Impaired visuomotor adaptation in adults with ADHD

Visuomotor tracking strategies in children: associations with neurodevelopmental symptoms

Children with neurodevelopmental disorders (NDDs) often display motor problems that may impact their daily lives. Studying specific motor characteristics related to spatiotemporal control may inform us about the mechanisms underlying their challenges. Fifty-eight children with varying neurodevelopmental symptoms load (median age: 5.6 years, range: 2.7-12.5 years) performed an interactive tablet-based tracking task. By investigating digit touch errors relative to the target's movement direction, we found that a load of neurodevelopmental symptoms was associated with reduced performance in the tracking of abrupt alternating directions (zigzag) and overshooting the target. In contrast, reduced performance in children without neurodevelopmental symptoms was associated with lagging behind the target. Neurodevelopmental symptom load was also associated with reduced flexibility in correcting for lateral deviations in smooth tracking (spiral). Our findings suggest that neurodevelopmental symptoms are associated with difficulties in motor regulation related to inhibitory control and reduced flexibility, impacting motor control in NDDs.

A Serious Game for the Assessment of Visuomotor Adaptation Capabilities during Locomotion Tasks Employing an Embodied Avatar in Virtual Reality

The study of visuomotor adaptation (VMA) capabilities has been encompassed in various experimental protocols aimed at investigating human motor control strategies and/or cognitive functions. VMA-oriented frameworks can have clinical applications, primarily in the investigation and assessment of neuromotor impairments caused by conditions such as Parkinson's disease or post-stroke, which affect the lives of tens of thousands of people worldwide. Therefore, they can enhance the understanding of the specific mechanisms of such neuromotor disorders, thus being a potential biomarker for recovery, with the aim of being integrated with conventional rehabilitative programs. Virtual Reality (VR) can be entailed in a framework targeting VMA since it allows the development of visual perturbations in a more customizable and realistic way. Moreover, as has been demonstrated in previous works, a serious game (SG) can further increase engagement thanks to the use of full-body embodied avatars. Most studies implementing VMA frameworks have focused on upper limb tasks and have utilized a cursor as visual feedback for the user. Hence, there is a paucity in the literature about VMA-oriented frameworks targeting locomotion tasks. In this article, the authors present the design, development, and testing of an SG-based framework that addresses VMA in a locomotion activity by controlling a full-body moving avatar in a custom VR environment. This workflow includes a set of metrics to quantitatively assess the participants' performance. Thirteen healthy children were recruited to evaluate the framework. Several quantitative comparisons and analyses were run to validate the different types of introduced visuomotor perturbations and to evaluate the ability of the proposed metrics to describe the difficulty caused by such perturbations. During the experimental sessions, it emerged that the system is safe, easy to use, and practical in a clinical setting. Despite the limited sample size, which represents the main limitation of the study and can be compensated for with future recruitment, the authors claim the potential of this framework as a useful instrument for quantitatively assessing either motor or cognitive impairments. The proposed feature-based approach gives several objective parameters as additional biomarkers that can integrate the conventional clinical scores. Future studies might investigate the relation between the proposed biomarkers and the clinical scores for specific disorders such as Parkinson's disease and cerebral palsy.

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

Attention-deficit/hyperactivity disorder (ADHD) is a neurodevelopmental disorder that has noted alterations to motor performance and coordination, potentially affecting learning processes and the acquisition of motor skills. This work will provide insight into the role of altered neural processing and sensorimotor integration (SMI) while learning a novel visuomotor task in young adults with ADHD. This work compared adults with ADHD (n = 12) to neurotypical controls (n = 16), using a novel visuomotor tracing task, where participants used their right-thumb to trace a sinusoidal waveform that varied in both frequency and amplitude. This learning paradigm was completed in pre, acquisition, and post blocks, where participants additionally returned and completed a retention and transfer test 24 h later. Right median nerve short latency somatosensory-evoked potentials (SEPs) were collected pre and post motor acquisition. Performance accuracy and variability improved at post and retention measures for both groups for both normalized (P < 0.001) and absolute (P < 0.001) performance scores. N18 SEP: increased in the ADHD group post motor learning and decreased in controls (P < 0.05). N20 SEP: increased in both groups post motor learning (P < 0.01). P25: increased in both groups post motor learning (P < 0.001). N24: increased for both groups at post measures (P < 0.05). N30: decreased in the ADHD group and increased in controls (P < 0.05). These findings suggest that there may be differences in cortico-cerebellar and prefrontal processing in response to novel visuomotor tasks in those with ADHD.NEW & NOTEWORTHY Alterations to somatosensory-evoked potentials (SEPs) were present in young adults with attention-deficit/hyperactivity disorder (ADHD), when compared with neurotypical controls. The N18 and N30 SEP peak had differential changes between groups, suggesting alterations to olivary-cerebellar-M1 processing and SMI in those with ADHD when acquiring a novel visuomotor tracing task. This suggests that short-latency SEPs may be a useful biomarker in the assessment of differential responses to motor acquisition in those with ADHD.

How are you getting by? Coping in developmental coordination disorder versus attention-deficit/hyperactivity disorder

Objective

Developmental Coordination Disorder (DCD) and Attention-Deficit/Hyperactivity Disorder (ADHD) persist into adulthood; however, little research exists to describe how adults with DCD and/or ADHD cope with their symptoms. Therefore, the purpose of this study was to investigate coping mechanisms reported by adults with DCD, ADHD, or both conditions. We expected there would be strategies specific to each condition and a broader scope of mechanisms reported by those with co-occurring DCD+ADHD.

Method

N = 161 participants completed the online survey, including n = 31 with DCD only, n = 116 with ADHD only, and n = 14 with DCD+ADHD.

Results

Most participants reported adaptive strategies. Of these, behavioral adaptations were most relevant to ADHD, while environmental modifications were common in DCD. Cognitive reframing and social support were similarly relevant to those with DCD and DCD+ADHD. Coping strategy categories were most uniform for the DCD+ADHD group.

Conclusions

Coping profiles highlight several noteworthy differences between DCD and ADHD which may be relevant for treatment.

Manual dexterity and strength and in young adults with and without Attention-Deficit/Hyperactivity Disorder (ADHD)

Manual motor deficits are common in children with attention deficit/hyperactivity disorder (ADHD); however, it is unclear whether these impairments persist into adulthood. The aim of this study was to examine manual dexterity and strength in young adults with ADHD aged 18-25 years. Sixty-one individuals with confirmed ADHD and 56 adults without ADHD completed Purdue Pegboard tasks for manual dexterity and maximal hand- and pinch-grip tests for strength. In the Purdue Pegboard task, participants placed pins using the right, left, and both-hands, respectively. In addition, participants built assemblies using pins, washers, and collars with alternating hand movements. The results demonstrated that women without ADHD out-performed the other three groups in the right-hand, bimanual, and assembly PPB tasks. Both maximal hand strength tests demonstrated that men were stronger than women, but no differences were observed between adults with and without ADHD. The current findings suggest that adults with ADHD may have deficits in manual dexterity and tasks requiring bimanual coordination.

Aging Effect on Visuomotor Adaptation: Mediated by Cognitive Decline

The question of whether and how aging affects humans’ visuomotor adaptation remains controversial. This study investigates how the effect of aging on visuomotor adaptation is related to age-related cognitive declines. We compared the performance of 100 older people (age: 55–82 years) and 20 young adults (age: 18–27 years) on a visuomotor adaptation task and three cognition tasks. A decline in visuomotor adaptation of older people was well observed. However, this decline was not strongly correlated with chronological age increase but was associated to the age-related declines of cognitive functions and speed of motor planning. We then constructed a structural mediation model in which the declined cognitive resources mediated the effect of age increase on the decline in visuomotor adaptation. The data from the present study was well-explained by the mediation model. These findings indicate that the aging effect on visuomotor adaptation mainly reflects the age-related decline of cognitive functions, which results in insufficient explicit processing on visual perturbation during visuomotor control.

Evoked Potentials Differentiate Developmental Coordination Disorder From Attention-Deficit/Hyperactivity Disorder in a Stop-Signal Task: A Pilot Study

Developmental Coordination Disorder and Attention-Deficit/Hyperactivity Disorder are unique neurodevelopmental disorders with overlaps in executive functions and motor control. The conditions co-occur in up to 50% of cases, raising questions of the pathological mechanisms of DCD versus ADHD. Few studies have examined these overlaps in adults with DCD and/or ADHD. Therefore, to provide insights about executive functions and motor control between adults with DCD, ADHD, both conditions (DCD + ADHD), or typically developed controls, this study used a stop-signal task and parallel EEG measurement. We assessed executive performance via go accuracy and go reaction time, as well as motor response inhibition via stop-signal reaction time. This was complemented with analysis of event-related potentials (ERPs). Based on existing investigations of adults with DCD or ADHD, we expected (1) groups would not differ in behavioral performance on stop and go trials, but (2) differences in ERPs, particularly in components N200 (index of cognitive control) and P300 (index of attention and inhibition) would be evident. The sample included N = 50 adults with DCD (n = 12), ADHD (n = 9), DCD + ADHD (n = 7), and control participants (n = 22). We replicated that there were no between-group differences for behavioral-level executive performance and motor response inhibition. However, on a physiological level, ERP components N200 and P300 differed between groups, particularly during successful response inhibition. These ERPs reflect potential endophenotypic differences not evident in overt behavior of participants with ADHD and/or DCD. This suggests a disorder specific employment of inhibition or general executive functions in groups of adults with DCD, DCD + ADHD, ADHD, or control participants.

Procedural Sequence Learning in Attention Deficit Hyperactivity Disorder: A Meta-Analysis

Previous literature proposes that the motor deficits in Attention Deficit Hyperactivity Disorder (ADHD) may be attributed to impairments of the procedural memory network, a long-term memory system involved in sensorimotor and cognitive skill development. A handful of studies have explored procedural sequence learning in ADHD, but findings have been inconsistent. A meta-analysis was conducted to begin to establish whether procedural sequence learning deficits exist in ADHD. The results of seven studies comprising 213 participants with ADHD and 257 participants with typical development (TD) generated an average standardized mean difference of 0.02 (CI95 -0.35, 0.39) that was not significant. Heterogeneity was significant across studies and could be partially attributed to the age of participants. We argue that procedural sequence learning appears to be preserved in ADHD and discuss potential explanations for and against this finding.

Gut microbiota from persons with attention-deficit/hyperactivity disorder affects the brain in mice

BACKGROUND

The impact of the gut microbiota on host physiology and behavior has been relatively well established. Whether changes in microbial composition affect brain structure and function is largely elusive, however. This is important as altered brain structure and function have been implicated in various neurodevelopmental disorders, like attention-deficit/hyperactivity disorder (ADHD). We hypothesized that gut microbiota of persons with and without ADHD, when transplanted into mice, would differentially modify brain function and/or structure. We investigated this by colonizing young, male, germ-free C57BL/6JOlaHsd mice with microbiota from individuals with and without ADHD. We generated and analyzed microbiome data, assessed brain structure and function by magnetic resonance imaging (MRI), and studied mouse behavior in a behavioral test battery.

RESULTS

Principal coordinate analysis showed a clear separation of fecal microbiota of mice colonized with ADHD and control microbiota. With diffusion tensor imaging, we observed a decreased structural integrity of both white and gray matter regions (i.e., internal capsule, hippocampus) in mice that were colonized with ADHD microbiota. We also found significant correlations between white matter integrity and the differentially expressed microbiota. Mice colonized with ADHD microbiota additionally showed decreased resting-state functional MRI-based connectivity between right motor and right visual cortices. These regions, as well as the hippocampus and internal capsule, have previously been reported to be altered in several neurodevelopmental disorders. Furthermore, we also show that mice colonized with ADHD microbiota were more anxious in the open-field test.

CONCLUSIONS

Taken together, we demonstrate that altered microbial composition could be a driver of altered brain structure and function and concomitant changes in the animals' behavior. These findings may help to understand the mechanisms through which the gut microbiota contributes to the pathobiology of neurodevelopmental disorders. Video abstract.

Finger tapping and pre-attentive sensorimotor timing in adults with ADHD

Sensorimotor timing deficits are considered central to attention-deficit/hyperactivity disorder (ADHD). However, the tasks establishing timing impairments often involve interconnected processes, including low-level sensorimotor timing and higher level executive processes such as attention. Thus, the source of timing deficits in ADHD remains unclear. Low-level sensorimotor timing can be isolated from higher level processes in a finger-tapping task that examines the motor response to unexpected shifts of metronome onsets. In this study, adults with ADHD and ADHD-like symptoms (n = 25) and controls (n = 26) performed two finger-tapping tasks. The first assessed tapping variability in a standard tapping task (metronome-paced and unpaced). In the other task, participants tapped along with a metronome that contained unexpected shifts (±15, 50 ms); the timing adjustment on the tap following the shift captures pre-attentive sensorimotor timing (i.e., phase correction) and thus should be free of potential higher order confounds (e.g., attention). In the standard tapping task, as expected, the ADHD group had higher timing variability in both paced and unpaced tappings. However, in the pre-attentive task, performance did not differ between the ADHD and control groups. Together, results suggest that low-level sensorimotor timing and phase correction are largely preserved in ADHD and that some timing impairments observed in ADHD may stem from higher level factors (such as sustained attention).

Deficits in inhibitory force control in young adults with ADHD

Poor inhibitory control is a well-established cognitive correlate of adults with ADHD. However, the simple reaction time (RT) task used in a majority of studies records performance errors only via the presence or absence of a single key press. This all-or-nothing response makes it impossible to capture subtle differences in underlying processes that shape performance. Subsequently, all-or-nothing tasks may underestimate the prevalence of executive function deficits in ADHD. The current study measured inhibitory control using a standard Go/No-Go RT task and a more sensitive continuous grip force task among adults with (N=51, 22 female) and without (N=51, 29 female) ADHD. Compared to adults without ADHD, adults with ADHD made more failed inhibits in the classic Go/No-Go paradigm and produced greater and more variable force during motor inhibition. The amount of force produced on failed inhibits was a stronger predictor of ADHD-related symptoms than the number of commissions in the standard RT task. Adults with ADHD did not differ from those without ADHD on the mean force and variability of force produced in Go trials. These findings suggest that the use of a precise and continuous motor task, such as the force task used here, provides additional information about the nature of inhibitory motor control in adults with ADHD.

Memory-guided force output is associated with self-reported ADHD symptoms in young adults

Attention-deficit/hyperactivity disorder (ADHD) is the most commonly diagnosed mental health disorder in childhood and persists into adulthood in up to 65 % of cases. ADHD is associated with adverse outcomes such as the ability to gain and maintain employment and is associated with an increased risk for substance abuse obesity workplace injuries and traffic accidents A majority of diagnosed children have motor deficits; however, few studies have examined motor deficits in young adults. This study provides a novel examination of visuomotor control of grip force in young adults with and without ADHD. Participants were instructed to maintain force production over a 20-second trial with and without real-time visual feedback about their performance. The results demonstrated that when visual feedback was available, adults with ADHD produced slightly higher grip force than controls. However, when visual feedback was removed, adults with ADHD had a faster rate of decay of force, which was associated with ADHD symptom severity and trait impulsivity. These findings suggest that there may be important differences in the way that adults with ADHD integrate visual feedback during continuous motor tasks. These may account for some of the motor impairments reported in children with ADHD. These deficits could result from (1) dysfunctional sensory motor integration and/or (2) deficits in short-term visuomotor memory.