A synthesis of the characteristics of dance interventions engaging adults with neurodevelopmental disabilities: a scoping review

PURPOSE

Dance can encourage physical activity and promote physical, cognitive, and social development for adults who have neurodevelopmental disabilities (NDD). Dance is defined as a form of expression that may be structured, exploratory, and/or cultural. Current literature supports the benefits of participation in dance for persons with NDD, however less is known about what characteristics support participation in dance.

MATERIALS AND METHODS

A scoping review was conducted to synthesize the characteristics of dance interventions, teaching strategies, and outcome measures used to assess the efficacy of dance interventions. Searches were conducted across six databases and the results were screened according to: i) adults ≥18yrs of age with a diagnosed NDD, and ii) the program incorporated activities that fall within our definition of dance.

RESULTS

A range of dance forms and NDDs were represented across the fourteen studies reviewed. Few provided explicit details of the dance interventions, nor how instruction was adapted. All studies that measured fitness, mobility, balance, posture, and functional activity showed significant improvement. Studies that measured psychosocial and well-being focused on autistic characteristics and showed mixed results.

CONCLUSIONS

Details of interventions, instructions, measures of movement performance, and the relationship between outcomes and the interventions require further development and research.

Immediate effects of myofascial release to the pectoral fascia on posture, range of motion, and muscle excitation: a crossover randomized clinical trial

CONTEXT

Forward shoulder posture (FSP) is a risk factor for shoulder pathology. Manual therapists often use myofascial release (MFR) to elongate restricted pectoral fascia to reduce FSP and improve shoulder function; however, the effects of this treatment approach remain anecdotal.

OBJECTIVE

Determine the acute effects of 4-min of MFR, compared to a soft-touch control (CON), to the pectoral fascia on: 1) FSP, 2) shoulder horizontal abduction ROM (HA-ROM), and 3) muscle excitation of the trapezius (upper, middle, lower [UT, MT, LT]) and pectoralis major (PEC).

METHODS

Fifty-nine right-handed participants (27 ± 9 years, 30 female) with FSP, but otherwise asymptomatic shoulders participated in a randomized crossover clinical trial by attending two experimental sessions: one MFR and one CON treatment, each administered by a Registered Massage Therapist. FSP, HA-ROM, and muscle excitation during a reaching task, were measured before and after each treatment.

RESULTS

There was a significant interaction between treatment and time for FSP (p = .018, ηp = .093) with FSP decreasing from PRE MFR (128 ± 19 mm) to POST MFR (123 ± 19 mm; p < .001, ηp = .420) and PRE CON (126 ± 19 mm) to POST CON (124 ± 18 mm; p < .001, ηp = .191) interventions. There were no significant differences in HA-ROM or muscle excitation.

CONCLUSION

Four minutes of MFR or CON to the pectoral fascia acutely reduces FSP.

Müller-Lyer Illusion susceptibility is conditionally predicted by autistic trait expression

Müller-Lyer (ML) figures bias size estimation consistently, yet different methods can lead to different degrees of illusory bias. Autistic individuals may also be less likely to perceive illusory biases with varying levels of autistic trait expression proposed to modulate reported illusory biases. The Autism-Spectrum Quotient (AQ) and Systemizing Quotient (SQ) are self-report measures that quantify autistic trait expression and systemizing ability in neurotypical individuals. The current study sought to determine if perceptions of illusory size bias negatively correlate with autistic trait expression and the extent to which varying methods of illusion presentation change the magnitude of illusory bias. Thirty neurotypical adults completed both questionnaires as well as four size estimation tasks. Two tasks involved perceptual discrimination of ML figures by concurrent and successive presentation, where participants selected the longer figure by keypress. For Tasks 3 and 4, participants adjusted the size of a non-illusory line (Task 3) or complementary illusory figure (Task 4) to match the perceived length. Overall, task performance was not correlated with autistic trait expression. One exception was a negative correlation with AQ when adjusting a complementary illusory ML figure in Task 4. Illusory biases were also stronger when two illusory figures were presented concurrently. Given these results, illusion susceptibility to the ML is suggested to be reduced with increases in AQ, but only when the method of illusion measurement is adjustment of concurrent illusory figures. Taken together the results provide evidence that traits associated with autism in a neurotypical population may systematically modulate perception.

Dual muscle tendon vibration does not impede performance of a goal-directed aiming task

AIMS

Application of muscle-tendon vibration within the frequency range of 70-120Hz has been studied as a tool to stimulate somatosensory afferents with both the goal of studying human sensorimotor control and of improving post-stroke motor performance. Specific to applications for rehabilitation, current evidence is mixed as to whether dual muscle-tendon vibration is detrimental to the performance of goal-directed upper-limb movements. The current study aimed to determine the effects of muscle-tendon vibration over the wrist flexors and extensors (dual vibration) on performance of a computer goal-directed aiming task.

METHODS

Twenty healthy participants were assigned to the vibration or control group. An aiming task that involved acquiring targets by moving an unseen cursor on a screen was performed. Vision of the cursor and hand were unavailable throughout the four blocks of movement execution. Only the vibration group received dual vibration throughout four blocks. Task performance was assessed using measures of endpoint accuracy and timing. Perceived hand location was assessed using a set of questions and a computerised conscious perception task.

RESULTS

The vibration group had significantly shorter reaction times, without any change in endpoint accuracy, indicating more efficient and effective movement planning. The vibration group did report illusory movement sensation, which was reduced by block 4.

CONCLUSIONS

Dual vibration did not adversely affect aiming accuracy and showed some improvement in reaction time. The present findings support the potential for using dual vibration to stimulate the somatosensory system as participants improved their performance of a novel goal-directed movement. Notably, improvements were maintained when the vibration was removed.

A violation of Fitts' Law occurs when a target range is presented before and during movement

According to Fitts' Law, the time to reach a target (movement time, MT) increases with distance. A violation of Fitts' Law occurs when target positions are outlined before and during movement, as MTs are not different when reaching to the farthest and penultimate targets. One hypothesis posits that performers cognitively process the edges of a target array before the center, allowing for corrective movements to be completed more quickly when moving to edge targets compared to middle targets. The objective of this study was to test this hypothesis by displaying a target range rather than outlines of individual targets in an effort to identify the effects of array edges. Using a touch-screen laptop, participants (N = 24) were asked to reach to one of three targets which would appear within a presented range. Separately, targets were also presented without a range to determine if the display protocol could evoke Fitts' Law. Movements were assessed with the touch screen and optical position measurement. A main effect was found for relative position within a range (touch: F2,44 = 15.4, p < 0.001, η2p = 0.412; position: F2,40 = 15.6, p < 0.001, η2p = 0.439). As hypothesised, MT to the farthest target in a range was not significantly different than MT to the middle target (touch: p = 0.638, position: p = 0.449). No violation was found when a target range was not presented (touch: p = 0.003, position: p = 0.001). Thus, a target range reproduces the Fitts' Law violation previously documented with individually outlined targets, which supports and extends the discussed hypothesis.

Adapting to Altered Sensory Input: Effects of Induced Paresthesia on Goal-Directed Movement Planning and Execution

The current study investigated how temporarily induced paresthesia in the moving limb affects the performance of a goal-directed target aiming task. Three-dimensional displacement data of 14 neurotypical participants were recorded while they pointed to a target on a computer monitor in four conditions: (i) paresthesia-full-vision; (ii) paresthesia-without-target vision; (iii) no-paresthesia-full-vision; (iv) no paresthesia-without-target vision. The four conditions were blocked and counterbalanced such that participants performed the paresthesia and no-paresthesia conditions on two separate days. To assess how aiming performance changed in the presence of paresthesia, we compared early versus late performance (first and last 20% of trials). We found that endpoint accuracy and movement speed were reduced in the presence of paresthesia, but only without target vision. With repetition, participants adjusted their movement performance strategy, such that with induced paresthesia, they used a movement strategy that included more pre-planned movements that depended less on online control.

Optimizing Movement Performance with Altered Sensation: An Examination of Multisensory Inputs

Two experiments were conducted to assess the impact of induced paresthesia on movement parameters of goal-directed aiming movements to determine how visual and auditory feedback may enhance performance when somatosensory feedback is disrupted. In both experiments, neurotypical adults performed the goal-directed aiming task in four conditions: (i) paresthesia-full vision; (ii) paresthesia-no vision; (iii) no paresthesia-full vision; (iv) no paresthesia-no vision. Targets appeared on a computer screen, vision was obscured using visual occlusion spectacles, and paresthesia was induced with a constant current stimulator. The first and last 20% of trials (early and late performance) were compared to assess adaptability to altered somatosensory input. Experiment 2 added an auditory tone that confirmed successful target acquisitions. When compared to early performance in the no-paresthesia and no-vision conditions, induced paresthesia and no vision led to significantly larger endpoint error toward the body midline in both early and late performance. This finding reveals the importance of proprioceptive input for movement accuracy in the absence of visual feedback. The kinematic results indicated that vision could not fully compensate for the disrupted proprioceptive input when participants experienced induced paresthesia. However, when auditory feedback confirmed successful aiming movements in Experiment 2, participants were able to improve their endpoint variability when experiencing induced paresthesia through changes in movement preparation.

A Violation of Fitts' Law is Maintained in Ecologically Valid Settings

A 'violation' of Fitts' Law, or Fitts' Equation, occurs when each potential target location is outlined before and during a reaching movement. Past studies have measured the violation in highly controlled laboratory environments, limiting the generalizability of findings. The purpose of the study was to replicate the violation of Fitts' Equation in the homes of participants using a novel portable apparatus during the COVID-19 pandemic. Movements were measured independently with an accelerometer and touch screen, which allowed for kinematic, temporal, and spatial outcomes to be measured in remote environments. The violation of Fitts' Equation was found with the touch and acceleration measurements and was thus seen in ecologically valid environments. The apparatus used may be used as a model for future field research.

Sensorimotor integration and motor learning during a novel force-matching task in young adults with attention-deficit/hyperactivity disorder

Introduction

Attention-Deficit/Hyperactivity Disorder (ADHD) is a neurodevelopmental disorder that exhibits unique neurological and behavioral characteristics. Those with ADHD often have noted impairments in motor performance and coordination, including during tasks that require force modulation. The present study provides insight into the role of altered neural processing and SMI in response to a motor learning paradigm requiring force modulation and proprioception, that previous literature has suggested to be altered in those with ADHD, which can also inform our understanding of the neurophysiology underlying sensorimotor integration (SMI) in the general population.

Methods

Adults with ADHD (n = 15) and neurotypical controls (n = 15) performed a novel force-matching task, where participants used their right-thumb to match a trace template that varied from 2-12% of their Abductor Pollicis Brevis maximum voluntary contraction. This motor task was completed in pre, acquisition, and post blocks. Participants also completed a retention test 24 h later. Median nerve somatosensory-evoked potentials (SEPs) were collected pre and post motor acquisition. SEPs were stimulated at two frequencies, 2.47 Hz and 4.98 Hz, and 1,000 sweeps were recorded using 64-electrode electroencephalography (EEG) at 2,048 Hz. SEP amplitude changes were normalized to each participant's baseline values for that peak.

Results

Both groups improved at post measures (ADHD: 0.85 ± 0.09; Controls: 0.85 ± 0.10), with improvements maintained at retention (ADHD: 0.82 ± 0.11; Controls: 0.82 ± 0.11). The ADHD group had a decreased N18 post-acquisition (0.87 ± 0.48), while the control N18 increased (1.91 ± 1.43). The N30 increased in both groups, with a small increase in the ADHD group (1.03 ± 0.21) and a more pronounced increase in controls (1.15 ± 0.27).

Discussion

Unique neural differences between groups were found after the acquisition of a novel force-matching motor paradigm, particularly relating to the N18 peak. The N18 differences suggest that those with ADHD have reduced olivary-cerebellar-M1 inhibition when learning a novel motor task dependent on force-modulation, potentially due to difficulties integrating the afferent feedback necessary to perform the task. The results of this work provide evidence that young adults with ADHD have altered proprioceptive processing when learning a novel motor task when compared to neurotypical controls.

Source Localization of Audiovisual Multisensory Neural Generators in Young Adults with Attention-Deficit/Hyperactivity Disorder

Attention-Deficit/Hyperactivity Disorder (ADHD) is a neurodevelopmental disorder that exhibits unique neurological and behavioural characteristics. Our previous work using event-related potentials demonstrated that adults with ADHD process audiovisual multisensory stimuli somewhat differently than neurotypical controls. This study utilised an audiovisual multisensory two-alternative forced-choice discrimination task. Continuous whole-head electroencephalography (EEG) was recorded. Source localization (sLORETA) software was utilised to determine differences in the contribution made by sources of neural generators pertinent to audiovisual multisensory processing in those with ADHD versus neurotypical controls. Source localization techniques elucidated that the controls had greater neural activity 164 ms post-stimulus onset when compared to the ADHD group, but only when responding to audiovisual stimuli. The source of the increased activity was found to be Brodmann Area 2, postcentral gyrus, right-hemispheric parietal lobe referenced to Montreal Neurological Institute (MNI) coordinates of X = 35, Y = −40, and Z = 70 (p < 0.05). No group differences were present during either of the unisensory conditions. Differences in the integration areas, particularly in the right-hemispheric parietal brain regions, were found in those with ADHD. These alterations may correspond to impaired attentional capabilities when presented with multiple simultaneous sensory inputs, as is the case during a multisensory condition.

Rhythmic and non-rhythmic auditory precues: Multiple mechanisms mediating movement performance

Rhythmic auditory stimuli presented before a goal-directed movement have been found to improve temporal and spatial movement outcomes. However, little is known about the mechanisms mediating these benefits. The present experiment used three types of auditory stimuli to probe how improved scaling of movement parameters, temporal preparation and an external focus of attention may contribute to changes in movement performance. Three types of auditory stimuli were presented for 1200 ms before movement initiation; three metronome beats (RAS), a tone that stayed the same (tone-same), a tone that increased in pitch (tone-change) and a no sound control, were presented with and without visual feedback for a total of eight experimental conditions. The sound was presented before a visual go-signal, and participants were instructed to reach quickly and accurately to one of two targets randomly identified in left and right hemispace. Twenty-two young adults completed 24 trials per blocked condition in a counterbalanced order. Movements were captured with an Optotrak 3D Investigator, and a 4(sound) by 2(vision) repeated measures ANOVA was used to analyze dependant variables. All auditory conditions had shorter reaction times than no sound. Tone-same and tone-change conditions had shorter movement times and higher peak velocities, with no change in trajectory variability or endpoint error. Therefore, rhythmic and non-rhythmic auditory stimuli impacted movement performance differently. Based on the pattern of results we propose multiple mechanisms impact movement planning processes when rhythmic auditory stimuli are present.

Temporal features of goal-directed movements change with source, but not frequency, of rhythmic auditory stimuli

Music and metronomes differentially impact movement performance. The current experiment presented metronome and drum beats in simple and complex rhythms before goal-directed reaching movements, while also quantifying enjoyment. Auditory conditions were completed with and without visual feedback and were blocked and counterbalanced. There were no differences between simple and complex rhythms, indicating that rhythmic information alone is sufficient to benefit performance. The drum elicited shorter movement times and higher peak velocities, without an increase in spatial variability. Reaction times were moderately correlated with ratings of enjoyment. These data provide evidence that the source of an auditory stimulus impacts movement performance of a goal-directed reaching task. Results are contextualized within models of goal-directed reaching to elucidate mechanisms contributing to performance improvements.

Audiovisual Multisensory Processing in Young Adults With Attention-Deficit/Hyperactivity Disorder

Multisensory integration is a fundamental form of sensory processing that is involved in many everyday tasks. Those with Attention-Deficit/Hyperactivity Disorder (ADHD) have characteristic alterations to various brain regions that may influence multisensory processing. The overall aim of this work was to assess how adults with ADHD process audiovisual multisensory stimuli during a complex response time task. The paradigm used was a two-alternative forced-choice discrimination task paired with continuous 64-electrode electroencephalography, allowing for the measurement of response time and accuracy to auditory, visual, and audiovisual multisensory conditions. Analysis revealed that those with ADHD ( n = 10) respond faster than neurotypical controls ( n = 12) when presented with auditory, visual, and audiovisual multisensory conditions, while also having race model violation in early response latency quantiles. Adults with ADHD also had more prominent multisensory processing over parietal-occipital brain regions at early post-stimulus latencies, indicating that altered brain structure may have important outcomes for audiovisual multisensory processing. The present study is the first to assess how those with ADHD respond to multisensory conditions during a complex response time task, and demonstrates that adults with ADHD have unique multisensory processing when assessing both behavioral response time measures and neurological measures.

An external focus of attention compared to an internal focus of attention improves anticipatory postural adjustments among people post-stroke

BACKGROUND

People after stroke often have postural impairments that can increase their risk of falling. Anticipatory postural adjustments (APAs) are changes in the activity of postural muscles prior to a voluntary movement in order to maintain vertical equilibrium. Previous research suggests that improving APAs leads to better postural control and reduces the risk of falls. Despite the importance of APAs and their impairment among people post-stroke, studies that aim to investigate methods for improving APAs are limited. Consistent evidence supports that an external focus of attention compared to an internal focus of attention, yields superior performance of motor skills that include postural control.

RESEARCH QUESTION

What are the effects of adopting different foci of attention on measures of APAs and movement parameters when performing a lower extremity Fitts' task among people post-stroke?

METHODS

Twelve individuals post-stroke performed a lower extremity stepping movement (Fitts' task) while adopting an external focus or an internal focus of attention in a within-subject design. A motion capture system was used to record participants' movement data. Custom software derived movement time (MT), peak velocity (PV), time to peak velocity (ttPV) and variability at endpoint (SD_T). Electromyography was used to measure muscle activity and determine APAs onset and magnitude. For all dependent variables separate repeated measures ANOVAs were conducted to compare performance between foci of attention.

RESULTS

The results showed that an external focus of attention yielded significantly better performance on all outcome measures. The improvement in performance was seen in shorter MT, higher PV, shorter ttPV, smaller SD_T, earlier APAs onset and more efficient APAs magnitude.

SIGNIFICANCE

The changes in outcome measures suggest that adopting an external focus of attention during postural tasks could be an effective strategy for improving balance control among people post-stroke.

Rhythmic auditory stimuli heard before and during a reaching movement elicit performance improvements in both temporal and spatial movement parameters

Rhythmic auditory stimuli (RAS) have been proposed to improve motor performance in populations with and without sensorimotor impairments. However, the reasons for the reported benefits are poorly understood. One idea is that RAS may supplement intrinsic feedback when other sensory input is diminished. The current experiment tested this idea by removing vision during a goal-directed reaching task. We hypothesized that any improvements in movement performance due to the RAS would be greater when vision was removed. Twenty-two typically developing adults performed reaching movements to one of two targets with RAS presented before movement initiation, after movement initiation, both before and after movement initiation, and no sound, all with and without vision. Dependent variables were analyzed using a 2 vision by 2 sound-before by 2 sound-during repeated measures ANOVA. Conditions where the metronome was heard before movement initiation yielded shorter and less variable reaction times compared when there was no sound before the movement. The RAS heard before and during the movement independently impacted spatial aspects of the movement. Sound before movement initiation resulted in smaller endpoint error, primarily in the anterior-posterior axis. Sound during the movement resulted in smaller endpoint error, primarily in the mediolateral axis. In no-vision blocks, inclusion of RAS resulted in improved endpoint performance, indicating that RAS supplemented the motor system. The present results strengthen our understanding of sensory integration underlying reaching performance by demonstrating that sound heard before and during a reaching movement can improve motor performance by supplementing the motor system when vision is unavailable.

Both reaching and grasping are impacted by temporarily induced paresthesia

Along with visual feedback, somatosensory feedback provides the nervous system with information regarding movement performance. Somatosensory system damage disrupts the normal feedback process, which can lead to a pins and needles sensation, or paresthaesia, and impaired movement control. The present study assessed the impact of temporarily induced median nerve paresthaesia, in individuals with otherwise intact sensorimotor function, on goal-directed reaching and grasping movements. Healthy, right-handed participants performed reach and grasp movements to five wooden Efron shapes, of which three were selected for analysis. Participants performed the task without online visual feedback and in two somatosensory conditions: 1) normal; and 2) disrupted somatosensory feedback. Disrupted somatosensory feedback was induced temporarily using a Digitimer (DS7AH) constant current stimulator. Participants' movements to shapes 15 or 30 cm to the right of the hand's start position were recorded using a 3 D motion analysis system at 300 Hz (Optotrak 3 D Investigator). Analyses revealed no significant differences for reaction time. Main effects for paresthaesia were observed for temporal and spatial aspects of the both the reach and grasp components of the movements. Although participants scaled their grip aperture to shape size under paresthaesia, the movements were smaller and more variable. Overall participants behaved as though they perceived they were performing larger and faster movements than they actually were. We suggest the presence of temporally induced paresthaesia affected online control by disrupting somatosensory feedback of the reach and grasp movements, ultimately leading to smaller forces and fewer corrective movements.

Self-Compassion and Psycho-Physiological Recovery From Recalled Sport Failure

Failure inherent to high-performance sport can precipitate emotional distress that can impair athletes’ performance and physical and mental health. Identifying factors that allow athletes to manage failure to sustain their health is critical. Self-compassion, treating oneself kindly in response to failure, may help athletes manage failure; it buffers against negative affective psychological responses, yet athletes often fear self-compassion. It is unknown whether the benefits of self-compassion extend to athletes’ physiological responses to failure and whether fear of self-compassion has an influence on psychological and physiological responses to failure, beyond self-compassion. The purpose of this study was to examine the influence of self-compassion on athletes’ psychological and physiological responses when recalling a sport failure and determine if fear of self-compassion exerted unique effects, beyond self-compassion. Participants (n = 91; M age = 21) were university or national-level athletes. In this laboratory-based, observational study, athletes were connected to a multi-modal biofeedback system to measure physiological responding at baseline, during a stress induction (imagining a past performance failure), and during a recovery period. Physiological responding was assessed according to athletes’ high-frequency heart rate variability (HRV), indexing parasympathetic nervous system activity, during the stress induction and recovery phase. Next, to assess psychological reactivity, athletes completed a series of scales (behavioral reactions, thoughts, and emotions). Regression analyses revealed that self-compassion predicted athletes’ HRV reactivity to the stress induction (β = 0.30, p < 0.05). There was no relationship between self-compassion and HRV recovery. Further, self-compassion predicted adaptive behavioral reactions (β = 0.46, p < 0.01), and negatively predicted maladaptive thoughts (β = −0.34, p < 0.01) and negative affect (β = −0.39, p < 0.01). Fear of self-compassion explained additional variance in some maladaptive thoughts and behavioral reactions. Results suggest that self-compassion promotes adaptive physiological and psychological responses in athletes relative to a recalled sport failure and may have implications for performance enhancement, recovery and health outcomes. Further, addressing athletes’ fears of self-compassion may also be important in promoting optimal psychological recovery.

Effects of training with a neuro-mechano stimulator rehabilitation bicycle on functional recovery and paired-reflex depression of the soleus in individuals with incomplete paralysis: a proof-of-principle study

Aim: The present study describes the training effects of a novel motorized bicycle-like device for individuals with incomplete spinal cord injury. Methods: Participants were five individuals with motor incomplete spinal cord injury (56 ± 7 years). Four of five participants received two 30-min sessions of training: one with, and one without, mechanical stimulation on the plantar surface of the foot; soleus paired H-reflex depression was examined before and after each session. Three of five participants received 24 sessions of 30-min of training (long-training). Following the long-training, balance, walking and spasticity improvements were assessed using validated clinical outcome measures, in addition to the H-reflex assessment. Results: One cycling session with mechanical stimulation yielded 14% and 32% more reflex depression in participants with moderate spasticity (n = 2/4). The same trend was not observed in non-spastic participants (n = 2/4). All participants who participated in the long-training had spasticity and showed reduced spasticity, improved walking speed, endurance and balance. Conclusions: Overall, participants with spasticity showed increased soleus H-reflex suppression after one training session with mechanical stimulation and reduced spasticity scores after long training. We interpret this as evidence that the training influenced both presynaptic and postsynaptic inhibitory mechanisms acting on soleus motoneurons. Therefore, this training has the potential to be a non-invasive complementary therapy to reduce spasticity after incomplete spinal cord injury.

Audiovisual Multisensory Integration and Evoked Potentials in Young Adults With and Without Attention-Deficit/Hyperactivity Disorder

The purpose of this study was to assess how young adults with attention-deficit/hyperactivity disorder (ADHD) process audiovisual (AV) multisensory stimuli using behavioral and neurological measures. Adults with a clinical diagnosis of ADHD (n = 10) and neurotypical controls (n = 11) completed a simple response time task, consisting of auditory, visual, and AV multisensory conditions. Continuous 64-electrode electroencephalography (EEG) was collected to assess neurological responses to each condition. The AV multisensory condition resulted in the shortest response times for both populations. Analysis using the race model (Miller, 1982) demonstrated that those with ADHD had violation of the race model earlier in the response, which may be a marker for impulsivity. EEG analysis revealed that both groups had early multisensory integration (MSI) occur following multisensory stimulus onset. There were also significant group differences in event-related potentials (ERPs) in frontal, parietal, and occipital brain regions, which are regions reported to be altered in those with ADHD. This study presents results examining multisensory processing in the population of adults with ADHD, and can be used as a foundation for future ADHD research using developmental research designs as well as the development of novel technological supports.

Ground reaction forces produced by two different hockey skating arm swing techniques

The arm swing in hockey skating can have a positive effect on the forces produced by each skate, and the resulting velocity from each push off. The main purpose of this study was to measure the differences in ground reaction forces (GRFs) produced from an anteroposterior versus a mediolateral style hockey skating arm swing. Twenty-four elite-level female hockey players performed each technique while standing on a ground-mounted force platform, and all trials were filmed using two video cameras. Force data was assessed for peak scaled GRFs in the frontal and sagittal planes, and resultant GRF magnitude and direction. Upper limb kinematics were assessed from the video using Dartfish video analysis software, confirming that the subjects successfully performed two distinct arm swing techniques. The mediolateral arm swing used a mean of 18.38° of glenohumeral flexion/extension and 183.68° of glenohumeral abduction/adduction while the anteroposterior technique used 214.17° and 28.97° respectively. The results of this study confirmed that the mediolateral arm swing produced 37% greater frontal plane and 33% less sagittal plane GRFs than the anteroposterior arm swing. The magnitudes of the resultant GRFs were not significantly different between the two techniques; however, the mediolateral technique produced a resultant GRF with a significantly larger angle from the direction of travel (44.44°) as compared to the anteroposterior technique (31.60°). The results of this study suggest that the direction of GRFs produced by the mediolateral arm swing more closely mimic the direction of lower limb propulsion during the skating stride.

How Working With a Helpful Versus Less Helpful Confederate Influences Joint-Action in a Pegboard Task

Actors change their movement strategies to complement a coactor's movements when performing cooperative tasks. To further investigate this topic, the authors designed a pegboard task whereby a participant-confederate pair worked together to move a peg from one side of the board to the other. The authors examined how the experience of working with a helpful confederate versus less helpful confederate influenced the participant's movement behavior. Results provide evidence that participants change their movement behaviors in response to the actions of the confederate. Here the human capacity to act in such a manner exemplifies an individual's ability to utilize his or her own action system to understand others and interact to complete joint action tasks. Individuals appear to adapt their behavior to their experiences, and thus may be helpful in some contexts and less helpful in others.

The use of action phrases in individuals with Autism Spectrum Disorder

Previous research has shown that individuals with Autism Spectrum Disorder (ASD) may be able to perceive the intentions of another individual through tool use (e.g., Aldridge et al., 2000; Gonzalez et al., 2013). However, it is not well understood how individuals with ASD respond to an indirect connection between an extrapolated action and the required object. To address this question, we employed action phrases that indirectly provided the contextual information about which object to use. Individuals with ASD, and sex and age matched typically developing peers, were asked to pick which object would be needed to complete the task described in a sentence displayed on a computer screen. Although individuals with ASD exhibited slower response times overall, their accuracy scores were comparable to typically developing individuals. The longer response times support the notion that individuals with ASD may have a harder time disengaging their initial perceived use for the object before considering other inherent action possibilities afforded by the object.

The processing of visual and auditory information for reaching movements

Presenting target and non-target information in different modalities influences target localization if the non-target is within the spatiotemporal limits of perceptual integration. When using auditory and visual stimuli, the influence of a visual non-target on auditory target localization is greater than the reverse. It is not known, however, whether or how such perceptual effects extend to goal-directed behaviours. To gain insight into how audio-visual stimuli are integrated for motor tasks, the kinematics of reaching movements towards visual or auditory targets with or without a non-target in the other modality were examined. When present, the simultaneously presented non-target could be spatially coincident, to the left, or to the right of the target. Results revealed that auditory non-targets did not influence reaching trajectories towards a visual target, whereas visual non-targets influenced trajectories towards an auditory target. Interestingly, the biases induced by visual non-targets were present early in the trajectory and persisted until movement end. Subsequent experimentation indicated that the magnitude of the biases was equivalent whether participants performed a perceptual or motor task, whereas variability was greater for the motor versus the perceptual tasks. We propose that visually induced trajectory biases were driven by the perceived mislocation of the auditory target, which in turn affected both the movement plan and subsequent control of the movement. Such findings provide further evidence of the dominant role visual information processing plays in encoding spatial locations as well as planning and executing reaching action, even when reaching towards auditory targets.

How one breaks Fitts's Law and gets away with it: Moving further and faster involves more efficient online control

Adam, Mol, Pratt, and Fischer (2006) reported what they termed "a violation of Fitts's Law" - when participants aimed to targets in an array, movement times (MTs) to the last target location (highest index of difficulty (ID)) were shorter than predicted by Fitts's Law. Based on the results of subsequent studies in which placeholders were present either during planning and/or execution stages of the movements, it was suggested that the violation may emerge because of context-dependent changes in planning processes. The present study examined this planning explanation by conducting detailed kinematic analyses of movements. Participants performed aiming movements to sets of 3 targets in different placeholder arrays with different movement amplitudes. Consistent with previous Fitts's Law violation findings, MTs were not significantly longer for movements to the last versus middle target location. Interestingly, the pattern of peak limb velocities (typically associated with planning processes) did not mirror the changes in MTs. On the other hand, analyses of the effector's spatial variability during the movement suggested greater involvement of online control processes when the target was in the last position. Based on these results, we suggest that the Fitts' Law violation observed here occurred because of more efficient online control processes.

Motor interactions with another person: do individuals with Autism Spectrum Disorder plan ahead?

Interpersonal motor interactions (joint-actions) occur on a daily basis. In joint-action situations, typically developing (TD) individuals consider the end-goal of their partner and adjust their own movements to accommodate the other person. The movement planning processes required for joint-action may, however, be difficult for individuals with an Autism Spectrum Disorder (ASD) given documented difficulties in performance on theory of mind (ToM) and motor tasks. The goal of this experiment was to determine if individuals with ASD exhibit end-state comfort behaviors similar to their TD peers in joint-action situations. Participants were asked to either pass, place, or use three common tools: a wooden toy hammer, a stick, or a calculator. These tools were selected because the degree of affordance they offer (i.e., the physical characteristics they posses to prompt proper use) ranges from direct (hammer) to indirect (calculator). Participants were asked to pass the tool to a confederate who intended to place the tool down, or use the tool. Variables of interest included beginning and end-state grip orientations of the participant and confederate (comfortable or uncomfortable) as a function of task goal, and the side to which the tool was placed or passed. Similar to Gonzalez et al. (2011), some individuals with ASD maximized their partner's beginning-state comfort by adopting personally uncomfortable postures. That said, their performance was more variable than their TD peers who consistently passed tools in a manner that facilitated comfortable use by the confederate. Therefore, the movement planning processes used to prepare to pass a tool are not stereotypical across all individuals with ASD. We propose that the novel joint-action task described herein provides the basis for testing an important link between motor performance and more complex social and communication behaviors.

Assessment of the postural control strategies used to play two Wii Fit™ videogames

The Nintendo Wii Fit™ may provide an affordable alternative to traditional biofeedback or virtual reality systems for retraining or improving motor function in populations with impaired balance. The purpose of this study was to evaluate postural control strategies healthy individuals use to play Wii Fit™ videogames. Sixteen young adults played 10 trials of Ski Slalom and Soccer Heading respectively. Centre of pressure (COP) excursion and three-dimensional movement data were acquired to determine variability in medial-lateral COP sway and shoulder-pelvic movement. While there was no difference in medial-lateral COP variability between games during trial 1, there was a significant difference after 10 trials. COP sway increased (59-75 mm) for Soccer Heading while it decreased (67-33 mm) for Ski Slalom from trial 1 to trial 10. During Ski Slalom participants demonstrated decreased shoulder and pelvic movement combined with increased pelvic-shoulder coupling. Conversely, participants demonstrated greater initial shoulder tilt when playing Soccer Heading, with no reduction in pelvic rotation and tilt. Participants decreased pelvic and trunk movements when skiing, suggesting a greater contribution of lower extremity control while they primarily used a trunk strategy to play Soccer Heading.

Extending end-state comfort effect: do we consider the beginning state comfort of another?

Sharing a drink or passing a tool to another person is frequently done in our daily lives. However, a second thought is rarely given about how the object should be handed; instead we pay attention to other factors (e.g., the company). This interaction (handing a tool to someone) is interesting, since it may give insight to how motor intentions are predicted. Research has demonstrated that individuals exhibit an end-state comfort effect when manipulating objects, and it is of interest to determine how this is applied to a joint-action paradigm. The purpose of this experiment was to determine if participants would anticipate the confederate's postural requirements and pass tools in a manner that allowed the confederate to have beginning state comfort and thus facilitate the motion sequence as a whole. That is, would the participant incur the cost of the movement by adopting an awkward posture to facilitate the use of the tool by the confederate? The results demonstrated that participants allowed the confederate to adopt a comfortable beginning state comfort on 100% of the trials for all the tools. However, the participants did not sacrifice end-state comfort, demonstrating that the participants were able to plan ahead to both maximize their own end-state comfort and the beginning state comfort of the confederate.

Temporal judgments of immediate and delayed consequences of self-initiated movements

This study was designed to examine the impact of a delay between a self-initiated movement and a subsequent auditory event on temporal judgements of movement or sound onset. Participants watched a red dot move in a clockwise direction around a circle displayed on a computer screen and reported when they had pressed the spacebar or heard a tone. In other conditions, the movement and tone both occurred. Specifically, the tone followed the button press either immediately or after delays of 100, 250, or 400 ms. On some trial blocks, participants were asked to judge the time of the button press and on other blocks the time of the tone. When the tone occurred alone, participants' judgements were accurate. When the movement occurred alone participants exhibited an anticipatory bias. Although a delayed tone had a modest impact on judgements movement initiation, button press judgements were anticipatory in all tone delay conditions. Thusly temporal judgements associated with event binding are affected more by voluntary action than the auditory consequences of that action.

Temporal judgements of internal and external events in persons with and without autism

When participants make judgments about the onset of self-initiated movements they typically report the movement occurred earlier than it had [Obhi, S. S., & Haggard, P. (2004). Free will and free won't. American Scientific, 92, 358-365.]. One interpretation is that feed-forward processes lead to awareness of the movement prior to execution. Because individuals with autism experience reduced preparatory activity prior to a voluntary movement, the present study sought to determine whether these anticipatory biases are exhibited by persons with autism. Participants watched a dot move in a circle and pressed the spacebar any time after one revolution. A tone either followed the participants' voluntary movement or was computer generated. Participants in both groups made anticipatory judgements regarding movement initiation ( approximately 100 ms). When the movement and tone occurred together this anticipatory bias was also present, regardless of which event participants focused on. Individuals with autism appear to have access to a similar representation of voluntary movements, however this representation may be more variable.

How do Individuals with Autism Plan Their Movements?

Two experiments investigated how persons with and without autism plan manual aiming movements when advance information is direct and when strategic planning is required. In Experiment 1 advance information about hand, direction, and/or movement amplitude was manipulated. Reaction times suggested both groups adopted a hierarchical pattern of movement planning. In Experiment 2, participants performed aiming movements to one of two targets that were the same or different size. Participants without autism varied the starting location in anticipation of specific target stimuli whereas participants with autism consistently selected the midpoint. Overall, individuals with autism used advance information to plan their movements when this information was direct. However, their performance became stereotyped when strategies were self-generated.

A kinematic analysis of how young adults with and without autism plan and control goal-directed movements

We examined the planning and control of goal-directed aiming movements in young adults with autism. Participants performed rapid manual aiming movements to one of two targets. We manipulated the difficulty of the planning and control process by varying both target size and amplitude of the movements. Consistent with previous research, participants with autism took longer to prepare and execute movements, particularly when the index of difficulty was high. Although there were no group differences for accuracy, participants with autism exhibited more temporal and spatial variability over the initial phase of the movement even though mean peak accelerations and velocities were lower than for control participants. Our results suggest that although persons with autism have difficulty specifying muscular force, they compensate for this initial variability during limb deceleration. Perhaps persons with autism have learned to keep initial impulses low to minimize the spatial variability that needs to be corrected for during the online control phase of the movement.

The effect of response uncertainty on illusory biases of perception and action

When task requirements were known in advance, Glazebrook et al. [C.M. Glazebrook, V.P. Dhillon, K.M. Keetch, J. Lyons, E. Amazeen, D.J. Weeks, D. Elliott, Perception-action and the Müller-Lyer illusion: amplitude or endpoint bias?, Exp. Brain Res. 160 (2005) 71-78.] demonstrated that perceptual biases associated with the Müller-Lyer illusion resulted from a misperception of figure extent, while manual aiming biases resulted from a misperception of vertex position. In this study, we examined the degree to which prior knowledge of task requirements influenced how participants coded visual-spatial information associated with Müller-Lyer configurations. Specifically, we investigated how illusory biases are affected when uncertainty exists as to whether participants will be required to make a perceptual-cognitive decision about the length of a figure or complete a rapid aiming movement to a figure vertex. Although aiming movements were completed in a similar manner regardless of the prior knowledge condition, perceptual biases were associated with a misperception of extent when the task was known and a misperception of both extent and position when the task was unknown. These findings indicate that people are flexible in the manner in which they code visual-spatial information.

Influence of Endogenous and Exogenous Orientations of Attention on Inhibition of Return in a Cross-Modal Target—Target Aiming Task

The authors conducted 2 experiments in which participants (N = 16 in each) executed successive unimanual aiming movements to target locations that were indicated by the onset of either an auditory or a visual stimulus. In Experiment 1 (exogenous orientation), inhibition of return (IOR) effects were observed, with reliable reaction time (RT) costs associated with movements returning to the same target and a trend toward larger IOR effects in left than in right space. There was no influence of stimulus modality on the magnitude of IOR. IOR was also observed in Experiment 2 (endogenous orientation), except the influence of stimulus modality reliably mediated those effect. In that case, IOR was evident only when the previous modality was visual and the current modality was auditory. Together, the results of those 2 experiments suggest that in situations in which 2 paired movements constitute the response criteria, IOR is both supramodal and lateralized to contralateral space.

The influence of advance information about target location and visual feedback on movement planning and execution

This study was designed to determine if movement planning strategies incorporating the use of visual feedback during manual aiming are specific to individual movements. Advance information about target location and visual context was manipulated using precues. Participants exhibited a shorter reaction time and a longer movement time when they were certain of the target location and that vision would be available. The longer movement time was associated with greater time after peak velocity. Under conditions of uncertainty, participants prepared for the worst-case scenario. That is, they spent more time organizing their movements and produced trajectories that would be expected from greater open-loop control. Our results are consistent with hierarchical movement planning in which knowledge of the movement goal is an essential ingredient of visual feedback utilization.

Visual illusions affect both movement planning and on-line control: A multiple cue position on bias and goal-directed action

Over the last decade, there has been an interest in the impact of visual illusions on the control of action. Much of this work has been motivated by Milner and Goodale's two visual system model of visual processing. This model is based on a hypothesized dissociation between cognitive judgments and the visual control of action. It holds that action is immune to the visual context that provides the basis for the illusion-induced bias associated with cognitive judgments. Recently, Glover has challenged this position and has suggested that movement planning, but not movement execution is susceptible to visual illusions. Research from our lab is inconsistent with both models of visual-motor processing. With respect to the planning and control model, kinematic evidence shows that the impact of an illusion on manual aiming increases as the limb approaches the target. For the Ebbinghaus illusion, this involved a decrease in the time after peak velocity to accommodate the 'perceived' size of the target. For the Müller-Lyer illusion, the influence of the figure's tails increased from peak velocity to the end of the movement. Although our findings contradict a strong version of the two visual systems hypothesis, we did find dissociations between perception and action in another experiment. In this Müller-Lyer study, perceptual decisions were influenced by misjudgment of extent, while action was influenced by misjudgment of target position. Overall, our findings are consistent with the idea that it is often necessary to use visual context to make adjustments to ongoing movements.

Perception-action and the M�ller-Lyer illusion: amplitude or endpoint bias?

Over the past decade there has been a great deal of controversy regarding the relative impact of visual illusions on cognitive judgments and the control of goal-directed action. We report the results of two experiments indicating that perceptual biases associated with the Müller-Lyer illusion involve a misjudgment of amplitude/extent while aiming biases involve error in the specification of a movement endpoint. This dissociation of perception and action is consistent with some aspects of Milner and Goodale's two visual system model, but not others.

The Müller-Lyer illusion affects the planning and control of manual aiming movements

Participants made perceptual judgments about the length of, and manual aiming movements to the opposite end of, formerly visible Müller-Lyer stimuli. The Müller-Lyer illusion affected both perceptual judgments and aiming amplitude. Manipulations of stimulus duration (10 ms or 3000 ms) and memory delay length (10 ms or 3000 ms) had no impact on the illusory effect. Aiming movements executed with vision of the hand were less affected by the illusion than movements executed without vision of the hand. The effect of the illusion on aiming amplitude remained the same between peak velocity and the end of the movement even though participants were engaged in on-line control between peak deceleration and the end of the movement. This latter finding was counter to the predictions of a hypothesis (Glover 2002) stating that illusions should only affect the early (planning) stages of movement and not the late (control) stages of movement. We conclude that a single visual representation is used for perception, motor planning, and motor control.