Rapid Aiming Movements Research Articles

Examining the Equivalence Between Imagery and Execution—Does Imagery Comprise the Intended Spatial Trajectory?

The functional equivalence model suggests a common internal representation initiates both imagery and execution. This suggestion is supported by the mental chronometry effect, where there is a positive relation between task difficulty (as defined by the Index of Difficulty; ID) and imagined movement time. The present study extends this logic by examining whether imagery captures the spatial trajectory. Participants were initially tasked with the imagery and execution of a rapid aiming movement under different IDs. These initial attempts were adapted to configure auditory tones at early (25%) and late (75%) intervals for a separate set of imagery trials. If a tone had sounded, participants had to estimate post-trial where their imagined limb would have been located. The findings revealed increases in ID that coincided with increases in imagined and executed movement times. However, participant mean and standard deviation of estimated locations revealed limited differences between the early and late tones. Further inspection revealed some evidence for these estimated locations shifting further along in space following more rapid imagined movements. While equivalence is clearly evident within the temporal domain, there is comparatively little to suggest that this logic extends to the resolution required for simulating the spatial characteristics of movement.

TAT-HUM: Trajectory analysis toolkit for human movements in Python.

Human movement trajectories can reveal useful insights regarding the underlying mechanisms of human behaviors. Extracting information from movement trajectories, however, can be challenging because of their complex and dynamic nature. The current paper presents a Python toolkit developed to help users analyze and extract meaningful information from the trajectories of discrete rapid aiming movements executed by humans. This toolkit uses various open-source Python libraries, such as NumPy and SciPy, and offers a collection of common functionalities to analyze movement trajectory data. To ensure flexibility and ease of use, the toolkit offers two approaches: an automated approach that processes raw data and generates relevant measures automatically, and a manual approach that allows users to selectively use different functions based on their specific needs. A behavioral experiment based on the spatial cueing paradigm was conducted to illustrate how one can use this toolkit in practice. Readers are encouraged to access the publicly available data and relevant analysis scripts as an opportunity to learn about kinematic analysis for human movements.

Movement Kinematics and Interjoint Coordination Are Influenced by Target Location and Arm in 6-Year-Old Children.

Rapid aiming movements are typically used to study upper limb motor control and development. Despite the large corpus of work in this area, few studies have examined kinematic manual asymmetries in children who have just started formal schooling and until now, none have characterized how children coordinate their joints to complete these movements (i.e., interjoint coordination). In the present study, manual asymmetries in kinematics and interjoint coordination in strongly right-handed 6-year-old children were investigated when reaching for ipsilateral and contralateral targets with their dominant right arm and the non-dominant left arm. Overall, manual asymmetries in interjoint coordination are apparent for both 6-year-old children and young adults, although young children completed the task by adopting a different strategy than adults. Also, control strategies employed by 6-year-old children were influenced by both the location of the target as well as the arm used to perform the task. Specifically, compared to all other conditions, children’s trajectories were more curved when performing contralateral movements with the non-dominant left arm, which were driven by smaller shoulder excursions combined with larger elbow excursions for this condition. Based on these results, we argue that the differences in interjoint coordination reflect the stage of development of 6-year-old children, the origin of which derives from maturational (e.g., hand dominance) and environmental factors (e.g., school-based experience).

Energy minimization within target-directed aiming: the mediating influence of the number of movements and target size

In target-directed aiming, performers tend to more greatly undershoot targets when aiming down compared to up because they try to avoid an overshoot error and subsequently minimize the time and energy expenditure that is required to suddenly combat gravitational forces. The present study aims to further examine this principle of time and energy minimization by directly mediating the perceived cost of potential errors as well as the likelihood of their occurrence by manipulating the number of movements and target size, respectively. Participants executed rapid aiming movements in the up/down direction as part of a one-/two-target movement towards a small/large target. Primary movement endpoints showed greater undershooting when aiming in the downward compared to upward direction and small compared to large targets. Meanwhile, the overall movement time showed that slower movements were generated for down compared to up, but only when aiming toward large targets. The failure to mediate the central tendency as a function of the number of movements and target size indicates that the feature of minimization is highly prominent within the performers’ pre-response planning. However, the continued minimization of energy in the presence of large targets may inadvertently cost the movement time.

EP 84. Motor control and learning strategy for efficient neurorehabilitation

Introduction Parkinson’s, stroke, and other neurological diseases may significantly affect the control of voluntary, ballistic-like movements that normally are performed automatically and optimally as regards position accuracy, energy expenditure and movement execution time. The control functions (neural signals to muscles) are to be re-learnt and re-optimised with respect to these performance indices. In our study, a natural approach for efficient motor learning in goal-directed motion tasks, incl. walking is proposed. It is based on novel concepts and underlying principles of neurophysiology, natural dynamics, and biological cybernetics. We believe that such a motor control and learning strategy may be very useful to achieve efficiency in neurorehabilitation. Method Test control functions that could sensibly optimize motor performance have a triphasic (burst-pause-burst) shape. Their parameters are intrinsic ones that human has to (re-) learn in dynamic point-to-point motion tasks, ( Karniel and Inbar, 1997 ). The control learning scheme has the following main steps, ( Kiryazov and Kiriazov, 2010 ): (1) parameterise test control functions; (2) select most appropriate pairs of control parameters and controlled outputs; (3) make corrections in the control parameters until reach the target, applying simple, natural learning algorithm, within a very low number of trials. Results Using realistic mathematical models, our motor learning approach was applied to motion tasks like reaching movements, Fig. 1 , and performing steps. In the latter case, we decomposed the task to perform a step into two point-to-point leg movements, Fig. 2 . In the computer simulations we verified our control concepts and the fact that the learning control process is fast converging. In addition, we did some real (able-bodied) experiments with rapid aiming movements of the arm and they confirm the feasibility and efficacy of the proposed approach. Discussion Based on the conceptual framework above proposed it is possible to design reliable control strategies in neurorehabilitation, ( Despotova and Kiriazov, 2015 ). The neural structures that compute the required control forces are the so-called internal models, and we believe that the proposed approach can be used to rebuild such models (cortical reorganization) by proper training procedures. Recent research has shown that voluntary exercises can increase levels of brain-derived neurotrophic factor and other growth factors, stimulate neurogenesis, and improve brain plasticity and motor learning performance. Conclusion Our approach can also be used for the purposes of neuro-muscular rehabilitation, with assistive robotic devices applied or in functional electrical stimulation. In the latter case, optimising the timing sequence for stimulating muscles may produce smoother and more accurate movements. Another interesting problem is the design of brain-computer interfaces for direct control of human/robot motion and this is a subject of ongoing research.

Altered social attention in anorexia nervosa during real social interaction.

The capacity to devote attentional resources in response to body-related signals provided by others is still largely unexplored in individuals with Anorexia Nervosa (AN). Here, we tested this capacity through a novel paradigm that mimics a social interaction with a real partner. Healthy individuals (Experiment 1) and individuals with AN (Experiment 2) completed a task with another person which consisted in performing, alternatively, rapid aiming movements to lateralised targets. Generally, this task leads to a form of Inhibition of Return (IOR), which consists of longer reaction times when an individual has to respond to a location previously searched by either himself (individual IOR) or by the partner (social IOR) as compared to previously unexplored locations. IOR is considered as an important attentional mechanism that promotes an effective exploration of the environment during social interaction. Here, healthy individuals displayed both individual and social IOR that were both reliable and of the same magnitude. Individuals with AN displayed a non-significant individual IOR but a reliable social IOR that was also significantly stronger than individual IOR. These results suggest the presence of a reduced sensitivity in processing body-related stimuli conveyed by oneself in individuals with AN which is reflected in action-based attentional processes.

Combined visual illusion effects on the perceived index of difficulty and movement outcomes in discrete and continuous fitts' tapping.

The speed-accuracy trade-off is a fundamental movement problem that has been extensively investigated. It has been established that the speed at which one can move to tap targets depends on how large the targets are and how far they are apart. These spatial properties of the targets can be quantified by the index of difficulty (ID). Two visual illusions are known to affect the perception of target size and movement amplitude: the Ebbinghaus illusion and Muller-Lyer illusion. We created visual images that combined these two visual illusions to manipulate the perceived ID, and then examined people's visual perception of the targets in illusory context as well as their performance in tapping those targets in both discrete and continuous manners. The findings revealed that the combined visual illusions affected the perceived ID similarly in both discrete and continuous judgment conditions. However, the movement outcomes were affected by the combined visual illusions according to the tapping mode. In discrete tapping, the combined visual illusions affected both movement accuracy and movement amplitude such that the effective ID resembled the perceived ID. In continuous tapping, none of the movement outcomes were affected by the combined visual illusions. Participants tapped the targets with higher speed and accuracy in all visual conditions. Based on these findings, we concluded that distinct visual-motor control mechanisms were responsible for execution of discrete and continuous Fitts' tapping. Although discrete tapping relies on allocentric information (object-centered) to plan for action, continuous tapping relies on egocentric information (self-centered) to control for action. The planning-control model for rapid aiming movements is supported.

The Gambler's Fallacy: A Basic Inhibitory Process?

Two studies were conducted to examine the relation between the gambler’s fallacy (GF) and attentional processes associated with inhibition of return (IOR). In Study 1, participants completed rapid aiming movements to equally probable targets presented to the left and right. They also completed a gambling protocol in which they bet on the illumination of either target. Consistent with the IOR phenomenon, participants were slower to initiate their movements on trial N + 1 when the target was the same as trial N. Participants with more pronounced IOR were more likely to switch betting behavior after a win than participants with a smaller index. This betting behavior was also related to a GF index measured by a questionnaire. In Study 2, participants performed both the aiming task and the betting task with a partner. Each participant performed two trials before ceding to the partner. Thus we were able to examine IOR and betting behavior as a function of the participant’s own previous trial and their partner’s previous trial. The IOR effect was robust both within and between-participants. Participants were more likely to maintain their bet following an unsuccessful outcome regardless of whether it was their own outcome or their partner’s outcome. This type of betting behavior is consistent with the GF. Individual IOR scores were a reliable predictor of betting behavior and the questionnaire was also successful in predicting behavior. In addition, the within-person IOR indices covaried with the GF index derived from the questionnaire. In summary, there appears to be a relation between IOR and the GF. We suggest that early humans developed specialized attentional systems to deal with non-random environmental contingencies, and that the automatic processes associated with these systems are sometimes maladaptive in artificial environments in which the same contingencies do not hold.

An investigation of upper limb motor function in high functioning autism and Asperger's disorder using a repetitive Fitts’ aiming task

There is now a growing body of research examining movement difficulties in children diagnosed with high functioning autism (HFA) and Asperger's disorder (AD). Despite this, few studies have investigated the kinematic components of movement that may be disrupted in children diagnosed with these disorders. The current study investigated rapid aiming movements in 19 individuals diagnosed with HFA, 20 individuals diagnosed with AD and 18 typically developing (TD) controls. A novel touchscreen version of a Fitts’ aiming task was administered that required participants to make 10 reciprocal aiming movements between targets. Task difficulty was manipulated by varying the size and distance between targets. Movement time in the HFA and AD groups was comparable to TD controls. Children with HFA displayed more constant and variable error across repeated aiming attempts compared to the TD group that may be attributed to deficits in feedforward online refinement of movement. These findings are in accordance with previous gait, ocular motor, upper limb and neuroimaging studies that suggest that the cerebellum may underlie movement disturbance in individuals diagnosed with HFA. Additionally, differences in the nature of upper limb motor disturbance in HFA may serve as a useful future adjunct to clinical measures.

Detecting and Correcting Errors in Rapid Aiming Movements

According to closed-loop accounts of motor control, movement errors are detected by comparing sensory feedback to an acquired reference state. Differences between the reference state and the movement-produced feedback results in an error signal that serves as a basis for a correction. The main question addressed in the current study was how distance, movement time, and velocity influence both spatial or temporal error detection. Forty college-aged participants (30 women and 10 men) performed rapid aiming movements over 30° or 50° in either 210 ms or 350 ms without vision. The participants verbally estimated the distance moved and the movement time during acquisition before knowledge of results was given and during an immediate retention test without knowledge of results. Spatial and temporal objective-subjective correlations were greater in the 210-ms condition compared to the 350-ms condition, but were not related to movement velocity.

Detecting and Correcting Errors in Rapid Aiming Movements: Effects of Movement Time, Distance, and Velocity

Detecting and Correcting Errors in Rapid Aiming Movements: Effects of Movement Time, Distance, and Velocity

Concurrent Visual Feedback, Practice Organization, and Spatial Aiming Accuracy in Rapid Movement Sequences

While the availability of visual feedback is a well-known factor influencing the accuracy of rapid aiming movements, little is known about how vision might interact with a contextual variable like practice organization. In the current study, the interaction of concurrent visual feedback (CVF) and practice organization on aiming movement accuracy was investigated in the dominant limb of 40 college-aged participants. Participants performed “triplets” of rapid aiming movements with a lightweight lever in the sagittal plane involving short (20°), medium (40°), long (60°) distances and were randomly assigned to one of four groups (n=10) in a 2 (Group: Blocked Practice, Random Practice) x 2 (Vision: CVF, no CVF) factorial design. Participants performed 24 triplets in acquisition and 10 triplets of a novel pattern (15°- 45°-15°) on transfer. Movement time was controlled by a metronome set at 1.43 cycles per second resulting in a cycle time of approximately 700 ms per movement. The constant error and overall error in distance were calculated for each distance and analyzed with separate 2 (Group) x 2 (Vision) x 3 (Movement) ANOVAs with repeated measures on the last factor. When CVF was available, contextual interference effects were shown by better accuracy for the blocked practice groups during acquisition compared to the random practice group. Without CVF, participants tended to overshoot the targets and contextual interference effects were minimized during acquisition and on the first transfer trial. Random practice resulted in better transfer performance compared to blocked practice for both vision conditions when all transfer trials were included in the analysis. The findings contributed to the current literature by demonstrating the importance of practice context and visual feedback to aiming accuracy.

Planning of rapid aiming movements and the contingent negative variation: Are movement duration and extent specified independently?

In the present study we investigated motor programming constraints implied by the Generalized Motor Program (GMP) view. A response precuing task was used in which participants performed aiming movements of either short or long duration to either a near or a far target position. Precues provided either no advance information or partial information about extent or duration or fully specified the aiming movement. Reaction time (RT) decreased and late Contingent Negative Variation (CNV) amplitude increased with the amount of advance information. In contrast to predictions of the GMP view, the extent precue led to faster responses and larger CNV amplitude than the duration precue. We conclude that late CNV amplitude reflects independent parameter specification processes at an abstract level at which GMP's motor programming constraints do not apply.

Optimising speed and energy expenditure in accurate visually directed upper limb movements

Traditional models of speed–accuracy relations and limb control are steady-state models that fail to consider the learning history and strategic approach of the performer. Work from this laboratory indicates that a performer adjusts his/her behaviour from trial-to-trial to optimise not only the speed and accuracy of performance, but also energy expenditure. Because some errors have greater temporal and energy costs than others, most performers execute movements that are prepared such that potential errors are of minimal expense. The trajectories and subsequent endpoint distributions of rapid aiming movements depend on advance knowledge about the availability of afferent information for online control, as well as the costs associated with undershooting or overshooting the target position with the initial impulse. With practice, a performer is able to reduce the trial-to-trial variability associated with goal-directed movement through more consistent movement planning processes and more rapid online control. Part of the optimisation process is related to the development of an internal model of performance against which early afferent feedback can be evaluated. This framework for examining speed, accuracy and energy expenditure in goal-directed reaching can be used to help understand the breakdown of efficient limb control due to fatigue, ageing and pathology.

Spatial Error Detection in Rapid Unimanual and Bimanual Aiming Movements

According to closed-loop accounts of motor control, movement errors are detected by comparing sensory feedback to an acquired reference state. Differences between the reference state and the movement-produced feedback results in an error signal which serves as a basis for a correction. The current study assessed whether error detection is less accurate when feedback from both hands must be analyzed compared to one hand and if error detection is more accurate in longer movements compared to shorter movements. 36 college-age participants (26 women and 10 men) performed a rapid aiming movement of varying distances with one hand or both hands simultaneously. Participants verbally estimated the distance moved on all trials before knowledge of results was given. Error detection was measured by the correlation and the mean absolute difference between the actual and estimated distance. Error detection was not more accurate for the longer movements, and participants underestimated errors in all conditions. Strong positive correlations were shown for both unimanual and bimanual aiming tasks, suggesting that two streams of sensory information can be processed concurrently.

Poster 72: Rapid Aiming Movements by Senior Adults: Implications for Environmental Design and Intervention Strategies

Objective: To investigate how task complexity and vision (functions critical for engaging in everyday tasks) influenced a rapid aiming task performed by a group of healthy senior adults. Design: A 1-group, experimental, repeated-measures design manipulating task complexity and visual information conditions across and within subjects. Setting: A research lab within an academic medical center. Participants: 18 healthy senior adults between the ages of 60 and 80. Interventions: Each participant was asked to move a stylus as quickly and as accurately as possible across different task demands and with vision available and not available.

Electromyographic Control of Movement Time in a Rapid Aiming Movement

One of the major issues to emerge from research on human-limb movement is the manner in which the central nervous system regulates electromyographic (EMG) activity to produce movements that differ in duration and distance. Different models of control predict different relations between EMG characteristics and movement kinematics, particularly with regard to the role of EMG burst duration and movement time. However, models have been evaluated with means averaged over individuals and across large numbers of practice trials. The goal of this study was to assess how well individual subjects' data conform to the predictions of the control models. Participants (n = 4) performed an elbow flexion and extension task over 45 degrees in movement times between 90 and 260 msec. EMG amplitude and EMG burst duration from the right elbow flexors were correlated with movement time for each individual. As expected, movement time was positively correlated with EMG burst duration and negatively correlated with EMG amplitude, with wider ranges in the EMG burst duration-movement time correlations across participants. Data from all participants supported predictions of the impulse-timing control model, but the slopes of the studied relations varied across participants.

The effect of continuous, nonlinearly transformed visual feedback on rapid aiming movements

We investigated the ability to adjust to nonlinear transformations that allow people to control external systems like machines and tools. Earlier research (Verwey and Heuer 2007) showed that in the presence of just terminal feedback participants develop an internal model of such transformations that operates at a relatively early processing level (before or at amplitude specification). In this study, we investigated the level of operation of the internal model after practicing with continuous visual feedback. Participants executed rapid aiming movements, for which a nonlinear relationship existed between the target amplitude seen on the computer screen and the required movement amplitude of the hand on a digitizing tablet. Participants adjusted to the external transformation by developing an internal model. Despite continuous feedback, explicit awareness of the transformation did not develop and the internal model still operated at the same early processing level as with terminal feedback. Thus with rapid aiming movements, the type of feedback may not matter for the locus of operation of the internal model.

Rapid Aiming Movements by Senior Adults

With the increasing aging population and technology advances, occupational therapists and other healthcare professionals are uniquely positioned to examine how changes associated with aging and environmental factors support or constrain the functioning of senior adults. This study investigated how task complexity and vision (functions critical for engaging in everyday tasks) influenced a rapid aiming task performed by a group of healthy senior adults (N = 18) between the ages of 60 and 80. Manipulating task complexity and visual information conditions provided insights into response preparation/reaction time, movement time, total time, and arm velocity profiles. Separate within-subjects design analysis of variance indicated that, with increasing task complexity and a restricted visual environment, senior adults performed more slowly as compared with their performance in a visually enhanced and less complex environment. Consistent with Fitts' law, senior adults' movement time significantly increased as task complexity increased. Moreover, movement time was longer for the no-vision conditions whereas conversely reaction time was shorter in the no-vision conditions. Velocity profiles were similar to those described in the literature on senior adults with flattened peaks and online adjustments evident in the vision conditions, whereas in the no-vision conditions velocity profiles were more symmetric and preplanned. Given that senior adults' aiming performance is affected by age-related changes and environmental complexity, this study provides insights to optimizing their performance in adapting and enhancing simple everyday tasks involving pointing and aiming. Implications include redesign of keyboards or use of accessibility devices to offset their age-related response slowness. Thus, this study provides empirical support to designers for implementing visibility features and varying target sizes to enhance seniors' participation in everyday environments.

The Response Activation Model and Cross-Modal Facilitation and Inhibition of Return: A Trajectory Analysis

Non-informative spatial cues presented prior to a goal-directed movement influence not only movement initiation time but also the spatial characteristics of the movement trajectories. These trajectory effects are thought to stem from an integration of competing motor responses. In the present experiments, trajectories of rapid aiming movements were examined under the constraints of a cue-target inhibition of return (IOR) paradigm. Aiming movements were made to targets that were preceded by a cue stimulus in the same or different location. Four experiments were conducted in which the modality of the cue and target stimulus was manipulated across vision and audition. Although facilitation effects were present under the cross modality protocols, IOR effects were observed only for same cue-target pairings. At short stimulus onset asynchronies, limb trajectories deviated toward the target that had just been cued, particularly when the cue occurred in left space. These trajectory effects are consistent with response activation models of selective attention and movement preparation.