler hand preference and their stacking skill across 7monthly visits from 18 to 24months of age. Using multilevel Poisson longitudinal analysis, children with hand preferences that were consistent across both infancy and toddlerhood were more successful at stacking, compared to those with inconsistent preferences across the infant and toddler periods. Thus, consistency of hand preferences during the first 2years likely contributes toward individual differences in the development of fine motor skills.

Prehensile kinematics of the marmoset monkey: Implications for the evolution of visually-guided behaviors.

Throughout the primate lineage, there is a wide diversity of prehensile capacity that is thought to stem from individual species foraging patterns. While many studies have explored primates with precise hand grips, such as higher apes, few have considered primates that lack opposition movements. The New World marmoset monkey occupies an intriguing niche, displaying adept control of their hand movements yet their absence of opposable digits results in relatively imprecise grasping actions when compared with those observed in Old World monkeys, apes, and humans. The marmoset monkey offers a unique composition of ancestral primate corticospinal organization combined with skilled hand use to explore the evolution and development of visually-guided actions. In this study, four adult marmosets were trained to perform a series of visually-guided tasks, designed to assess their control over locating and retrieving objects of differing dimensions. Two of these animals received a neonatal lesion of the inferior pulvinar (unilateral), a thalamic nucleus previously demonstrated to be involved in visuomotor development. The kinematics of their reaching and grasping patterns were recorded for offline analysis. Predictive modeling revealed that maximum grip aperture, time to reach peak velocity and hand use were reliable predictors of distinguishing between cohorts. A consistent feature observed across all tasks was that they do not precisely scale their grip according to the dimensions of the target object which may be attributed to their lack of independent digit control. Therefore, the marmoset monkey represents a previously understudied position in the evolution of primate reach and grasp behavior.

The BACHD Rat Model of Huntington Disease Shows Specific Deficits in a Test Battery of Motor Function.

Rationale: Huntington disease (HD) is a progressive neurodegenerative disorder characterized by motor, cognitive and neuropsychiatric symptoms. HD is usually diagnosed by the appearance of motor deficits, resulting in skilled hand use disruption, gait abnormality, muscle wasting and choreatic movements. The BACHD transgenic rat model for HD represents a well-established transgenic rodent model of HD, offering the prospect of an in-depth characterization of the motor phenotype.Objective: The present study aims to characterize different aspects of motor function in BACHD rats, combining classical paradigms with novel high-throughput behavioral phenotyping.Methods: Wild-type (WT) and transgenic animals were tested longitudinally from 2 to 12 months of age. To measure fine motor control, rats were challenged with the pasta handling test and the pellet reaching test. To evaluate gross motor function, animals were assessed by using the holding bar and the grip strength tests. Spontaneous locomotor activity and circadian rhythmicity were assessed in an automated home-cage environment, namely the PhenoTyper. We then integrated existing classical methodologies to test motor function with automated home-cage assessment of motor performance.Results: BACHD rats showed strong impairment in muscle endurance at 2 months of age. Altered circadian rhythmicity and locomotor activity were observed in transgenic animals. On the other hand, reaching behavior, forepaw dexterity and muscle strength were unaffected.Conclusions: The BACHD rat model exhibits certain features of HD patients, like muscle weakness and changes in circadian behavior. We have observed modest but clear-cut deficits in distinct motor phenotypes, thus confirming the validity of this transgenic rat model for treatment and drug discovery purposes.

Anatomical changes in the somatosensory system after large sensory loss predict strategies to promote functional recovery after spinal cord injury.

Among cases of spinal cord injury are injuries involving the dorsal column in the cervical spinal cord that interrupt the major cutaneous afferents from the hand to the cuneate nucleus (Cu) in the brainstem. Deprivation of touch and proprioceptive inputs consequently impair skilled hand use. Although dexterous hand use can be significantly restored in some patients after months of recovery, some patients never fully recover from the injury. Patients also may develop painful and nonpainful phantom sensations (Moore et al., 2000). Such differences in recovery are often attributed, in part, to differences in the level and extent of the injury. However, specific relationships between individual injuries and indicators of recovery require intensive study. Due to the similarities of the nervous system in humans and nonhuman primates, research in monkeys greatly advances the understanding of relationships between injury and plasticity in human brains that contribute to functional recoveries.

The contribution of the reach and the grasp to shaping brain and behaviour.

Skilled hand use is a striking feature of human behaviour, but in contrast to the view that it recently evolved in the primate lineage, the present paper argues that skilled hand movements have an early phylogenetic origin dating back to the synergies displayed by the pectoral fins of bony fishes. Insights into the function and evolution of hand use stem from the dual visuomotor channel theory, which proposes that prehension is a composite of 2 movements, the reach and the grasp. The reach is in part an egocentric act directed toward the extrinsic (location) features of objects while the grasp is in part an allocentric act directed toward the intrinsic (shape and size) features of objects. Phylogenetic, developmental, and behavioural evidence suggest that the reach and the grasp evolved separately under somatosensory control and were subsequently coordinated with visual control in the primate lineage. Accordingly, parallel pathways from visual cortex came to influence separate reach and grasp systems in parietofrontal cortex, and new descending pathways to the spinal cord came to assist in visually guided reaching. Neural processes related to the "where" of the reach and the "what" of the grasp have had a formative role in shaping cognition more generally.

Bihemispheric Anodal Corticomotor Stimulation Using Transcranial Direct Current Stimulation Improves Bimanual Typing Task Performance

ABSTRACT Transcranial direct current stimulation (tDCS) is associated with improved unimanual skilled hand use. The authors assessed effects of bihemispheric anodal corticomotor tDCS (BAC-tDCS) on bimanual skilled hand use. Twenty-eight nondisabled subjects were randomized to either BAC-tDCS or sham-tDCS, 20 min daily for 5 consecutive days. Performance on a bimanual typing (BT) task and a short-term memory (STM) task was assessed daily and at 1-week follow-up. Mean change between Day 1 and Day 5 in BT score with BAC-tDCS (19.4 points; 95% CI [12.82, 25.99]) was significantly greater (p =.04) than change with sham-tDCS (12.5 points; 95% CI [7.6, 17.3]). Neither group retained improvements in BT score at follow-up. BAC-tDCS had no effect on STM. These results may have implications for interventions to improve hand function in persons with bilateral hand dysfunction.

Laterality affects spontaneous recovery of contralateral hand motor function following motor cortex injury in rhesus monkeys

The purpose of this study was to test whether brain laterality influences spontaneous recovery of hand motor function after controlled brain injuries to arm areas of M1 and lateral premotor cortex (LPMC) of the hemisphere contralateral to the preferred hand in rhesus monkeys. We hypothesized that monkeys with stronger hand preference would exhibit poorer recovery of skilled hand use after such brain injury. Degree of handedness was assessed using a standard dexterity board task in which subjects could use either hand to retrieve small food pellets. Fine hand/digit motor function was assessed using a modified dexterity board before and after the M1 and LPMC lesions in ten monkeys. We found a strong negative relationship between the degree of handedness and the recovery of manipulation skill, demonstrating that higher hand preference was associated with poorer recovery of hand fine motor function. We also observed that monkeys with larger lesions within M1 and LPMC had greater initial impairment of manipulation and poorer recovery of reaching skill. We conclude that monkeys with a stronger hand preference are likely to show poorer recovery of contralesional hand fine motor skill after isolated brain lesions affecting the lateral frontal motor areas. These data may be extended to suggest that humans who exhibit weak hand dominance, and perhaps individuals who use both hands for fine motor tasks, may have a more favorable potential for recovery after a unilateral stroke or brain injury affecting the lateral cortical motor areas than individuals with a high degree of hand dominance.

A framework of children's hand skills for assessment and intervention

BACKGROUND; Hand skill development or mastery has a huge influence on children's early development and participation in everyday activities. Assessment of difficulties with children's hand skills typically involves a systematic process considering all potential factors that may impact on hand skills. This helps identify key hand skill difficulties and select specific interventions that are relevant to the individual child. This paper describes the development of the Children's Hand Skills Framework (CHSF) that can be used as a conceptual guide to analyse and describe children's hand skills in the assessment and intervention process. A comprehensive literature review of the existing hand skill models and instruments was conducted to develop the CHSF content, and experts' reviews via an evaluation feedback questionnaire were used as a means to validate the CHSF. The literature review revealed that the functional repertoire of children's hand skills can be divided into six distinct categories. Manual gesture and body contact hand skills are two categories, in which the hands do not make contact with any object. Arm-hand use, adaptive skilled hand use and bimanual use are object-related hand skill categories where the hands do contact objects. The final category is related to the general quality of children's hand skills. Each of the six hand skill categories can be further broken down into three to seven subcategories. The feedback from the experts further demonstrated high levels of agreement for the inclusion of the CHSF subcategories. The CHSF offers a helpful guide to comprehensively describe the complexity of children's hand skills in the assessment process and has the potential to enhance and promote communication about functional use of children's hand skills among professionals. The CHSF is also conceptually compatible with the International Classification of Functioning, Disability, and Health, providing a holistic consideration of both children's hand skills and relevant International Classification of Functioning, Disability, and Health factors for further assessment and intervention planning.

Parallel Evolution of Cortical Areas Involved in Skilled Hand Use

Dexterous hands, used to manipulate food, tools, and other objects, are one of the hallmarks of primate evolution. However, the neural substrate of fine manual control necessary for these behaviors remains unclear. Here, we describe the functional organization of parietal cortical areas 2 and 5 in the cebus monkey. Whereas other New World monkeys can be quite dexterous, and possess a poorly developed area 5, cebus monkeys are the only New World primate known to use a precision grip, and thus have an extended repertoire of manual behaviors. Unlike other New World Monkeys, but much like the macaque monkey, cebus monkeys possess a proprioceptive cortical area 2 and a well developed area 5, which is associated with motor planning and the generation of internal body coordinates necessary for visually guided reaching, grasping, and manipulation. The similarity of these fields in cebus monkeys and distantly related macaque monkeys with similar manual abilities indicates that the range of cortical organizations that can emerge in primates is constrained, and those that emerge are the result of highly conserved developmental mechanisms that shape the boundaries and topographic organizations of cortical areas.

Sensorimotor deficits in a unilateral intrastriatal 6-OHDA partial lesion model of Parkinson’s disease in marmoset monkeys

Animal studies investigating the efficacy of neurotrophic factors as treatments for Parkinson’s disease (PD) ideally require partial dopamine (DA) lesion models. The intrastriatal 6-hydroxydopamine (6-OHDA) lesion model may be suitable for this purpose. Although this model has been well characterized in rodents, it has not previously been used in monkeys. The goal of the present study was to characterize the behavioral effects of unilateral injections of 6-OHDA in the basal ganglia of common marmoset monkeys ( Callithrix jacchus). Cell counts from tyrosine hydroxylase immunochemistry 5 months postlesion revealed DA cell loss in the substantia nigra on the lesioned side to ∼46% of relative to the unlesioned side. 6-OHDA lesioned monkeys showed a variety of behavioral deficits. Apomorphine induced rotation and simple sensorimotor measures (head position bias and PD disability rating score) were most affected by the lesion. The largest deficits were seen at 1 or 2 weeks postsurgery but had recovered by week 10. 6-OHDA lesioned monkeys took longer to complete a more complex sensorimotor staircase task. At 3.5 months postlesion, 6-OHDA monkeys also showed deficits on an object retrieval task designed to measure sensorimotor planning and skilled hand use. α-Methyl- p-tyrosine, a tyrosine hydroxylase inhibitor, reinstated those deficits which had undergone recovery in the lesioned animals and also exacerbated the deficits on the staircase task. This model has potential in assessing treatments for PD aimed at curtailing disease progression such as continuous delivery of neurotrophic factors.

How skilled are the skilled limb movements of the raccoon ( Procyon lotor)?

Raccoons have been widely used for neurobiological research and with respect to paw (hand) use have been `considered' to be primates because they display highly developed skilled hand use. Their exceptional manipulatory ability is puzzling from an evolutionary perspective both because they belong to a taxon that is divergent from primates and because most members of their taxon are not especially skilled. Surprisingly, there has been no systematic investigation of their manipulatory ability. This was the purpose of the present study. Captive and zoo-housed raccoons were video recorded during food handling in a wide variety of conditions and the video records were subjected to descriptive frame-by-frame analysis aided by the use of Eshkol–Wachman Movement Notation (EWMN). The results confirm that raccoons display good manual skills in food finding, grasping and handling. Like primates, they use vision to identify and reach for objects, but additionally they make extensive use of haptically controlled movements. Unlike primates, they do not have a true convergent hand as it has limited flexive properties. Objects are grasped between the digits or between the apical digit and distal palmar pads. Manipulation of objects consisted of rolling the object between the palms of both hands, with little or no digit movement. Finally, although they can make unimanual reaching movements, they make extensive use of a bimanual reaching strategy. These results suggest that raccoons are like primates in that they display visual guidance of reaching, but are similar to other carnivores in that they do not use convergent grasping and digit manipulation and frequently use bimanual grasping. The results, consistent with a growing body of information on skilled use in mammals, including marsupials and rodents, suggest that raccoons are specialised, but not special.

Recovery of motor function after focal cortical injury in primates: compensatory movement patterns used during rehabilitative training

The recovery of skilled hand use after cortical injury was assessed in adult squirrel monkeys. Specific movement patterns used to perform a motor task requiring fine manual skill were analyzed before and after a small ischemic infarct (2.6-3.8 mm2) to the electrophysiologically identified hand area of the primary motor cortex (M1). After 1-3 weeks of pre-infarct training, each monkey stereotypically used one specific movement pattern to retrieve food pellets. After injury to the hand area of M1, the monkeys were required to retrieve the pellets using their impaired forelimb. Immediately after the injury, the number of finger flexions used by the monkeys to retrieve the pellets increased, indicating a deficit in skilled finger use. After approximately 1 month of rehabilitative training, skilled use of the fingers appeared to recover, indicated by a reduction in the number of finger flexions per retrieval. The monkeys again retrieved the pellets using one specific movement pattern in most trials. Despite the apparent recovery of skilled finger use after rehabilitative training, three of five monkeys retrieved the pellets using stereotypic movement patterns different from those used before the injury. Thus, this study provides evidence that compensatory movement patterns are used in the recovery of motor function following cortical injury, even after relatively small lesions that produce mild, transient deficits in motor performance. Examination of electrophysiological maps of evoked movements suggests that the mode of recovery (re-acquisition of pre-infarct movement strategies vs development of compensatory movement strategies) may be related to the relative size of the lesion and its specific location within the M1 hand representation.

Neural substrates for the effects of rehabilitative training on motor recovery after ischemic infarct.

Substantial functional reorganization takes place in the motor cortex of adult primates after a focal ischemic infarct, as might occur in stroke. A subtotal lesion confined to a small portion of the representation of one hand was previously shown to result in a further loss of hand territory in the adjacent, undamaged cortex of adult squirrel monkeys. In the present study, retraining of skilled hand use after similar infarcts resulted in prevention of the loss of hand territory adjacent to the infarct. In some instances, the hand representations expanded into regions formerly occupied by representations of the elbow and shoulder. Functional reorganization in the undamaged motor cortex was accompanied by behavioral recovery of skilled hand function. These results suggest that, after local damage to the motor cortex, rehabilitative training can shape subsequent reorganization in the adjacent intact cortex, and that the undamaged motor cortex may play an important role in motor recovery.