Hand Skill Asymmetry in Professional Musicians

Hand skill asymmetry on two handedness tasks was examined in consistent right-handed musicians and nonmusicians as well as mixed-handed and consistent left-handed nonmusicians. Musicians, although demonstrating right-hand superiority, revealed a lesser degree of hand skill asymmetry than consistent right-handed nonmusicians. Increased left-hand skill in musicians accounted for their reduced asymmetry. Musicians predominantly playing keyboard instruments demonstrated superior tapping performance than musicians playing predominantly string instruments, although they did not differ with respect to hand skill asymmetry. Since the diminished tapping asymmetry in musicians was related to early commencement but not duration of musical training, results are interpreted as an adaptation process due to performance requirements interacting with cerebral maturation during childhood.     

Motor planning and execution in left- and right-handed individuals during a bimanual grasping and placing task

The issue of handedness has been the topic of great interest for researchers in a number of scientific domains. It is typically observed that the dominant hand yields numerous behavioral advantages over the non-dominant hand during unimanual tasks, which provides evidence of hemispheric specialization. In contrast to advantages for the dominant hand during motor execution, recent research has demonstrated that the right hand has advantages during motor planning (regardless of handedness), indicating that motor planning is a specialized function of the left hemisphere. In the present study we explored hemispheric advantages in motor planning and execution in left- and right-handed individuals during a bimanual grasping and placing task. Replicating previous findings, both motor planning and execution was influenced by object end-orientation congruency. In addition, although motor planning (i.e., end-state comfort) was not influenced by hand or handedness, motor execution differed between left and right hand, with shorter object transport times observed for the left hand, regardless of handedness. These results demonstrate that the hemispheric advantages often observed in unimanual tasks do not extend to discrete bimanual tasks. We propose that the differences in object transport time between the two hands arise from overt shifting visual fixation between the two hands/objects.     

Atypical speech lateralization in adults with developmental coordination disorder demonstrated using functional transcranial Doppler ultrasound

Research using clinical populations to explore the relationship between hemispheric speech lateralization and handedness has focused on individuals with speech and language disorders, such as dyslexia or specific language impairment (SLI). Such work reveals atypical patterns of cerebral lateralization and handedness in these groups compared to controls. There are few studies that examine this relationship in people with motor coordination impairments but without speech or reading deficits, which is a surprising omission given the prevalence of theories suggesting a common neural network underlying both functions. We use an emerging imaging technique in cognitive neuroscience; functional transcranial Doppler (fTCD) ultrasound, to assess whether individuals with developmental coordination disorder (DCD) display reduced left‐hemisphere lateralization for speech production compared to control participants. Twelve adult control participants and 12 adults with DCD, but no other developmental/cognitive impairments, performed a word‐generation task whilst undergoing fTCD imaging to establish a hemispheric lateralization index for speech production. All participants also completed an electronic peg‐moving task to determine hand skill. As predicted, the DCD group showed a significantly reduced left lateralization pattern for the speech production task compared to controls. Performance on the motor skill task showed a clear preference for the dominant hand across both groups; however, the DCD group mean movement times were significantly higher for the non‐dominant hand. This is the first study of its kind to assess hand skill and speech lateralization in DCD. The results reveal a reduced leftwards asymmetry for speech and a slower motor performance. This fits alongside previous work showing atypical cerebral lateralization in DCD for other cognitive processes (e.g., executive function and short‐term memory) and thus speaks to debates on theories of the links between motor control and language production.     

Effects of an Occupational Therapy Hand Dominance Transfer Intervention for Soldiers With Crossed Hand-Eye Dominance

Crossed dominance (CD) is defined as an individual's dominant hand and dominant eye being on opposite sides of the body. CD negatively impacts an individual's ability to accurately aim and fire long-barreled guns. The authors developed and evaluated a hand dominance transfer (HDT) intervention to improve the M16 rifle shooting accuracy, efficiency, and skill transfer. Twenty-four U.S. Army soldiers with CD were taught how to handle and fire an M16 rifle using the nondominant hand. Training was conducted at a military, indoor laser-equipped weapons simulator. Accuracy for shooting 40 rounds at baseline with the nondominant eye and dominant hand (NDE/DH) was 22.12 compared to shooting 30.46 with the dominant eye and nondominant hand (DE/NDH). This difference was statistically significant with p = .000. The transfer of shooting accuracy skill (retention) following the HDT intervention was 33.42 with a comparative p value of .100. Efficiency of shooting 10 rounds at baseline with the NDE/DH was 6.3 compared to shooting 7.3 with the DE/NDH. This difference was not statistically significant (p = .107). The transfer of shooting efficiency skill (retention) was 7.96 with a comparative p value of .349. This study supports shooting with the DE/NDH. HDT could be further developed to address the soldiering skill of shooting an M16.     

Right hemisphere specialization for color detection

Three experiments were carried out to investigate hemispheric asymmetry in color processing among normal participants. In Experiment 1, it was shown that the reaction times (RTs) of the dominant and non-dominant hands assessed using a visual target presented at the central visual field, were not significantly different. In Experiment 2, RTs of ipsilateral hands to lateralized chromatic stimuli revealed that the processing time was 17 ms shorter in the right hemisphere (RH) than that in the left hemisphere among the right-handed participants, whereas no significant difference was found among the left-handed participants. On the other hand, RTs to lateralized achromatic stimuli showed no such asymmetry among both the right- and left-handed participants (Experiment 3). These findings strongly suggest RH superiority for detection of color among right-handed individuals.     

The Simon effect and handedness: evidence for a dominant-hand attentional bias in spatial coding

In two experiments, the relation between handedness and the size of the Simon effect in each visual hemifield was investigated. Experiment 1 showed that the Simon effect was larger in the right visual hemifield in right-handers and in the left visual hemifield in left-handers, whereas ambidextrous individuals showed a symmetric Simon effect. In Experiment 2, participants performed the same Simon task as in Experiment 1, but with their hands crossed. The right- and left-handed groups showed a reversed pattern of results with respect to Experiment 1. We explained this phenomenon as a part of a more general account in which perception and action are embedded in a perception-for-action system. In this system, an attentional bias originating from the field of operation of the dominant hand would be at the basis of the relationship between the asymmetry of the Simon effect and handedness.     

Visual versus kinesthetic mental imagery: Efficacy for the retention and transfer of a closed motor skill in young children

The main purposes of this study were (a) to compare the effects of mental imagery combined with physical practise and specific physical practise on the retention and transfer of a closed motor skill in young children; (b) to determine the mental imagery (visual vs. kinesthetic), which is the most efficient for retention and transfer of a closed motor skill; and (c) to verify the relationship between movement image vividness and motor performance. As for the secondary purpose, it was to compare the effects of gender on motor learning. Participants (n = 96) were selected from 3 primary schools. These participants were divided into 6 groups and submitted to different experimental conditions. The experimental task required the participants to throw, with the nondominant hand (left hand), a ball toward a target composed of 3 concentric circles. The results demonstrated that performance obtained by the mental imagery (visual or kinesthetic) combined with physical practise group was, during the retention phase, equivalent to that produced by the specific physical practise group but significantly superior during the transfer of closed motor skill. These results showed the potential benefits of mental imagery as a retention strategy intended for motor skills and performance enhancement. Such results could be explained by the similarity of 3 principal functional evidences shared by mental and physical practise: behavioural, central, and peripheral (as suggested by Holmes & Collins, 2001). (PsycINFO Database Record (c) 2008 APA, all rights reserved).     

The influence of attentional focus on the development of skill representation in a complex action

ObjectivesRecent research has indicated that performers' mental representation of a motor skill changes over the course of learning. In the present study, we sought to ascertain whether the type of instructions (instructions that emphasize either an internal or external focus of attention) influences the development of skill representation during motor learning.DesignParticipants without golf experience were recruited to practice a golf putting task over the course of three training days. Participants were randomly assigned to either an internal focus (focus on the swing of the arms; n = 10) or external focus (focus on the speed of the ball roll; n = 10) learning group. Changes in putting performance and mental representation structure were assessed over the course of learning, as well as during a follow-up retention test two days after practice.MethodsMental representation structure was measured employing the structural dimensional analysis of mental representations (SDA-M), which provided psychometric data on the structure of the mental representation in long-term memory. Additionally, the change in putting accuracy and consistency was recorded over the course of learning.ResultsFindings indicated that the external focus group performed with greater accuracy and consistency during training, and revealed a larger degree of development in their mental representation of the putting task.ConclusionsOverall, our findings suggest that facilitating the link between an action and its effect by means of an external focus is crucial for motor performance as well as the development of skill representation.     

Hale-Bopp and Handedness: Individual Differences in Memory for Orientation

The accuracy with which a person recalls the orientation of a human figure or head has been shown to depend systematically on the person's handedness. This study investigated whether memory for the orientation of an inanimate object displays a similar effect. In contrast to previous work investigating memory for depictions encountered over many years, the present work focused on memory for a unique event that engaged considerable attention over a relatively brief period—Comet Hale-Bopp. The results showed that although right-handed and left-handed individuals did not differ in their memory for semantic information concerning the comet, they did differ in their memory for its orientation. Right-handed people were significantly more likely than left-handed people both to recall and to recognize the comet as facing to the left. The results suggest that memory performance may be influenced by patterns of underlying cerebral motor activation.     

Children's motor imagery modality dominance modulates the role of attentional focus in motor skill learning

We investigated whether children's motor imagery dominance modulated the relationship between attentional focus and motor learning of a tossing task. One hundred and thirty-eight boys (age: M = 10.13, SD = 0.65) completed the Movement Imagery Questionnaire – Children (MIQ-C) to determine imagery modality dominance (kinesthetic, internal-visual, external-visual) and were randomly assigned to either an internal (n = 71) or external (n = 67) attentional focus group. Participants completed 60 trials of a tossing task with their non-dominant hand on day 1. Participants in the internal focus group were asked “to focus on the throwing arm”, whereas participants in the external focus group were instructed “to focus on the ball.” A retention test was conducted 24 h later to assess motor learning. Overall, the results from a nested, multiple linear regression analysis indicated the degree to which internal or external focus influences children's throwing accuracy is dependent upon their motor imagery modality dominance. Specifically, higher levels of external-visual imagery dominance resulted in greater motor learning for children adopting an external focus. In contrast, higher values of kinesthetic imagery dominance resulted in reduced motor learning for children who adopted an external focus. Despite the need for future research, we recommend motor imagery modality dominance assessments be considered when investigating the influence of attentional focus on motor learning, particularly when the target population is children.     

Control of interjoint coordination in the performance of manual circular movements can explain lateral specialization

Between-arm performance asymmetry can be seen in different arm movements requiring specific interjoint coordination to generate the desired hand trajectory. In the current investigation, we assessed between-arm asymmetry of shoulder-elbow coordination and its stability in the performance of circular movements. Participants were 16 healthy right-handed university students. The task consisted of performing cyclic circular movements with either the dominant right arm or the nondominant left arm at movement frequencies ranging from 40% of maximum to maximum frequency in steps of 15%. Kinematic analysis of shoulder and elbow motions was performed through an optoelectronic system in the three-dimensional space. Results showed that as movement frequency increased circularity of left arm movements diminished, taking an elliptical shape, becoming significantly different from the right arm at higher movement frequencies. Shoulder-elbow coordination was found to be asymmetric between the two arms across movement frequencies, with lower shoulder-elbow angle coefficients and higher relative phase for the left compared to the right arm. Results also revealed greater variability of left arm movements in all variables assessed, an outcome observed from low to high movement frequencies. From these findings, we propose that specialization of the left cerebral hemisphere for motor control resides in its higher capacity to generate appropriate and stable interjoint coordination leading to the planned hand trajectory.     

Unilateral implicit motor learning deficit in developmental dyslexia

It has been suggested that developmental dyslexia involves various literacy, sensory, motor skill, and processing speed deficits. Some recent studies have shown that individuals with developmental dyslexia exhibit implicit motor learning deficits, which may be related to cerebellar functioning. However, previous studies on implicit motor learning in developmental dyslexics have produced conflicting results. Findings from cerebellar lesion patients have shown that patients' implicit motor learning performance varied when different hands were used to complete tasks. This suggests that dyslexia may have different effects on implicit motor learning between the two hands if cerebellar dysfunction is involved. To specify this question, we used a one-handed version of a serial reaction time task to compare the performance of 27 Chinese children with developmental dyslexics with another 27 age-matched children without reading difficulties. All the subjects were students from two primary schools, Grades 4 to 6. The results showed that children with developmental dyslexic responded more slowly than nondyslexic children, and exhibited no implicit motor learning in the condition of left-hand response. In contrast, there was no significant difference in reaction time between two groups of children when they used the right hand to respond. This finding indicates that children with developmental dyslexia exhibited normal motor skill and implicit motor learning ability provided the right hand was used. Taken together, these results suggested that Chinese children with developmental dyslexia exhibit unilateral deficits in motor skill and implicit motor learning in the left hand. Our findings lend partial support to the cerebellar deficit theory of developmental dyslexia.     

Hemispheric specialization for emotional word processing is a function of SSRI responsiveness

Vulnerability to depression and non-response to Selective Serotonin Reuptake Inhibitors (SSRIs) are associated with specific neurophysiological characteristics including greater right hemisphere (RH) relative to left hemisphere (LH) activity. The present study investigated the relationship between hemispheric specialization and processing of emotional words using a divided visual field paradigm administered to never-depressed and previously-depressed individuals, who were subdivided into SSRI responders and non-responders. SSRI responders and never-depressed participants were similar in their left hemispheric lateralization for evaluating emotional words. In contrast, SSRI non-responders showed a relative shift towards RH processing of negative words, and a strong bias toward negative evaluation of words presented to the RH. The results are discussed within the context of a biological-cognitive model of vulnerability to depression.     

Behavioral asymmetries of psychomotor performance in rhesus monkeys (Macaca mulatta): a dissociation between hand preference and skill.

Hand preferences were recorded for 35 rhesus monkeys (Macaca mulatta) as they manipulated a joystick in response to 2 computerized tasks. These preferences were then used to contrast 8 left- and 10 right-handed subjects on performance measures of hand skill. Individual hand preferences were found, but no significant population asymmetry was observed across the sample. However, the performance data reveal substantial benefits of right-handedness for joystick manipulation, as this group of monkeys mastered the 2 psychomotor tasks significantly faster than did their left-handed counterparts. The data support earlier reports of a right-hand advantage for joystick manipulation and also support the importance of distinguishing between hand preference and manual performance in research on functional asymmetries.     

Hemispheric specialization for emotional word processing is a function of SSRI responsiveness

Vulnerability to depression and non-response to Selective Serotonin Reuptake Inhibitors (SSRIs) are associated with specific neurophysiological characteristics including greater right hemisphere (RH) relative to left hemisphere (LH) activity. The present study investigated the relationship between hemispheric specialization and processing of emotional words using a divided visual field paradigm administered to never-depressed and previously-depressed individuals, who were subdivided into SSRI responders and non-responders. SSRI responders and never-depressed participants were similar in their left hemispheric lateralization for evaluating emotional words. In contrast, SSRI non-responders showed a relative shift towards RH processing of negative words, and a strong bias toward negative evaluation of words presented to the RH. The results are discussed within the context of a biological–cognitive model of vulnerability to depression.     

Pitch and timing abilities in adult left-hemisphere-dysphasic and right-hemisphere-damaged subjects

The production and perception of pitch and rhythm were tested in patients with acquired unilateral left-hemisphere (LH) lesions (and subsequent motor dysphasia, n = 13), patients with unilateral right-hemisphere (RH) lesions (n = 14), and normal age-matched controls. While the LH dysphasic subjects were not generally impaired on the production or perception of pitch, they were grossly impaired on the production and perception of rhythm. The RH subjects, in contrast, were impaired on measures of pitch perception and production, including the discrimination and production of single notes and of melodies. It is concluded that the two hemispheres differ in their specialization for the perception and production of pitch and rhythm.     

Inconsistent handedness is linked to more successful foreign language vocabulary learning

The study examined correlations between incidental learning of foreign words and interhemispheric connectivity, operationalized as consistency of hand preference, using pooled data of five experiments on adult foreign language learning (N=242). Inconsistent hand preference was found to be positively correlated with vocabulary learning even after effects of cognitive variables (verbal working memory capacity and nonverbal IQ), identified previously as predictive of successful foreign-language vocabulary learning, were partialled out. This observed relationship between handedness consistency and vocabulary learning persisted when left-handed and right-handed individuals were analyzed separately, and there was no overall difference in performance between left- and right-handers. The findings confirm an association between degree of handedness and verbal episodic memory.     

The Specificity of Motor Skill and Manual Asymmetry: A Review of the Evidence and Its Implications

Results of investigations on gaining control of limb movements are reviewed, and their contribution to understanding the development of manual asymmetries is discussed in relation to the discrimination and programming of appropriate neuromuscular resources. An examination of the relevant evidence on number and types of manual asymmetries recorded provides strong grounds for concluding that where asymmetries occur, they simply represent a further example of the well-documented activity-specific nature of motor skills and of the extremely lengthy periods of learning or experience needed for their acquisition and perfection. This specificity of motor skill and manual asymmetry also readily accounts for most of the discrepancy usually reported between assessments of hand preference and performance differences between hands, because these alternative measures of handedness have rarely employed the same range or variety of tasks.     

Laterally focused attention modulates asymmetric coupling in rhythmic interlimb coordination

Peters (J Motor Behav 21:151-155, 1989; Interlimb coordination: neural, dynamical and cognitive constraints, Academic, Orlando, pp 595-615, 1994) suggested that expressions of handedness in bimanual coordination may be reflections of an inherent attentional bias. Indeed, previous results indicated that focusing attention on one of the limbs affected the relative phasing between the limbs in a manner comparable to the effects of hand dominance. The present study extended the comparison between the effects of attentional focus and handedness by testing their impact on the interactions between the limbs. Both left-handed and right-handed participants performed rhythmic bimanual coordination tasks (in-phase and antiphase coordination), while directing attention to either limb. Using brief mechanical perturbations, the degree to which the limbs were influenced by each other was determined. The results revealed that the non-dominant limb was more strongly affected by the dominant limb than vice versa and that, in line with Peters' proposition, this handedness-related asymmetry in coupling strength was reduced when attention was focused on the non-dominant limb, thereby highlighting the potential relation between inherent (handedness-related) asymmetries and voluntary attentional asymmetries. In contrast to previous findings, the (commonly observed) phase lead of the dominant limb was attenuated (rather than accrued) when attention was focused on this limb. This unexpected result was explained in terms of the observed attention-related difference in amplitude between the limbs.     

Spatial ability and handedness

The relationship between preferred handedness and spatial visualization was examined for 124 female and 229 male undergraduate students. Handedness and spatial ability were used in the design as continuous variables. Other variables examined were sex of subject and family history of sinistrality. Spatial ability was found to be systematically related to measured handedness, familial left-handedness, and sex of subject. Males outperformed females at all levels of handedness. The lowest performance was obtained by subjects who were either extremely left-handed or extremely right-handed. The highest scores were obtained by individuals with left-handed relatives and whose handedness scores were in the range considered mixed or slightly right-handed. The results suggest that decreased hemispheric specialization is associated with increased spatial ability.