Human motor development and hand laterality: a kinematic analysis of drawing movements

The contribution of motor efficiency to drawing performance of older people with and without signs of cognitive decline

In clinical practice, different drawing tests are used for the assessment of cognitive efficiency in the geriatric population. However, so far, the contribution of motor skills to drawing performance has not been sufficiently examined in the late adult life span. This study was aimed at disentangling the role played by motor functioning in three well-known drawing tests that in the clinical field are commonly used to detect some signs of cognitive impairment of older individuals. One hundred and forty-nine community dwellers (M_age = 77.4 years, SD = 5.9 years) completed a battery of tests assessing global cognitive efficiency, drawing skills (i.e., Clock Drawing, Visuo-spatial Drawing ACE-R, Copy Figures Tests), handgrip muscular strength (HGS), and functional mobility (assessed through the Timed-Up-and-Go test). Significant relationships were found among those measures. Moreover, handgrip strength and functional mobility explained 12-19% of the variance in each drawing condition. Finally, participants exhibiting poorer HGS performed worse the drawing tasks and were successively recognized as cognitively deteriorated. In conclusion, these findings highlight that motor skills can significantly impact the assessment of cognitive efficiency in late adulthood. Therefore, in clinical practice, the concurrent assessment of basic motor functions (in terms of muscular strength and functional mobility) and cognitive efficiency of the geriatric population at risk for cognitive decline should be encouraged.

Handwriting kinematics during learning to write with the dominant left hand in converted left-handers

Converting left-handers to their non-dominant right hand was previously widespread, particularly for handwriting. The present study aimed to explore the extent to which adult, converted left-handers can learn writing with their dominant left hand during a 2-year training program. Eleven converted left-handers participated in the training. Handwriting kinematics were assessed at regular intervals (seven sessions) and compared to those of 11 innate left-handed controls matched for age, gender, and overall handedness score for basic (Finger, Wrist, Circle) and complex (Sentence, Copy) handwriting tasks. Regarding basic tasks in the training group, we found rapid increases in left and right-hand frequency and no significant differences between both hands at any time point, indicating successful hand transfer. After 24 months, training participants significantly surpassed controls for writing frequency in basic tasks with their left hand. For complex tasks, we identified significant increases in the training groups' left-hand writing frequency and duration between the first and last session. While training participants' left-hand writing remained significantly slower than their right-hand writing, statistics confirmed final differences between hands only for the duration of the Sentence task. Importantly, left-hand writing in the training group was characterized by lower frequency, lower automaticity, and prolonged duration after 24 months compared to innate left-handers. With training participants' left-hand writing skills significantly increasing for complex tasks and no final statistically significant differences between hands for frequency and automaticity, the program was considered effective. Nevertheless, within 2 years, training participants did not reach innate left-handers handwriting proficiency for complex tasks. Underlying reasons may be various, such as a non-optimal training program, a sensitive period for learning to write, irreversible neural changes during conversion in childhood, age-related decline of motor learning capacity, or retrograde interference between right- and left-hand writing.

The motor Wisdom of the Crowd

Wisdom of the Crowd is the aggregation of many individual estimates to obtain a better collective one. Because of its enormous social potential, this effect has been thoroughly investigated, but predominantly on tasks that involve rational thinking (such as estimating a number). Here we tested this effect in the context of drawing geometrical shapes, which still enacts cognitive processes but mainly involves visuomotor control. We asked more than 700 school students to trace five patterns shown on a touchscreen and then aggregated their individual trajectories to improve the match with the original pattern. Our results show the characteristics of the strongest examples of Wisdom of the Crowd. First, the aggregate trajectory can be up to 5 times more accurate than the individual ones. Second, this great improvement requires aggregating trajectories from different individuals (rather than trials from the same individual). Third, the aggregate trajectory outperforms more than 99% of individual trajectories. Fourth, while older individuals outperform younger ones, a crowd of young individuals outperforms the average older one. These results demonstrate for the first time Wisdom of the Crowd in the realm of motor control, opening the door to further studies of human and also animal behavioural trajectories and their mechanistic underpinnings.

Integration of Speed and Quality in Measuring Graphomotor Skills: The Zurich Graphomotor Test

IMPORTANCE

In educational settings, children are under pressure to finish their work successfully within required time frames. Existing tools for assessing graphomotor skills measure either quality or speed of performance, and the speed-accuracy trade-off (SAT) in such tools has never been investigated.

OBJECTIVE

We aimed to evaluate a newly developed tool for measuring graphomotor skills, the Zurich Graphomotor Test (ZGT), that assesses both speed and quality of performance. We also explored whether graphomotor tests are affected by the SAT and, if so, the effects it has on graphomotor test results.

DESIGN

Cross-sectional study.

SETTING

Educational institutions in Switzerland.

PARTICIPANTS

Children, adolescents, and young adults (N = 547) ages 4-22 yr (50.3% female).

OUTCOMES AND MEASURES

Graphomotor performance was measured with the ZGT and the Developmental Test of Visual Perception, Second Edition (DVTP-2). Standard deviation scores were used to quantify performance. We combined ZGT speed and quality measurements into a performance score adjusted for age and sex.

RESULTS

ZGT results indicated a marked developmental trend in graphomotor performance; older children were faster than younger children. Girls showed higher overall performance than boys. The pattern of making more mistakes when being faster and making fewer mistakes when being slower was observed for both graphomotor tests, regardless of time pressure, indicating that the SAT affected the children's scores on both tests.

CONCLUSIONS AND RELEVANCE

SAT is influential in graphomotor assessment. The ZGT captures this trade-off by combining accuracy and speed measurements into one score that provides a realistic assessment of graphomotor skills. What This Article Adds: The newly developed ZGT provides occupational therapy practitioners with more precise information on graphomotor skills in children, adolescents, and young adults than currently available tools.

Effects of neuromuscular training on psychomotor development and active joint position sense in school children

As psychomotor development occurs in a specific social context, the environment in which a child is reared is important. The randomized study involved forty-five school children between 8 and 10 years. They were assigned to a control group (n = 23) and a neuromuscular training group (n = 22). A neuromuscular intervention for six weeks, on two nonconsecutive days, and in a circuit with 30-second stations was performed. The psychomotor development was evaluated through a psychomotor battery and the active joint position sense through the positional error. In the control group, the positional error decreased significantly in the shoulder (p < 0.001) and hip (p < 0.001), while the scores of motor function increased significantly which included balance (p < 0.001), spatio-temporal structuring (p = 0.022), global praxia (p = 0.002), and fine praxia (p = 0.003). In the neuromuscular training group, the positional error decreased significantly in the shoulder (p = 0.015), elbow (p = 0.015), wrist (p < 0.001), hip (p < 0.001), knee (p < 0.001), and ankle (p < 0.001), while the motor function scores increased significantly which included tonicity (p < 0.001), balance (p < 0.001), notion of the body (p < 0.001), spatio-temporal structuring (p < 0.001), global praxia (p < 0.001), and fine praxia (p < 0.001). A six-week neuromuscular training improved active joint position sense and psychomotor development in children.

Writing and Drawing Performance of School Age Children

The aim of our study was to investigate possible relationships between writing and drawing performance of school-aged children, in order to compare the two skills at the within-individual level. The sample consisted of 182 right- and left-handed children, aged 8 to 12 years. Children were examined by the Greek adaptation of the Luria-Nebraska neuropsychological battery in spontaneous writing, copying and writing to dictation and they were asked to complete four different drawing tasks. The results produced significant correlations between drawing scores and scores in all three writing tasks. Significant differences in drawing performance among proficient and poor hand writers were also found. On the other hand, there were no significant differences between right- and left-handers’ performance on the above tasks, despite the overrepresentation of left-handed amongst between poor writers. Our findings create a fruitful ground for the further study of early drawing as a means to predict later handwriting problems.

Characterization of fine motor development: dynamic analysis of children's drawing movements

In this study, we investigated children's fine motor development by analyzing drawing trajectories, kinematics and kinetics. Straight lines drawing task and circles drawing task were performed by using a force sensitive tablet. Forty right-handed and Chinese mother-tongue students aged 6-12, attending classes from grade 1 to 5, were engaged in the experiment. Three spatial parameters, namely cumulative trace length, vector length of straight line and vertical diameter of circle were determined. Drawing duration, mean drawing velocity, and number of peaks in stroke velocity profile (NPV) were derived as kinematic parameters. Besides mean normal force, two kinetic indices were proposed: normalized force angle regulation (NFR) and variation of fine motor control (VFC) for circles drawing task. The maturation and automation of fine motor ability were reflected by increased drawing velocity, reduced drawing duration, NPV and NFR, with decreased VFC in circles drawing task. Grade and task main effects as well as significant correlations between age and parameters suggest that factors such as schooling, age and task should be considered in the assessment of fine motor skills. Compared with kinematic parameters, findings of NFR and VFC revealed that kinetics is another important perspective in the analysis of fine motor movement.

A developmental study of the effect of music training on timed movements

When people clap to music, sing, play a musical instrument, or dance, they engage in temporal entrainment. We examined the effect of music training on the precision of temporal entrainment in 57 children aged 10–14 years (31 musicians, 26 non-musicians). Performance was examined for two tasks: self-paced finger tapping (discrete movements) and circle drawing (continuous movements). For each task, participants synchronized their movements with a steady pacing signal and then continued the movement at the same rate in the absence of the pacing signal. Analysis of movements during the continuation phase revealed that musicians were more accurate than non-musicians at finger tapping and, to a lesser extent, circle drawing. Performance on the finger-tapping task was positively associated with the number of years of formal music training, whereas performance on the circle-drawing task was positively associated with the age of participants. These results indicate that music training and maturation of the motor system reinforce distinct skills of timed movement.

The effects of shift work and time of day on fine motor control during handwriting

Handwriting is an elaborate and highly automatised skill relying on fine motor control. In laboratory conditions handwriting kinematics are modulated by the time of day. This study investigated handwriting kinematics in a rotational shift system and assessed whether similar time of day fluctuations at the work place can be observed. Handwriting performance was measured in two tasks of different levels of complexity in 34 shift workers across morning (6:00-14:00), evening (14:00-22:00) and night shifts (22:00-6:00). Participants were tested during all three shifts in 2-h intervals with mobile testing devices. We calculated average velocity, script size and writing frequency to quantify handwriting kinematics and fluency. Average velocity and script size were significantly affected by the shift work schedule with the worst performance during morning shifts and the best performance during evening shifts. Our data are of high economic relevance as fine motor skills are indispensable for accurate and effective production at the work place.

PRACTITIONER SUMMARY

Handwriting is one of the most complex fine motor skills in humans, which is frequently performed in daily life. In this study, we tested handwriting repeatedly at the work place in a rotational shift system. We found slower handwriting velocity and reduced script size during morning shifts.

Manual control age and sex differences in 4 to 11 year old children

To what degree does being male or female influence the development of manual skills in pre-pubescent children? This question is important because of the emphasis placed on developing important new manual skills during this period of a child's education (e.g. writing, drawing, using computers). We investigated age and sex-differences in the ability of 422 children to control a handheld stylus. A task battery deployed using tablet PC technology presented interactive visual targets on a computer screen whilst simultaneously recording participant's objective kinematic responses, via their interactions with the on-screen stimuli using the handheld stylus. The battery required children use the stylus to: (i) make a series of aiming movements, (ii) trace a series of abstract shapes and (iii) track a moving object. The tasks were not familiar to the children, allowing measurement of a general ability that might be meaningfully labelled ‘manual control’, whilst minimising culturally determined differences in experience (as much as possible). A reliable interaction between sex and age was found on the aiming task, with girls' movement times being faster than boys in younger age groups (e.g. 4–5 years) but with this pattern reversing in older children (10–11 years). The improved performance in older boys on the aiming task is consistent with prior evidence of a male advantage for gross-motor aiming tasks, which begins to emerge during adolescence. A small but reliable sex difference was found in tracing skill, with girls showing a slightly higher level of performance than boys irrespective of age. There were no reliable sex differences between boys and girls on the tracking task. Overall, the findings suggest that prepubescent girls are more likely to have superior manual control abilities for performing novel tasks. However, these small population differences do not suggest that the sexes require different educational support whilst developing their manual skills.

Changes in corticomotor excitability and inhibition after exercise are influenced by hand dominance and motor demand

Previous studies on handedness have often reported functional asymmetries in corticomotor excitability (CME) associated with voluntary movement. Recently, we have shown that the degree of post-exercise corticomotor depression (PED) and increase in short-interval cortical inhibition (SICI) after a repetitive finger movement task was less when the task was performed at a maximal voluntary rate (MVR) than when it was performed at a submaximal sustainable rate (SR). In the current study, we have compared the time course of PED and SICI in the dominant (DOM) and nondominant (NDOM) hands after an MVR and SR finger movement task to determine the influence of hand dominance and task demand. We tracked motor-evoked potential (MEP) amplitude from the first dorsal interosseous muscle of the DOM and NDOM hand for 20 min after a 10-s index finger flexion-extension task at MVR and SR. For all hand-task combinations, we report a period of PED and increased SICI lasting for up to 8 min. We find that the least demanding task, one that involved index finger movement of the DOM hand at SR, was associated with the greatest change in PED and SICI from baseline (63.6±5.7% and 79±2%, P<0.001, PED and SICI, respectively), whereas the most demanding task (MVR of the NDOM hand) was associated with the least change from baseline (PED: 88.1±3.6%, SICI: 103±2%; P<0.001). Our findings indicate that the changes in CME and inhibition associated with repetitive finger movement are influenced both by handedness and the degree of demand of the motor task and are inversely related to task demand, being smallest for an MVR task of the NDOM hand and greatest for an SR task of the DOM hand. The findings provide additional evidence for differences in neuronal processing between the dominant and nondominant hemispheres in motor control.

Exploring structural learning in handwriting

Structural learning suggests that the human nervous system learns general rules that can be applied when controlling actions involving similar structures (e.g. using a variety of bicycles when learning to ride). These general rules can then facilitate skill acquisition in novel but related situations (e.g. a new bicycle). We tested this concept by investigating whether learned asymmetries in handwriting (greater ease in moving the hand rightwards and downwards within Western-educated populations) are present in the non-preferred hand as predicted by structural learning. We found these asymmetries in both hands of a right-handed population when tracing abstract shapes. We then ruled out biomechanical explanations by finding the same results with a left-handed population. These findings provide support for structural learning and explain: (1) the rapidity with which individuals can learn to write with their non-preferred hand; (2) the presence of a higher abstract (effector independent) level within voluntary motor control organisation.

Electrocortical dynamics reflect age-related differences in movement kinematics among children and adults

Previous neuroimaging and behavioral studies demonstrated structural and functional changes in the motor system across childhood. However, it is unclear what functionally relevant electrocortical processes underlie developmental differences in motor planning and control during multijoint, goal-directed movements. The current study characterized age-related differences in electrocortical processes during the performance of discrete aiming movements in children and adults. Electroencephalography and movement kinematics were recorded from 3 groups of participants (n = 15 each): young children (mean 6.7 years), older children (mean 10.2 years), and adults (mean 22.1 years). Age-related differences were evident in the electroencephalographic (EEG) signals. First, young children exhibited less movement-related activity in task-relevant motor areas compared with adults (movement-related cortical potentials). Second, young children exhibited greater activation (less alpha power) of the frontal areas and less activation of the parietal areas as compared with the other groups. At the behavioral level, young children made slower and jerkier movements, with less consistent directional planning compared with older children and adults. Significant correlations were also found between EEG and movement kinematic measures. Taken together, the results of this study provide evidence that age-related differences in the quality of motor planning and performance are reflected in the differences in electrocortical dynamics among children and adults.

Ontogenesis of laterality in 3- to 10-yr.-old children: increased unimanual independence grounded on improved bimanual motor function

Underlying sensorimotor factors, such as intermanual coupling, contributing to optimal laterality, long remain immature. Using the handmotor laterality blackboard, developmental change in symmetric bimanual motor function for 413 children in groups of 3 to 10 years of age shows synchronicity increased between groups 3 and 5 years of age; but between groups 5 and 7 years of age, given immature coupling, one hand may still disturb the movements of the other one. Between groups 7 and 9 years of age, the hands gradually stop disturbing each other and move independently and fluently. Changes in intermanual coupling with increasing unimanual independence represent expression of changing interhemispheric integration across groups. This promotes optimal laterality and task distribution between the hands. Maturation of the corpus callosum is inferred to be a factor in these ontogenetic changes which ultimately lead to optimal left hemisphere specialization for actions such as fluent writing.

Categories of manual asymmetry and their variation with advancing age

Manual asymmetries were analyzed in 18- to 63-year-old right-handers in different motor tasks. This analysis aimed at describing the asymmetry profile for each task and assessing their stability across ages. For this purpose, performance of the right and left hands were analyzed in the following aspects: simple reaction time, rate of sequential finger movements, maximum grip force, accuracy in anticipatory timing, rate of repetitive tapping, and rate of drawing movements. In addition, stability of manual preference across ages was assessed through the Edinburgh inventory (Oldfield, 1971). The results indicated different profiles of manual asymmetry, with identification of three categories across tasks: symmetric performance (asymmetry indices close to zero), inconsistent asymmetry (asymmetry indices variable in magnitude and direction), and consistent asymmetry (asymmetry indices favoring a single hand). The different profiles observed in the young adults were stable across ages with two exceptions: decreased lateral asymmetry for maximum grip force and increased asymmetry for sequential drawing in older individuals. These results indicate that manual asymmetries are task specific. Such task specificity is interpreted to be the result of different sensorimotor requirements imposed by each motor task in association with motor experiences accumulated over the lifetime. Analysis of manual preference showed that strength of preference for the right hand was greater in older individuals.

Developmental differences in drawing performance of the dominant and non-dominant hand in right-handed boys and girls

This paper addresses the development of fine motor skills in the dominant and non-dominant hand. A total of 60 right-handed children, aged 4-12 years old, were divided in five groups of 12 children, with six girls and six boys in each group. The children were presented with drawing tasks that had to be performed with the dominant and non-dominant hand. Small or large targets had to be connected by lines making either a zigzag (discrete) or slalom (continuous) movement. For each task, effects of age group, gender, hand, and target size were examined for drawing time, percentage of stop time, drawing distance, velocity, and errors. Comparison of stop times in both tasks showed that the zigzag task was performed in a discrete way while the slalom task was performed more continuously, except in the youngest children, who performed both tasks in a discrete manner. With increasing age the children performed the tasks faster, more accurate and with shorter stops. No significant differences were found between boys and girls. While a shorter drawing distance and less errors were observed for the dominant hand in both tasks, drawing time and velocity were not significantly different between both hands. However, the percentage of stop time was higher for the dominant hand. Moving to smaller targets resulted in slower and less accurate performance. A significant interaction of age group and hand was found for errors in both tasks, and for stop time and velocity in the slalom task, suggesting differential maturational changes for both hands in discrete and continuous drawing tasks.

Bimanual interference in children performing a dual motor task

The present study addressed the development of bimanual interference in children performing a dual motor task, in which each hand executes a different task simultaneously. Forty right-handed children (aged 4, 5-6, 7-8 and 9-11years, ten in each age group) were asked to perform a bimanual task in which they had to tap with a pen using the non-preferred hand and simultaneously trace a circle or a square with a pen using the preferred hand as quickly as possible. Tapping and tracing were also performed unimanually. Differences between unimanual and bimanual performance were assessed for number of taps, length of tap trace and mean tracing velocity. It was assumed that with increasing age, better bimanual coordination would result in better performance on the dual task showing less intermanual interference. The results showed that tapping and tracing performance increased with age, unimanually as well as bimanually, consistent with developmental advancement. However, the percentage of intermanual interference due to bimanual performance was not significantly different in the four age groups. Although performing the dual task resulted in mutual intermanual interference, all groups showed a significant effect of tracing shape. More specifically, all age groups showed a larger percentage decrease in tracing velocity when performing the circle compared to the square in the dual task. The present study reveals that children as young as four years are able to coordinate both hands when tapping and tracing bimanually.

Acquisition of the lateral inconsistency in involuntary behaviour of upper limbs in 12-year-old children during walking at moderate speed

The aim of this work was to investigate possible lateralisation in the behaviour of periodic motion of the human upper limb, during normal walking at a comfortable speed of locomotion. Ten healthy pre-adolescent, strongly right-handed, 12-year-old males participated in the experiment. Participants were walking on a treadmill with a standardised velocity of 1.1m/s (comfortable speed for all of them). A video analysis system with Silicon software was used to synchronically measure various angles of arms and forearms. The initial, final and interim angular positions of both arms and forearms in 10 cycles of each participant were compared in terms of variations (cycle to cycle) between both upper extremities at corresponding phases of each cycle for distal and proximal segments, respectively. We compared the coefficients of variation in relation to the spatial and temporal data of both limbs and their angular velocities. In addition we investigated the level of cycle-to-cycle regularity (constancy) of behaviour in relation to various positions, periods and velocities of movement of upper extremities (specifically arms and forearms) using the Eta non-linear method of correlation. All participants exhibited a lower level of regularity for the distal segments. The spatial and temporal variations in the dominant limb were also greater than the non-dominant limb for all participants. This may be due to a larger contribution from the right-sided muscles that are considered to be the main contributing factor to the motion of the dominant upper limb during walking, rather than simply gravity force acting alone. A possible practical application of this information may be useful in the objective clinical identification of the level of dominance of the upper extremity (arm plus forearm), in addition to 'traditional' handedness.