Saccade adaptation in young people diagnosed with Attention Deficit Hyperactivity Disorder Combined Type

The ability to maintain rhythm is predictive of ADHD diagnosis and profile

Attention deficit hyperactivity disorder (ADHD) is the most prevalent neuropsychiatric disorder in the world. Currently, the diagnosis is based mainly on interviews, resulting in uncertainties in the clinical assessment. While some neuropsychological tests are used, their specificity and selectivity are low, and more reliable biomarkers are desirable. Previous research indicates that ADHD is associated with morphological changes in the cerebellum, which is essential for motor ability and timing. Here, we compared 29 children diagnosed with ADHD to 96 age-matched controls on prism adaptation, eyeblink conditioning, and timed motor performance in a finger tapping task. Prism adaptation and timing precision in the finger tapping task, but not performance on eyeblink conditioning, differed between the ADHD and control groups, as well as between children with and without Deficits in Attention, Motor control, and Perception (DAMP) - a more severe form of ADHD. The results suggest finger tapping can be used as a cheap, objective, and unbiased biomarker to complement current diagnostic procedures.

The Eyes Have It: A Meta-analysis of Oculomotor Inhibition in Attention-Deficit/Hyperactivity Disorder

BACKGROUND

Diminished inhibitory control is one of the main characteristics of attention-deficit/hyperactivity disorder (ADHD), and impairments in oculomotor inhibition have been proposed as a potential biomarker of the disorder. The present meta-analysis summarizes the effects reported in studies comparing oculomotor inhibition in ADHD patients and healthy control subjects.

METHODS

Inhibitory outcomes were derived from oculomotor experimental paradigms including the antisaccade (AS), memory-guided saccade, and prolonged fixation tasks. Temporal and spatial measures were also extracted from these tasks and from visually guided saccade tasks as secondary outcomes. Data were available from k = 31 studies (N = 1567 participants). Summary effect sizes were computed using random-effects models and a restricted maximum-likelihood estimator.

RESULTS

Among inhibitory outcomes, direction errors in AS, after correcting for publication bias, showed a moderate effect and large between-study heterogeneity (k = 18, n = 739, g = 0.57, 95% confidence interval [CI] [0.27, 0.88], I²= 74%); anticipatory saccades in memory-guided saccade showed a large effect and low heterogeneity (k = 11, n = 487; g = 0.86, 95% CI [0.64, 1.08], I² = 17.7%); and saccades during prolonged fixation evidenced large effect size and heterogeneity (k = 6, n = 325 g = 1.11, 95% CI [0.56, 1.65], I² = 79.1%) partially related to age. Among secondary outcomes, saccadic reaction time in AS (k = 22, n = 932, g = 0.34, 95% CI [0.06, 0.63], I² = 53.12%) and coefficient of variability in visually guided saccade (k = 5, n = 282, g = 0.53, 95% CI [0.28, 0.78], I² = 0.01%) indicated significant effects with small to moderate effects sizes.

CONCLUSIONS

ADHD groups commit more oculomotor inhibition failures than control groups. The substantial effects support the conclusion that oculomotor disinhibition is a relevant ADHD-related mechanism. Moderate effects observed in saccadic reaction time variability suggest that fluctuant performance in oculomotor tasks is another relevant characteristic of ADHD.

Effects of physical exercise in children with attention deficit/hyperactivity disorder

Attention deficit hyperactivity disorder (ADHD) is one of the most commonly neurodevelopmental disorders with a complex symptomatology in children, and frequently suffer from deficits in executive functions and motor abilities. Although medication-based treatments usually have a positive effect, possible side effects may result in a need for an adjunctive intervention. Present studies show positive effect of physical exercise on cognitive function. Therefore, the purpose of the current study is thoroughly examine the effects of physical exercise in children with ADHD. Preliminary evidence shows both acute and chronic physical exercise are beneficial to ADHD symptoms, executive function, and motor abilities. Benefits of acute exercise may gradually accumulate over time. Such benefits reflect the positive correlation between cognition and physical activity, and these benefits will also lead to changes in executive function after long-term training. Aerobic could induce to increase the neurotransmitter ie. serotonin, dopamine, brain-derived neurotrophic factor (BDNF) and brain blood flow. Perceptual motor and meditation could lead to neuroplasticity in nerve cells and synaptic connections; furthermore, strengthening the sensory-motor base contributes to the improvement of attention. An exercise program for children with ADHD include to moderate to high intensity interval training and cognitive tasks are suitable. The preliminary state of the evidence supports physical exercise as an adjunctive treatment for ADHD at this time.

Can auditory warning signals normalize eye movements in children with ADHD?

Attenuated baseline arousal has been hypothesized to underlie symptoms of attention deficit/hyperactivity disorder (ADHD). A behavioral signature of reduced baseline arousal is an increased beneficiary effect of warning signals in reaction tasks. This paradoxical effect is believed to be caused by a temporary increase in arousal induced by warning signals. In a preregistered study, we tested the hypothesis that children with high levels of ADHD symptoms would be hyperresponsive to warning signals in a well-established visual attention task (the gap/overlap paradigm). Previous studies using this task have found slower and more variable saccadic reaction times in children with ADHD compared to typically developing children, suggesting that these eye movement metrics are candidate biomarkers. We examined 71 children, of which 1/3 had a diagnosis of ADHD, using both dimensional analyses and group comparisons. Previously reported findings of reduced saccadic latency and increased latency variability were replicated. Importantly, saccadic latency was normalized by auditory warning signals. Analyses of pupil dilation, a physiological index of arousal and locus coeruleus-noradrenergic activity, confirmed that warning signals led to enhanced arousal. Our findings are novel and contribute to our understanding of arousal and attention in ADHD and have implications for treatment and interventions.

Saccade eye movement in children with attention deficit hyperactivity disorder

Objects: This study aims to investigate the saccade/anti-saccade eye movement in children with attention deficit/hyperactivity disorder (ADHD).Methods: Twelve children (8.8 ± 0.8 years) diagnosed with ADHD (DSM-V) and 12 control (9.1 ± 0.3 years) were invited to participate in the experiment where the iView Hi-SPEED eyetracker, with the sample rate at 500 Hz Binocular, was employed. The visual guided saccade (VGS) task was used to collect saccade latency and accuracy values. The anti-saccade task was used to collect saccade latency and accuracy values as well as the percentage of direction errors (PDE).Results: Children with ADHD showed a significant difference in latency in the 7.5° target and imprecision in both targets (7.5° and 15°) during the VGS task. Moreover, the ADHD group exhibited shorter latency (15° target) and significantly higher numbers in the Percentage of Direction Errors in the anti-saccade tasks than the control group.Conclusions: The results suggest that children with ADHD have the following difficulties: precise oculomotor control, oculomotor response inhibition function and basic visual attention.

Psychosocial stress affects the acquisition of cerebellar-dependent sensorimotor adaptation

Despite being overlooked in theoretical models of stress-related disorders, differences in cerebellar structure and function are consistently reported in studies of individuals exposed to current and early-life stressors. However, the mediating processes through which stress impacts upon cerebellar function are currently unknown. The aim of the current experiment was to test the effects of experimentally-induced acute stress on cerebellar functioning, using a classic, forward saccadic adaptation paradigm in healthy, young men and women. Stress induction was achieved by employing the Montreal Imaging Stress Task (MIST), a task employing mental arithmetic and negative social feedback to generate significant physiological and endocrine stress responses. Saccadic adaptation was elicited using the double-step target paradigm. In the experiment, 48 participants matched for gender and age were exposed to either a stress (n = 25) or a control (n = 23) condition. Saliva for cortisol analysis was collected before, immediately after, and 10, and 30 min after the MIST. Saccadic adaptation was assessed approximately 10 min after stress induction, when cortisol levels peaked. Participants in the stress group reported significantly more stress symptoms and exhibited greater total cortisol output compared to controls. The stress manipulation was associated with slower learning rates in the stress group, while control participants acquired adaptation faster. Learning rates were negatively associated with cortisol output and mood disturbance. Results suggest that experimentally-induced stress slowed acquisition of cerebellar-dependent saccadic adaptation, related to increases in cortisol output. These 'proof-of-principle' data demonstrate that stress modulates cerebellar-related functions.