Predicting motor behavior: an efficient EEG signal processing pipeline to detect brain states with potential therapeutic relevance for VR-based neurorehabilitation.

Virtual reality (VR)-based motor therapy is an emerging approach in neurorehabilitation. The combination of VR with electroencephalography (EEG) presents further opportunities to improve therapeutic efficacy by personalizing the paradigm. Specifically, the idea is to synchronize the choice and timing of stimuli in the perceived virtual world with fluctuating brain states relevant to motor behavior. Here, we present an open source EEG single-trial based classification pipeline that is designed to identify ongoing brain states predictive of the planning and execution of movements. 9 healthy volunteers each performed 1080 trials of a repetitive reaching task with an implicit two-alternative forced choice, i.e., use of the right or left hand, in response to the appearance of a visual target. The performance of the EEG decoding pipeline was assessed with respect to classification accuracy of right vs. left arm use, based on the EEG signal at the time of the stimulus. Different features, feature extraction methods, and classifiers were compared at different time windows; the number and location of informative EEG channels and the number of calibration trials needed were also quantified, as well as any benefits from individual-level optimization of pipeline parameters. This resulted in a set of recommended parameters that achieved an average 83.3% correct prediction on never-before-seen testing data, and a state-of-the-art 77.1% in a real-time simulation. Neurophysiological plausibility of the resulting classifiers was assessed by time-frequency and event-related potential analyses, as well as by Independent Component Analysis topographies and cortical source localization. We expect that this pipeline will facilitate the identification of relevant brain states as prospective therapeutic targets in closed-loop EEG-VR motor neurorehabilitation.

Reaction time asymmetries provide insight into mechanisms underlying dominant and non-dominant hand selection.

Handedness is often thought of as a hand "preference" for specific tasks or components of bimanual tasks. Nevertheless, hand selection decisions depend on many factors beyond hand dominance. While these decisions are likely influenced by which hand might show performance advantages for the particular task and conditions, there also appears to be a bias toward the dominant hand, regardless of performance advantage. This study examined the impact of hand selection decisions and workspace location on reaction time and movement quality. Twenty-six neurologically intact participants performed targeted reaching across the horizontal workspace in a 2D virtual reality environment, and we compared reaction time across two groups: those selecting which hand to use on a trial-by-trial basis (termed the choice group) and those performing the task with a preassigned hand (the no-choice group). Along with reaction time, we also compared reach performance for each group across two ipsilateral workspaces: medial and lateral. We observed a significant difference in reaction time between the hands in the choice group, regardless of workspace. In contrast, both hands showed shorter but similar reaction times and differences between the lateral and medial workspaces in the no-choice group. We conclude that the shorter reaction times of the dominant hand under choice conditions may be due to dominant hand bias in the selection process that is not dependent upon interlimb performance differences.

Hand preference for unimanual and bimanual tasks: Evidence from questionnaires and preferential reaching.

The current research compared hand selection in a preferential reaching paradigm with unimanual (i.e., pick-up cup) and bimanual (pick-up cup and pour from pitcher) tasks. In addition, relationships between self-report, questionnaire-based hand preference (unimanual and bimanual) and patterns of hand selection were assessed. Data offer support for a division of labour between the hands in at the midline; however, bimanual selection otherwise reflects consideration of object proximity (i.e., location) and comfort (i.e., biomechanical constraints). When grasping cups in right space, the right-hand was used to stabilize the cup and left-hand to mobilize the pitcher, whereas the opposite pattern was observed in left-space. Unimanual hand selection was also driven by object location. Subsequent analyses revealed a relationship between unimanual measures, but not bimanual measures of hand preference. Overall, findings support the notion that questionnaire data are associated with hand preference for grasping to a certain extent; however, use of a comprehensive battery of assessments is recommended when assessing and/or predicting handedness.

The neural basis of hand choice: An fMRI investigation of the Posterior Parietal Interhemispheric Competition model.

The current study investigates a new neurobiological model of human hand choice: The Posterior Parietal Interhemispheric Competition (PPIC) model. The model specifies that neural populations in bilateral posterior intraparietal and superior parietal cortex (pIP-SPC) encode actions in hand-specific terms, and compete for selection across and within hemispheres. Actions with both hands are encoded bilaterally, but the contralateral hand is overrepresented. We use a novel fMRI paradigm to test the PPIC model. Participants reach to visible targets while in the scanner, and conditions involving free choice of which hand to use (Choice) are compared with when hand-use is instructed. Consistent with the PPIC model, bilateral pIP-SPC is preferentially responsive for the Choice condition, and for actions made with the contralateral hand. In the right pIP-SPC, these effects include anterior intraparietal and superior parieto-occipital cortex. Left dorsal premotor cortex, and an area in the right lateral occipitotemporal cortex show the same response pattern, while the left inferior parietal lobule is preferentially responsive for the Choice condition and when using the ipsilateral hand. Behaviourally, hand choice is biased by target location - for targets near the left/right edges of the display, the hand in ipsilateral hemispace is favoured. Moreover, consistent with a competitive process, response times are prolonged for choices to more ambiguous targets, where hand choice is relatively unbiased, and fMRI responses in bilateral pIP-SPC parallel this pattern. Our data provide support for the PPIC model, and reveal a selective network of brain areas involved in free hand choice, including bilateral posterior parietal cortex, left-lateralized inferior parietal and dorsal premotor cortices, and the right lateral occipitotemporal cortex.

Cognitive-perceptual load modulates hand selection in left-handers to a greater extent than in right-handers.

Previous studies have proposed that selecting which hand to use for a reaching task appears to be modulated by a factor described as "task difficulty," defined by either the requirement for spatial precision or movement sequences. However, we previously reported that analysis of the movement costs associated with even simple movements plays a major role in hand selection. We further demonstrated, in right-handers, that cognitive-perceptual loading modulates hand selection by interfering with the analysis of such costs. It has been reported that left-handers tend to show less dominant hand bias in selecting which hand to use during reaching. We, therefore, hypothesized that hand selection would be less affected by cognitive-perceptual loading in left-handers than in right-handers. We employed a visual search task that presented different levels of difficulty (cognitive-perceptual load), as established in previous studies. Our findings indicate that left-handed participants tend to show greater modulation of hand selection by cognitive-perceptual loading than right-handers. Left-handers showed lower dominant hand reaction times than right-handers, and greater high-cost movements that reached to extremes of the contralateral workspace under the most difficult task conditions. We previously showed in this task that midline crossing has high-energy and time costs and that they occur more frequently under cognitively demanding conditions. The current study revealed that midline crossing was associated with the lowest reaction times, in both handedness groups. The fact that left-handers showed lower dominant hand reaction times, and a greater number of high-cost cross-midline reaches under the most cognitively demanding conditions suggests that these actions were erroneous.

Hand Selection in Dribbling Phases: An Analysis of Non-Dominant Hand Usage and Dribble Change in Basketball.

This study investigates the influence of different dribbling phases on hand selection among basketball players across various categories. A total of 33 guard players, including 11 from high school, college, and NBA teams each, were observed. Video data analysis was utilized to determine the frequency of players using their dominant hands (DHs) and non-dominant hands (NDHs) during in-game dribbling phases. The dribbling phases were classified into three categories: First (the initiation of the dribble), Middle (during the dribble but not in First and Last), and Last (the completion of the dribble). Percentage, means, and standard deviations were computed for each category within the First, Middle, and Last measurements. A two-factor analysis of variance (ANOVA) was conducted, considering player category and dribbling phase as factors. The ANOVA revealed significant main effects of player category (p < 0.01) and dribbling phase (p < 0.01). Post hoc multiple comparisons using Holm's method indicated that, in the First phase, players exhibited a 6.5% higher preference for using their NDHs (43.4 ± 11.9%) compared to the Middle phase (36.9 ± 13.9%) (p < 0.05). Similarly, in the Last phase, players displayed a 5.3% greater inclination towards using their NDHs (42.2 ± 11.7%) compared to the Middle phase (p < 0.05). These findings provide quantitative evidence that the specific dribbling phase influences hand selection during gameplay. The implications of these results are significant for basketball coaches, as they can design targeted training programs and drills that simulate game scenarios and encourage NDH usage. By understanding the factors influencing hand choice, players can enhance their versatility and adaptability on the court. Furthermore, these findings contribute to player performance, skill development, and strategic decision making in dribbling phases.

Preferential Reaching and End-State Comfort: How Task Demands Influence Motor Planning.

Various factors (e.g., hand preference, object properties) constrain reach-to-grasp in hemispace. With object use, end-state comfort (ESC) has been shown to supersede the preferential use of one hand at the midline. To assess how location, size, and orientation of objects (dowel, mallet, cup) influence preferred-hand use and ESC (N = 50; Mage = 20.83), three preferential reaching tasks were implemented. Object location influenced hand selection in all tasks, along with size (cups) and orientation (mallets). Object location and orientation influenced ESC, but only with dowels and mallets. When oriented away from the preferred hand in hemispace, there was a higher occurrence of non-preferred hand use to facilitate ESC. Overall, findings add to understanding of ESC and preferential reaching with varying task demands.

The role of left fronto-parietal tracts in hand selection: Evidence from neurosurgery.

Strong right-hand preference on the population level is a uniquely human feature, although its neural basis is still not clearly defined. Recent behavioural and neuroimaging literature suggests that hand preference may be related to the orchestrated function and size of fronto-parietal white matter tracts bilaterally. Lesions to these tracts induced during tumour resection may provide an opportunity to test this hypothesis. In the present study, a cohort of seventeen neurosurgical patients with left hemisphere brain tumours were recruited to investigate whether resection of certain white matter tracts affects the choice of hand selected for the execution of a goal-directed task (assembly of jigsaw puzzles). Patients performed the puzzles, but also tests for basic motor ability, selective attention and visuo-constructional ability, preoperatively and one month after surgery. An atlas-based disconnectome analysis was conducted to evaluate whether resection of tracts was significantly associated with changes in hand selection. Diffusion tractography was also used to dissect fronto-parietal tracts (the superior longitudinal fasciculus) and the corticospinal tract. Results showed a shift in hand selection despite the absence of any motor or cognitive deficits, which was significantly associated with frontal and parietal resections rather than other lobes. In particular, the shift in hand selection was significantly associated with the resection of dorsal rather than ventral fronto-parietal white matter connections. Dorsal white matter pathways contribute bilaterally to control of goal-directed hand movements. We show that unilateral lesions, that may unbalance the cooperation of the two hemispheres, can alter the choice of hand selected to accomplish movements.

Investigating the Efficacy of the Hand Selection Complexity Task Across the Lifespan.

There is inconsistent evidence demonstrating a relationship between task complexity and hand preference. However, analyzing the point at which task complexity overrides the decision to demonstrate a biomechanically efficient movement can enable complexity to be quantified. Young children (ages 3-7), adolescents (ages 8-12), young adults (ages 18-25), and older adults (ages 65+) performed a newly developed Hand Selection Complexity Task (HSCT) and completed the Waterloo Handedness Questionnaire (WHQ). The HSCT included a reciprocal Fitts' tapping task performed in the contralateral space (i.e., same side as preferred hand), followed by ipsilateral space (i.e., opposite side of preferred hand). An alternating contralateral-ipsilateral pattern enabled the participant to progress through six levels of difficulty in three conditions (manipulating target amplitude, width, and combined factors). As participants were free to perform with whichever hand (i.e., preferred, non-preferred) they deemed most appropriate, the level of difficulty where a hand switch occurred was identified. HSCT completion time and error scores were also computed. Findings revealed age to be a significant predictor of dependent measures when considering significant effects and interactions. Combined with the covariate WHQ score as a significant predictor of HSCT time and errors (in some, but not all cases), it can be argued that age-related effects reflect the development of handedness, and changes in strength of handedness across the lifespan. Together, findings suggest that task complexity plays an important role in hand selection when performing a task of increasing difficulty. It appears that task complexity will take precedent over object proximity and biomechanical efficiency, at a certain point, in order to complete the movement with the preferred hand. This point ultimately changes throughout the lifespan.

Hand selection in a preferential reaching task: The effects of object location, orientation, and task intention in preadolescent children.

INTRODUCTION AND METHODS: Hand selection was assessed in preadolescent children (ages 9-11) within a preferential reaching task to delineate the effects of object location, orientation, and task intention on the assessment procedure and compared to data previously acquired from young adults. RESULTS: The observed differences support the notion that children are still in a process of refining their movements in attempt to discern the most efficient and effective patterns of behavior. Notwithstanding differences in performance, similarities between preadolescents and young adults also emerged. Greater right-hand selection in right space and when the handle was oriented to the right indicate that object proximity and orientation influence efficiency and thus constrain hand selection in unimanual object manipulation and role-differentiated bimanual manipulation. CONCLUSIONS: Together, findings add to our understanding of hand preference, unimanual and bimanual object manipulation.

Is Hand Selection Modulated by Cognitive-perceptual Load?

Previous studies proposed that selecting which hand to use for a reaching task appears to be modulated by a factor described as "task difficulty". However, what features of a task might contribute to greater or lesser "difficulty" in the context of hand selection decisions has yet to be determined. There has been evidence that biomechanical and kinematic factors such as movement smoothness and work can predict patterns of selection across the workspace, suggesting a role of predictive cost analysis in hand-selection. We hypothesize that this type of prediction for hand-selection should recruit substantial cognitive resources and thus should be influenced by cognitive-perceptual loading. We test this hypothesis by assessing the role of cognitive-perceptual loading on hand selection decisions, using a visual search task that presents different levels of difficulty (cognitive-perceptual load), as established in previous studies on overall response time and efficiency of visual search. Although the data are necessarily preliminary due to small sample size, our data suggested an influence of cognitive-perceptual load on hand selection, such that the dominant hand was selected more frequently as cognitive load increased. Interestingly, cognitive-perceptual loading also increased cross-midline reaches with both hands. Because crossing midline is more costly in terms of kinematic and kinetic factors, our findings suggest that cognitive processes are normally engaged to avoid costly actions, and that the choice not-to-cross midline requires cognitive resources.

The Effect of Monaural Auditory Stimulus on Hand Selection When Reaching.

This study investigated the effect of monaural auditory stimulus on hand selection when reaching. Healthy right-handed participants were asked to reach to a visual target and were free to use either the right or left hand. A visual target appeared at one of 11 positions in the visual field between -25 and 25 degrees of the horizontal visual angle. An auditory stimulus was given either in the left or right ear 100 ms after the presentation of the visual target, or no auditory stimulus was given. An auditory stimulus in the right ear increased right hand selection, and that in the left ear slightly increased left hand selection when reaching to a target around the midline of the visual field. The horizontal visual angle, where the probabilities of right hand selection and left hand selection were equal when reaching, shifted leftward when an auditory stimulus was given in the right ear, but the angle did not shift in either direction when an auditory stimulus was given in the left ear. The right-ear-dominant auditory stimulus effect on hand selection indicates hemispheric asymmetry of cortical activity for hand selection.

Hand and Grasp Selection in a Preferential Reaching Task: The Effects of Object Location, Orientation, and Task Intention.

As numerous movement options are available in reaching and grasping, of particular interest are what factors influence an individual's choice of action. In the current study a preferential reaching task was used to assess the propensity for right handers to select their preferred hand and grasp a coffee mug by the handle in both independent and joint action object manipulation contexts. Mug location (right-space, midline, and left-space) and handle orientation (toward, away, to left, and to right of the participant) varied in four tasks that differed as a function of intention: (1) pick-up (unimanual, independent); (2) pick-up and pour (bimanual, independent); (3) pick-up and pass (unimanual, joint action); and (4) pick-up, pour and pass (bimanual, joint action). In line with previous reports, a right-hand preference for unimanual tasks was observed. Furthermore, extending existing literature to a preferential reaching task, role differentiation between the hands in bimanual tasks (i.e., preferred hand mobilizing, non-preferred hand stabilizing) was displayed. Finally, right-hand selection was greatest in right space, albeit lower in bimanual tasks compared to what is typically reported in unimanual tasks. Findings are attributed to the desire to maximize biomechanical efficiency in reaching. Grasp postures were also observed to reflect consideration of efficiency. More specifically, within independent object manipulation (pick-up; pick-up and pour) participants only grasped the mug by the handle when it afforded a comfortable posture. Furthermore, in joint action (pick-up and pass; pick-up, pour and pass), the confederate was only offered the handle if the intended action of the confederate was similar or required less effort than that of the participant. Together, findings from the current study add to our knowledge of hand and grasp selection in unimanual and bimanual object manipulation, within the context of both independent and joint action tasks.

Hand preference, performance abilities, and hand selection in children.

It is widely know that the pattern of human handedness is such that approximately 90% of the population is right handed with the remainder being left handed, at least in the adult population. What is less well understood is how handedness develops and at what age adult-like handedness patterns emerge. Quantified in terms of both preference and performance, a plethora of different behavioral assessments are currently in use with both children and adults. Handedness questionnaires are commonly used; however, these possess inherent limitations, considering their subjective nature. Hand performance measures have also been implemented; however, such tasks appear to measure different components of handedness. In addition to these traditional measures, handedness has been successfully assessed through observation of hand selection in reaching, which has proven to be a unique and effective manner in understanding the development of handedness in children. Research over the past several decades has demonstrated that young children display weak, inconsistent hand preference tendencies and are slower with both hands. Performance differences between the hands are larger for young children, and consistency improves with age. However, there remains some controversy surrounding the age at which hand preference and hand performance abilities can be considered fully developed. The following paper will provide a review of the literature pertaining to hand preference, performance abilities and hand selection in children in an attempt to ascertain the age at which adult-like patterns of hand preference and performance emerge.