Kinematic Assessment of Fine Motor Skills in Children: Comparison of a Kinematic Approach and a Standardized Test.

Deficits in fine motor skills have been reported in some children with neurodevelopmental disorders such as amblyopia or strabismus. Therefore, monitoring the development of motor skills and any potential improvement due to therapy is an important clinical goal. The aim of this study was to test the feasibility of performing a kinematic assessment within an optometric setting using inexpensive, portable, off-the-shelf equipment. The study also assessed whether kinematic data could enhance the information provided by a routine motor function screening test (the Movement Assessment Battery for Children, MABC). Using the MABC-2, upper limb dexterity was measured in a cohort of 47 typically developing children (7-15 years old), and the Leap motion capture system was used to record hand kinematics while children performed a bead-threading task. Two children with a history of amblyopia were also tested to explore the utility of a kinematic assessment in a clinical population. For the typically developing children, visual acuity and stereoacuity were within the normal range; however, the average standardized MABC-2 scores were lower than published norms. Comparing MABC-2 and kinematic measures in the two children with amblyopia revealed that both assessments provide convergent results and revealed deficits in fine motor control. In conclusion, kinematic assessment can augment standardized tests of fine motor skills in an optometric setting and may be useful for measuring visuomotor function and monitoring treatment outcomes in children with binocular vision anomalies.

The effects of task difficulty on gaze behaviour during landing with visual flight rules in low-time pilots.

Eye movements have been used to examine the cognitive function of pilots and understand how information processing abilities impact performance. Traditional and advanced measures of gaze behaviour effectively reflect changes in cognitive load, situational awareness, and expert-novice differences. However, the extent to which gaze behaviour changes during the early stages of skill development has yet to be addressed. The current study investigated the impact of task difficulty on gaze behaviour in low-time pilots (N=18) while they completed simulated landing scenarios. An increase in task difficulty resulted in longer fixation of the runway, and a reduction in the stationary gaze entropy (gaze dispersion) and gaze transition entropy (sequence complexity). These findings suggest that pilots' gaze became less complex and more focused on fewer areas of interest when task difficulty increased. Additionally, a novel approach to identify and track instances when pilots restrict their attention outside the cockpit (i.e., gaze tunneling) was explored and shown to be sensitive to changes in task difficulty. Altogether, the gaze-related metrics used in the present study provide valuable information for assessing pilots gaze behaviour and help further understand how gaze contributes to better performance in low-time pilots.

Investigation of Camera-Free Eye-Tracking Glasses Compared to a Video-Based System.

Technological advances in eye-tracking have resulted in lightweight, portable solutions that are capable of capturing eye movements beyond laboratory settings. Eye-tracking devices have typically relied on heavier, video-based systems to detect pupil and corneal reflections. Advances in mobile eye-tracking technology could facilitate research and its application in ecological settings; more traditional laboratory research methods are able to be modified and transferred to real-world scenarios. One recent technology, the AdHawk MindLink, introduced a novel camera-free system embedded in typical eyeglass frames. This paper evaluates the AdHawk MindLink by comparing the eye-tracking recordings with a research "gold standard", the EyeLink II. By concurrently capturing data from both eyes, we compare the capability of each eye tracker to quantify metrics from fixation, saccade, and smooth pursuit tasks-typical elements in eye movement research-across a sample of 13 adults. The MindLink system was capable of capturing fixation stability within a radius of less than 0.5∘, estimating horizontal saccade amplitudes with an accuracy of 0.04∘± 2.3∘, vertical saccade amplitudes with an accuracy of 0.32∘± 2.3∘, and smooth pursuit speeds with an accuracy of 0.5 to 3∘s, depending on the pursuit speed. While the performance of the MindLink system in measuring fixation stability, saccade amplitude, and smooth pursuit eye movements were slightly inferior to the video-based system, MindLink provides sufficient gaze-tracking capabilities for dynamic settings and experiments.

Path Configuration Complexity Affects Spatial Memory Span on the eCorsi Task but Does Not Influence Performance of a Concurrent Auditory Discrimination Task.

Visuospatial working memory is often assessed using the Corsi block-tapping task where set size is used to estimate capacity. It is well established that characteristics of the Corsi task path configuration such as length, crossings, and angles influence recall accuracy suggesting that more complex path configurations increase the load on working memory. However, the interaction between set size and path configuration is not well understood. Here we used a secondary auditory task to probe if set size and path configuration impose a similar type of load on the system. Nineteen participants (age = 25.3 ± 3.9 years) performed a computerized version of the Corsi test either alone (single) or simultaneously with an auditory tone discrimination task (dual). The eCorsi task involved a set of simple (no crosses, shorter lengths, larger angles) or complex (>2 crosses, longer lengths, smaller angles) paths at set sizes of five to eight blocks. Results showed significantly lower recall accuracy for the complex compared to the simple paths (63.32% vs. 86.38%, p < 0.001) at all set sizes, regardless of task condition (single, dual). Auditory performance (accuracy and response time) was significantly lower in the dual compared to single task (85.34% vs. 99.67%, p < 0.001), but performance was not affected by the complexity of the eCorsi path configuration. These findings suggest that set size and path complexity impose a different type of load on the working memory system and may rely on different resources.

The role of binocular vision in the control and development of visually guided upper limb movements.

Vision provides a key sensory input for the performance of fine motor skills, which are fundamentally important to daily life activities, as well as skilled occupational and recreational performance. Binocular visual function is a crucial aspect of vision that requires the ability to combine inputs from both eyes into a unified percept. Summation and fusion are two aspects of binocular processing associated with performance advantages, including more efficient visuomotor control of upper limb movements. This paper uses the multiple processes model of limb control to explore how binocular viewing could facilitate the planning and execution of prehension movements in adults and typically developing children. Insight into the contribution of binocularity to visuomotor control also comes from examining motor performance in individuals with amblyopia, a condition characterized by reduced visual acuity and poor binocular function. Overall, research in this field has advanced our understanding of the role of binocular vision in the development and performance of visuomotor skills, the first step towards developing assessment tools and targeted rehabilitation for children with neurodevelopment disorders at risk of poor visuomotor outcomes. This article is part of a discussion meeting issue 'New approaches to 3D vision'.

Temporal Eye-Hand Coordination During Visually Guided Reaching in 7- to 12-Year-Old Children With Strabismus.

Purpose: We recently found slow visually guided reaching in strabismic children, especially in the final approach. Here, we expand on those data by reporting saccade kinematics and temporal eye-hand coordination during visually guided reaching in children treated for strabismus compared with controls. Methods: Thirty children diagnosed with esotropia, a form of strabismus, 7 to 12 years of age and 32 age-similar control children were enrolled. Eye movements and index finger movements were recorded. While viewing binocularly, children reached out and touched a small dot that appeared randomly in one of four locations along the horizontal meridian (±5° or ±10°). Saccade kinematic measures (latency, accuracy and precision, peak velocity, and frequency of corrective and reach-related saccades) and temporal eye-hand coordination measures (saccade-to-reach planning interval, saccade-to-reach peak velocity interval) were compared. Factors associated with impaired performance were also evaluated. Results: During visually guided reaching, strabismic children had longer primary saccade latency (strabismic, 195 ± 29 ms vs. control; 175 ± 23 ms; P = 0.004), a 25% decrease in primary saccade precision (0.15 ± 0.06 vs. 0.12 ± 0.03; P = 0.007), a 45% decrease in the final saccade precision (0.16 ± 0.06 vs. 0.11 ± 0.03; P < 0.001), and more reach-related saccades (16 ± 13% of trials vs. 8 ± 6% of trials; P = 0.001) compared with a control group. No measurable stereoacuity was related to poor saccade kinematics. Conclusions: Strabismus impacts saccade kinematics during visually guided reaching in children, with poor binocularity playing a role in performance. Coupled with previous data showing slow reaching in the final approach, the current saccade data suggest that children treated for strabismus have not yet adapted or formed an efficient compensatory strategy during visually guided reaching.

EEG reveals deficits in sensory gating and cognitive processing in asymptomatic adults with a history of concussion.

OBJECTIVE: Individuals with a concussion history tend to perform worse on dual-tasks compared controls but the underlying neural mechanisms contributing to these deficits are not understood. This study used event-related potentials (ERPs) to investigate sensory gating and cognitive processing in athletes with and without a history of concussion while they performed a challenging dual-task. METHODS: We recorded sensory (P50, N100) and cognitive (P300) ERPs in 30 athletes (18 no previous concussion; 12 history of concussion) while they simultaneously performed an auditory oddball task and a working memory task that progressively increased in difficulty. RESULTS: The concussion group had reduced auditory performance as workload increased compared to the no-concussion group. Sensory gating and cognitive processing were reduced in the concussion group indicating problems with filtering relevant from irrelevant information and appropriately allocating resources. Sensory gating (N100) was positively correlated with cognitive processing (P300) at the hardest workload in the no-concussion group but negatively correlated in the concussion group. CONCLUSION: Concussions result in long-term problems in behavioral performance, which may be due to poorer sensory gating that impacts cognitive processing. SIGNIFICANCE: Problems effectively gating sensory information may influence the availability or allocation of attention at the cognitive stage in those with a concussion.

Binocular Viewing Facilitates Size Constancy for Grasping and Manual Estimation.

A prerequisite for efficient prehension is the ability to estimate an object's distance and size. While most studies demonstrate that binocular viewing is associated with a more efficient grasp programming and execution compared to monocular viewing, the factors contributing to this advantage are not fully understood. Here, we examined how binocular vision facilitates grasp scaling using two tasks: prehension and manual size estimation. Participants (n = 30) were asked to either reach and grasp an object or to provide an estimate of an object's size using their thumb and index finger. The objects were cylinders with a diameter of 0.5, 1.0, or 1.5 cm placed at three distances along the midline (40, 42, or 44 cm). Results from a linear regression analysis relating grip aperture to object size revealed that grip scaling during monocular viewing was reduced similarly for both grasping and estimation tasks. Additional analysis revealed that participants adopted a larger safety margin for grasping during monocular compared to binocular viewing, suggesting that monocular depth cues do not provide sufficient information about an object's properties, which consequently leads to a less efficient grasp execution.

Gaze behaviour: A window into distinct cognitive processes revealed by the Tower of London test.

The analysis of gaze behaviour during complex tasks provides a promising non-invasive method to examine how specific eye movement patterns relate to various aspects of cognition and action. Notably, the association between aspects of gaze behaviour and subsequent goal-directed action during high-level visuospatial problem solving remains elusive. Therefore, the current study comprehensively examined gaze behaviour using traditional and entropy-based gaze analyses in healthy adults (N = 27) while they performed the Freiburg version of the Tower of London task. Results demonstrated that both gaze analyses provided crucial temporal and spatial information related to planning, solution elaboration and execution. Specifically, gaze biases toward task-relevant areas (i.e., the work space) and an increase in gaze complexity (i.e., gaze transition entropy) during optimal performance reflected changes in cognitive demands as task difficulty increased. A comparison between optimal and non-optimal performance revealed sub-optimal gaze patterns that occurred in the early stages of planning, which were taken to reflect poor information extraction from the task environment and impaired maintenance of information in visuospatial working memory. Gaze behaviour during movement execution indicated an increased need to extract and process information from the goal space. Consequently, movement execution time increased in order to reverse erroneous movements and re-sequence the problem solution. Taken together, the traditional and entropy-based gaze analyses applied in the present study provide a promising approach to identify eye movement patterns that support neurocognitive performance on tasks relying on visuospatial planning and problem solving.

Evaluating visuomotor coordination in children with amblyopia.

Past research has reported deficits on reaching and grasping tasks in adults with amblyopia and degraded stereoacuity, but less is known about visuomotor deficits in children-specifically, for complex tasks that require movement sequencing. This study therefore compared the visuomotor performance in 21 children with abnormal binocular vision (patient group) due to amblyopia and/or strabismus to that of 236 children with normal binocular vision development (control group) ages 5-14 years. Visual acuity, stereoacuity, and hand-movement kinematics on a bead-threading task were assessed. The patient group showed significantly longer durations than the control group on grasp, thread, and total movement durations. Both groups of participants were then split into immature (ages 5-9 years) and mature (ages 10-14 years) groups based on the maturation age for these parameters in control children. Grasp duration was longer in both mature and immature patient groups; thread and total movement durations were longer in the mature patient group only. Grasp duration was the most disrupted kinematic parameter in children with disrupted binocular vision due to amblyopia and/or strabismus, regardless of age. The level of stereoacuity loss rather than the depth of visual acuity loss was associated with the severity of visuomotor deficits.

Reach Kinematics During Binocular Viewing in 7- to 12-Year-Old Children With Strabismus.

Purpose: Eye-hand coordination is essential for normal development and learning. Discordant binocular experience from childhood strabismus results in sensory and ocular motor impairments that can affect eye-hand coordination. We assessed reach kinematics during visually guided reaching in children treated for strabismus compared with controls. Methods: Thirty-six children aged 7 to 12 years diagnosed with esotropia, a form of strabismus, and a group of 35 age-similar control children were enrolled. Reach movements during visually guided reaching were recorded using the LEAP Motion Controller. While viewing binocularly, children reached out and touched a small dot that appeared randomly in one of four locations (±5° or ±10°). Kinematic measures were reach reaction time, total reach duration, peak velocity, acceleration duration, and deceleration duration. Touch accuracy and factors associated with impaired reach kinematics were evaluated. Results: Strabismic children had longer total reach duration (545 ± 60 ms vs. 504 ± 43 ms; P = 0.002), had longer deceleration duration (343 ± 54 ms vs. 312 ± 45 ms; P = 0.010), and were less accurate (93% ± 6% vs. 96% ± 5%, P = 0.007) than controls. No differences were found for reach reaction time, peak velocity, or acceleration duration (all Ps ≥ 0.197). Binocular dysfunction was more related to slow reaching than amblyopic eye visual acuity. Conclusions: Strabismus affects visually guided reaching in children, with slower reaching in the final approach and reduced endpoint accuracy. Binocular dysfunction was predictive of slow reaching. Unlike strabismic adults who show longer acceleration duration, longer deceleration in the final approach in strabismic children indicates a difference in control that could be due to reduced ability to use visual feedback.

Development of eye-hand coordination in typically developing children and adolescents assessed using a reach-to-grasp sequencing task.

Eye-hand coordination is required to accurately perform daily activities that involve reaching, grasping and manipulating objects. Studies using aiming, grasping or sequencing tasks have shown a stereotypical temporal coupling pattern where the eyes are directed to the object in advance of the hand movement, which may facilitate the planning and execution required for reaching. While the temporal coordination between the ocular and manual systems has been extensively investigated in adults, relatively little is known about the typical development of eye-hand coordination. Therefore, the current study addressed an important knowledge gap by characterizing the profile of eye-hand coupling in typically developing school-age children (n = 57) and in a cohort of adults (n = 30). Eye and hand movements were recorded concurrently during the performance of a bead threading task which consists of four distinct movements: reach to bead, grasp, reach to needle, and thread. Results showed a moderate to high correlation between eye and hand latencies in children and adults, supporting that both movements were planned in parallel. Eye and reach latencies, latency differences, and dwell time during grasping and threading, showed significant age-related differences, suggesting eye-hand coupling becomes more efficient in adolescence. Furthermore, visual acuity, stereoacuity and accommodative facility were also found to be associated with the efficiency of eye-hand coordination in children. Results from this study can serve as reference values when examining eye and hand movement during the performance of fine motor skills in children with neurodevelopmental disorders.

Pupillometry provides a psychophysiological index of arousal level and cognitive effort during the performance of a visual-auditory dual-task in individuals with a history of concussion.

Research shows that concussions cause long-term deficits in executive functions when tested using challenging tasks with high cognitive load. The neurophysiological mechanism(s) associated with executive dysfunction are not well understood. Pupillometry provides a non-invasive index of arousal and cognitive load; therefore, the current study investigated whether pupillometry could help explain the persistent deficits in dual-task performance in individuals with a history of concussion (n = 14) compared to controls (n = 13). Participants were tested using a computerized Corsi block task which increased in difficulty as a function of set size (i.e., number of blocks to be remembered) and task condition (i.e., performed alone and concurrently with an auditory task). Pupil size was measured during the initial fixation prior to the Corsi task to assess arousal level, and during the encoding phase to assess task evoked pupil response. Results showed that: 1) in contrast to the control group, pupil size was not modulated by task condition in the concussed group indicating that arousal level was similar in the single and dual task; 2) task evoked pupil dilation increased as a function of set size in the single task in both groups, 3) in contrast to the control group, those with a history of concussion had similar pupil size during the single and dual task conditions. One interpretation of these results is that individuals with a history of concussion exert greater effort when performing relatively easier tasks, and they reach capacity limits when the cognitive load is lower in comparison to non-concussed individuals. In conclusion, pupillometry may provide insight into persisting deficits in executive functions following concussion(s).

Stereopsis contributes to the predictive control of grip forces during prehension.

Binocular viewing is associated with a superior prehensile performance, which is particularly evident in the latter part of the reach as the hand approaches and makes contact with the target object. However, the visuomotor mechanisms through which binocular vision serves prehension are not fully understood. This study assessed the role of stereopsis in the predictive control of grasping by measuring grip force. Twenty participants performed a precision reach-to-grasp task in four viewing conditions: binocular, monocular, and with reduced stereoacuity (200 arc sec, > 400 arc sec). Monocular, compared to binocular viewing, was associated with a fourfold increase in grasp errors, a 56% increase in grasp duration, 22% decrease in grip force at 50 ms following grasp initiation, and the time of peak force occurred 40% later after grasp initiation (all p < 0.05). Grasp performance was also disrupted when viewing with reduced stereoacuity. Notably, grip force at the time of object lift-off was comparable between all viewing conditions. These results demonstrate that binocular stereopsis contributes to the efficient programming of grip forces. Specifically, stereopsis may provide important sensory information that enables the central nervous system to engage in predictive control of grasping.

Test-retest repeatability reveals a temporal kinematic signature for an upper limb precision grasping task in adults.

Hand-eye coordination skills, such as reaching and grasping, are fundamentally important for the performance of most daily activities. Upper limb kinematics recorded by motion tracking systems provide detailed insight into the central nervous system control of movement planning and execution. For example, kinematic metrics can reveal deficits in control, and compensatory neuromotor strategies in individuals with neuropathologies. However, the clinical utility of kinematic metrics is currently limited because their psychometric properties, such as test-retest repeatability, have not been well characterized. Therefore, the purpose of this study was to examine the degree of repeatability of spatiotemporal kinematic metrics and determine which, if any, measures form a kinematic signature for a precision grasping task. Healthy adults (n = 40) were tested on two occasions separated by 5-10 days on a bead threading task consisting of reaching and precision grasping. Results showed good test-retest repeatability for reach peak velocity, reach and grasp durations, whereas poor to moderate reliability was observed for measures of spatial precision and maximum grip aperture. In addition, analysis showed that reliable estimates of kinematic metrics can be obtained using 10 trials. Overall, our results indicate that reach peak velocity and temporal metrics form a stable characteristic, or a kinematic signature, of individual performance on a standardized bead threading task. These findings suggest potential utility in applying kinematic metrics for clinical assessment of upper limb reaching tasks.

Effects of blocked vs. interleaved administration mode on saccade preparatory set revealed using pupillometry.

Eye movements have been used extensively to assess information processing and cognitive function. However, significant variability in saccade performance has been observed, which could arise from methodological variations across different studies. For example, prosaccades and antisaccades have been studied using either a blocked or interleaved design, which has a significant influence on error rates and latency. This is problematic as it makes it difficult to compare saccade performance across studies and may limit the ability to use saccades as a behavioural assay to assess neurocognitive function. Thus, the current study examined how administration mode influences saccade related preparatory activity by employing pupil size as a non-invasive proxy for neural activity related to saccade planning and execution. Saccade performance and pupil dynamics were examined in eleven participants as they completed pro- and antisaccades in blocked and interleaved paradigms. Results showed that administration mode significantly modulated saccade performance and preparatory activity. Reaction times were longer for both pro- and antisaccades in the interleaved condition, compared to the blocked condition (p < 0.05). Prosaccade pupil dilations were larger in the interleaved condition (p < 0.05), while antisaccade pupil dilations did not significantly differ between administration modes. Additionally, ROC analysis provided preliminary evidence that pupil size can effectively predict saccade directional errors prior to saccade onset. We propose that task-evoked pupil dilations reflect an increase in preparatory activity for prosaccades and the corresponding cognitive demands associated with interleaved administration mode. Overall, the results highlight the importance that administration mode plays in the design of neurocognitive tasks.

Age-Related Deficits in Binocular Vision Are Associated With Poorer Inhibitory Control in Healthy Older Adults.

A robust association between reduced visual acuity and cognitive function in older adults has been revealed in large population studies. The aim of this work was to assess the relation between stereoacuity, a key aspect of binocular vision, and inhibitory control, an important component of executive functions. Inhibition was tested using the antisaccade task in older adults with normal or reduced stereopsis (study 1), and in young adults with transiently reduced stereopsis (study 2). Older adults with reduced stereopsis made significantly more errors on the antisaccade task in comparison to those with normal stereopsis. Specifically, there was a significant correlation between stereoacuity and antisaccade errors (r = 0.27, p = 0.019). In contrast, there were no significant differences in antisaccade errors between the normal and reduced stereopsis conditions in the young group. Altogether, results suggest that the association between poorer stereopsis and lower inhibitory control in older adults might arise due to central nervous system impairment that affects the processing of binocular disparity and antisaccades. These results add to a growing body of literature, which highlights the interdependence of sensory and cognitive decline in older adults.

Contribution of stereopsis, vergence, and accommodative function to the performance of a precision grasping and placement task in typically developing children age 8-14 years.

Upper limb reaching and grasping movements are performed more efficiently during binocular viewing; however, the distinct contribution of stereopsis, fusional vergence, and accommodation (binocular facility, amplitude and accuracy) has not been examined in typically developing children. This study examined binocular visual function in a cohort of 57 typically developing children, 8 to 14 years old. Hand kinematics were recorded using a motion capture camera while children performed a prehension task involving threading a bead onto a needle. Results showed that different aspects of binocular vision contribute to the control of distinct phases of upper limb movements. Specifically, fusional vergence was associated with higher peak reach velocity, stereoacuity was associated with shorter grasp execution, and accommodation was associated with shorter placement duration. These findings suggest that different aspects of binocular vision play an important role in optimizing the control of distinct phases of prehension movements during development.

A History of Concussion Affects Relevancy-Based Modulation of Cortical Responses to Tactile Stimuli.

Modulating cortical excitability based on a stimulus' relevance to the task at hand is a component of sensory gating, and serves to protect higher cortical centers from being overwhelmed with irrelevant information (McIlroy et al., 2003; Kumar et al., 2005; Wasaka et al., 2005). This study examined relevancy-based modulation of cortical excitability, and corresponding behavioral responses, in the face of distracting stimuli in participants with and without a history of concussion (mean age 22 ± 3 SD years; most recent concussion 39.1 ± 30 SD months). Participants were required to make a scaled motor response to the amplitudes of visual and tactile stimuli presented individually or concurrently. Task relevance was manipulated, and stimuli were occasionally presented with irrelevant distractors. Electroencephalography (EEG) and task accuracy data were collected from participants with and without a history of concussion. The somatosensory-evoked N70 event-related potential (ERP) was significantly modulated by task relevance in the control group but not in those with a history of concussion, and there was a significantly greater cost to task accuracy in the concussion history group when relevant stimuli were presented with an irrelevant distractor. This study demonstrated that relevancy-based modulation of electrophysiological responses and behavioral correlates of sensory gating differ in people with and without a history of concussion, even after patients were symptom-free and considered recovered from their injuries.

Concurrent maturation of visuomotor skills and motion perception in typically-developing children and adolescents.

Perceptual and visuomotor skills undergo considerable development from early childhood into adolescence; however, the concurrent maturation of these skills has not yet been examined. This study assessed visuomotor function and motion perception in a cross-section of 226 typically-developing children between 4 and 16 years of age. Participants were tested on three tasks hypothesized to engage the dorsal visual stream: threading a bead on a needle, marking dots using a pen, and discriminating form defined by motion contrast. Mature performance was reached between 8 and 12 years, with youngest maturation for kinematic measures for a reach-to-grasp task, and oldest maturation for a precision tapping task. Performance on the motion perception task shared no association with motor skills after controlling for age.