Colour perception in ADHD

The efficacy of physical exercise interventions on mental health, cognitive function, and ADHD symptoms in children and adolescents with ADHD: an umbrella review

Background

A considerable number of published reviews have addressed the effects of physical exercise on mental health, cognitive function, or attention-deficit hyperactivity (ADHD) symptoms as outcomes in children and adolescents with ADHD. Their findings have often conflicted, therefore, there is an urgent need to synthesise a hierarchy of the evidence and examine the credibility of previous meta-analyses. To establish the robustness of these findings, we conducted an additional meta-analysis on a number of individual studies that were not covered in previous reviews but were suitable for inclusion in our own study.

Methods

Three reviewers independently searched Web of Science, Psych INFO, Embase, Cochrane Library, PubMed, SPORTDiscus, and Cumulative Index to Nursing and Allied Health Literature (CINAHL) for meta-analyses published between database inceptions to December 1, 2022. The individual studies were also screened from 1 January 2015 to 1 December 2022. We included meta-analyses and eligible individual studies that addressed the effects of exercise on at least one outcome of mental health, cognitive function, or ADHD symptoms in children and adolescents with ADHD. We excluded systematic reviews and articles that lacked sufficient data for a meaningful second analysis. The effect estimates (Hedges' g), 95% confidence interval (95% CI), 95% prediction interval (95% PI), small study effects, and excess significance bias were calculated. Finally, we categorised the meta-analyses based on the credibility of the evidence criteria and their quality using a Measurement Tool to Assess Systematic Reviews 2 checklist. This umbrella review was registered with PROSPERO, CRD42022361331.

Findings

Of 181 listed review articles and 60 individual papers, 10 reviews and 12 individual articles were included in the meta-analyses. This yielded 37 meta-analyses based on 106 study estimates. Evidence was highly suggestive for the effectiveness of exercise (class II) for improving inattention (G = 0.92, 95% CI: 0.44-1.39, 95%), inhibitory control (G = 0.82, 95% CI: 0.52-1.13), and cognitive flexibility (G = 0.52, 95% CI: 0.32-0.72). However, evidence for the effectiveness of exercise on emotional, social, and working memory outcomes was weak, and these results were not significant for hyperactivity and behavioural functioning.

Interpretation

Improvement of cognitive flexibility, inhibitory control, and inattention in children and adolescents with ADHD was highly suggested by exercise interventions. However, results were weak for other outcomes (emotional functioning, social functioning, and working memory). Further high-quality randomised controlled trials are, therefore, warranted to determine the effectiveness of exercise on weak outcomes.

Funding

None.

Association between ADHD and vision problems. A systematic review and meta-analysis

AIM

To conduct the first systematic review and meta-analysis assessing whether attention-deficit/hyperactivity disorder (ADHD) is associated with disorders of the eye, and/or altered measures of visual function.

METHOD

Based on a pre-registered protocol (PROSPERO: CRD42021256352), we searched PubMed, Web of Knowledge/Science, Ovid Medline, Embase and APA PsycINFO up to 16th November 2021, with no language/type of document restrictions. We included observational studies reporting at least one measure of vision in people of any age meeting DSM/ICD criteria for ADHD and in people without ADHD; or the prevalence of ADHD in people with and without vision disorders. Study quality was assessed with the Appraisal tool for Cross-Sectional Studies (AXIS). Random effects meta-analyses were used for data synthesis.

RESULTS

We included 42 studies in the narrative synthesis and 35 studies in the meta-analyses (3,250,905 participants). We found meta-analytic evidence of increased risk of astigmatism (OR = 1.79 [CI: 1.50, 2.14]), hyperopia and hypermetropia (OR = 1.79 [CI: 1.66, 1.94]), strabismus (OR = 1.93 [CI: 1.75, 2.12]), unspecified vision problems (OR = 1.94 [CI: 1.38, 2.73]) and reduced near point of convergence (OR = 5.02 [CI: 1.78, 14.11]); increased lag (Hedge's g = 0.63 [CI: 0.30, 0.96]) and variability (Hedge's g = 0.40 [CI: 0.17, 0.64]) of the accommodative response; and increased self-reported vision problems (Hedge's g = 0.63 [CI: 0.44, 0.82]) in people with ADHD compared to those without ADHD (with no significant heterogeneity). We also found meta-analytic evidence of no differences between people with and without ADHD on retinal nerve fiber layer thickness (Hedge's g = -0.19 [CI: -0.41, 0.02]) and refractive error (Hedge's g = 0.08 [CI: -0.26, 0.42]) (with no significant heterogeneity).

DISCUSSION

ADHD is associated with some self-reported and objectively ascertained functional vision problems, but not with structural alterations of the eye. Further studies should clarify the causal relationship, if any, between ADHD and problems of vision.

TRIAL REGISTRATION

PROSPERO registration: CRD42021256352.

Understanding ADHD: Toward an Innovative Therapeutic Intervention

Attention deficit hyperactivity disorder (ADHD) is a pervasive condition affecting persons across all age groups, although it is primarily diagnosed in children. This neurological condition affects behavior, learning, and social adjustment and requires specific symptomatic criteria to be fulfilled for diagnosis. ADHD may be treated with a combination of psychological or psychiatric therapeutic interventions, but it often goes unattended. People with ADHD face societal bias challenges that impact how they manage the disorder and how they view themselves. This paper summarizes the present state of understanding of this disorder, with particular attention to early diagnosis and innovative therapeutic intervention. Contemporary understanding of the mind-brain duality allows for innovative therapeutic interventions based on neurological stimulation. This paper introduces the concept of neurostimulation as a therapeutic intervention for ADHD and poses the question of the relationship between patient adherence to self-administered therapy and the aesthetic design features of the neurostimulation device. By fabricating devices that go beyond safety and efficacy to embrace the aesthetic preferences of the patient, it is proposed that there will be improvements in patient adherence to a device intended to address ADHD.

ADHD: Current Concepts and Treatments in Children and Adolescents

Attention deficit hyperactivity disorder (ADHD) is among the most frequent disorders within child and adolescent psychiatry, with a prevalence of over 5%. Nosological systems, such as the Diagnostic and Statistical Manual of Mental Disorders, 5th edition (DSM-5) and the International Classification of Diseases, editions 10 and 11 (ICD-10/11) continue to define ADHD according to behavioral criteria, based on observation and on informant reports. Despite an overwhelming body of research on ADHD over the last 10 to 20 years, valid neurobiological markers or other objective criteria that may lead to unequivocal diagnostic classification are still lacking. On the contrary, the concept of ADHD seems to have become broader and more heterogeneous. Thus, the diagnosis and treatment of ADHD are still challenging for clinicians, necessitating increased reliance on their expertise and experience. The first part of this review presents an overview of the current definitions of the disorder (DSM-5, ICD-10/11). Furthermore, it discusses more controversial aspects of the construct of ADHD, including the dimensional versus categorical approach, alternative ADHD constructs, and aspects pertaining to epidemiology and prevalence. The second part focuses on comorbidities, on the difficulty of distinguishing between "primary" and "secondary" ADHD for purposes of differential diagnosis, and on clinical diagnostic procedures. In the third and most prominent part, an overview of current neurobiological concepts of ADHD is given, including neuropsychological and neurophysiological researches and summaries of current neuroimaging and genetic studies. Finally, treatment options are reviewed, including a discussion of multimodal, pharmacological, and nonpharmacological interventions and their evidence base.

Ocular findings in patients with attention deficit and hyperactivity

AIM

To evaluate ocular findings, contrast sensitivity, color perception, and macular and retinal nerve fiber layer (RNFL) thickness in patients with attention-deficit/hyperactivity disorder (ADHD).

MATERIALS AND METHODS

This prospective study included a group of 37 patients aged 6-16 years diagnosed with combined ADHD and a healthy control group of 37 children. The participants underwent an ophthalmological examination. Color vision testing was administered using the Ishihara plates test. Contrast sensitivity test was performed using the Functional Acuity Contrast Test. Macular thickness and RNFL thickness were measured by spectral-domain optical coherence tomography.

RESULTS

No significant difference was found between the patient and control groups with regard to ocular findings, color vision, and convergence insufficiency (p > 0.05). Contrast sensitivity level was significantly lower at four out of five spatial frequencies (1.5, 3, 12, and 18 cpd) in the patient group compared to the control group. The RNFL thickness in nasal quadrant and macular thickness was significantly higher in the healthy control group compared to the ADHD group.

CONCLUSION

Contrast sensitivity levels and the nasal quadrant RNFL thickness were significantly lower in the patient group compared to the control group. Based on the findings of the study, we suggest that the level of contrast in the tools used by ADHD patients in daily life settings should be enhanced.

Attentional blink and putative noninvasive dopamine markers: Two experiments to consolidate possible associations

Adaptive behavioral control involves a balance between top-down persistence and flexible updating of goals under changing demands. According to the metacontrol state model (MSM), this balance emerges from the interaction between the frontal and the striatal dopaminergic system. The attentional blink (AB) task has been argued to tap into the interaction between persistence and flexibility, as it reflects overpersistence—the too-exclusive allocation of attentional resources to the processing of the first of two consecutive targets. Notably, previous studies are inconclusive about the association between the AB and noninvasive proxies of dopamine including the spontaneous eye blink rate (sEBR), which allegedly assesses striatal dopamine levels. We aimed to substantiate and extend previous attempts to predict individual sizes of the AB in two separate experiments with larger sample sizes (N = 71 & N = 65) by means of noninvasive behavioral and physiological proxies of dopamine (DA), such as sEBR and mood measures, which are likely to reflect striatal dopamine levels, and color discrimination, which has been argued to tap into the frontal dopamine levels. Our findings did not confirm the prediction that AB size covaries with sEBR, mood, or color discrimination. The implications of this inconsistency with previous observations are discussed.

Phonological Working Memory Deficits in ADHD Revisited: The Role of Lower Level Information-Processing Deficits in Impaired Working Memory Performance

OBJECTIVE

The current study dissociates lower level information-processing abilities (visual registration/encoding, visual-to-phonological conversion, and response output) and examines their contribution to ADHD-related phonological working memory (PHWM) deficits.

METHOD

Twenty children with ADHD and 15 typically developing (TD) children completed tasks assessing PHWM, visual registration/encoding, visual-to-phonological conversion, and response output.

RESULTS

Relative to TD children, children with ADHD exhibited deficient visual registration/encoding ( d = 0.60), visual-to-phonological conversion ( d = 0.56), and PHWM ( d = 0.72) but faster response output ( d = -0.66). Bias-corrected, bootstrapped mediation analyses revealed that visual registration/encoding, but not visual-to-phonological conversion, partially mediated ADHD-related PHWM impairments. In contrast, faster response output in children with ADHD served as a suppressor variable, such that greater PHWM deficits were observed in children with ADHD after controlling for their faster response output ( d = 0.72 vs. 0.85).

CONCLUSION

Results implicate both lower level (visual registration/encoding) and higher order (PHWM) impairments in ADHD. Implications for designing educationally relevant cognitive interventions are discussed.

Neural processing of working memory in adults with ADHD in a visuospatial change detection task with distractors

Individuals with Attention-Deficit Hyperactivity Disorder (ADHD) are often characterized by deficits in working memory (WM), which manifest in academic, professional, and mental health difficulties. To better understand the underlying mechanisms of these presumed WM deficits, we compared adults with ADHD to their peers on behavioral and neural indices of WM. We used a visuospatial change detection task with distractors which was designed to assess the brain’s ability to effectively filter out distractors from WM, in addition to testing for effects of WM load. Twenty-seven unmedicated adults with ADHD were compared to 27 matched peers on event-related potential (ERP) measures of WM, i.e., the contralateral delay activity (CDA). Despite severe impairments in everyday life functioning, findings showed no difference in deficits in behavioral tests of working memory for adults with ADHD compared to their peers. Interestingly, there were differences in neural activity between individuals with ADHD and their peers showing that the CDA of individuals with ADHD did not distinguish between high, distractor, and low memory load conditions. These data suggest, in the face of comparable behavioral performance, a difference in neural processing efficiency, wherein the brains of individuals with ADHD may not be as selective in the allocation of neural resources to perform a WM task.

Colour discrimination thresholds in type 1 Bipolar Disorder: a pilot study

Although some studies have reported perceptual changes in psychosis, no definitive conclusions have been drawn about visual disturbances that are related to bipolar disorder (BPD). The purpose of the present study was to evaluate colour vision in BPD patients. Data were recorded from 24 participants: healthy control group (n = 12) and type 1 BPD group (n = 12). The participants were 20-45 years old and they were free from neurological disorders and identifiable ocular disease and had normal or corrected-to-normal visual acuity. Colour discrimination was evaluated using the Lanthony D-15d, Trivector and Ellipse tests, using a psychophysical forced-choice method. The relationship of visual measures to mood state and cognitive function was also investigated. The results showed that BPD patients had higher colour discrimination thresholds in the D15d (p < 0.001), Trivector (p < 0.001) and Ellipse (p < 0.01) tests compared with healthy controls. Linear regression analysis showed that mood state was related to colour discrimination. BPD individuals were not impaired in cognitive tasks. The present study provided new evidence of potential links between type 1 BPD and visual processing impairments. This research suggests a new direction for studies and the need for research in this field of study.

Color vision predicts processing modes of goal activation during action cascading

One of the most important functions of cognitive control is action cascading: the ability to cope with multiple response options when confronted with various task goals. A recent study implicates a key role for dopamine (DA) in this process, suggesting higher D1 efficiency shifts the action cascading strategy toward a more serial processing mode, whereas higher D2 efficiency promotes a shift in the opposite direction by inducing a more parallel processing mode (Stock, Arning, Epplen, & Beste, 2014). Given that DA is found in high concentration in the retina and modulation of retinal DA release displays characteristics of D2-receptors (Peters, Schweibold, Przuntek, & Müller, 2000), color vision discrimination might serve as an index of D2 efficiency. We used color discrimination, assessed with the Lanthony Desaturated Panel D-15 test, to predict individual differences (N = 85) in a stop-change paradigm that provides a well-established measure of action cascading. In this task it is possible to calculate an individual slope value for each participant that estimates the degree of overlap in task goal activation. When the stopping process of a previous task goal has not finished at the time the change process toward a new task goal is initiated (parallel processing), the slope value becomes steeper. In case of less overlap (more serial processing), the slope value becomes flatter. As expected, participants showing better color vision were more prone to activate goals in a parallel manner as indicated by a steeper slope. Our findings suggest that color vision might represent a predictor of D2 efficiency and the predisposed processing mode of goal activation during action cascading.

Color Vision Losses in Autism Spectrum Disorders

Autism spectrum disorders (ASDs) are neurodevelopmental conditions characterized by impairments in social/communication abilities and restricted behaviors. The present study aims to examine color vision discrimination in ASD children and adolescents without intellectual disability. The participants were also subdivided in order to compare color vision thresholds of autistic participants and those who achieved diagnostic criteria for Asperger Syndrome (AS). Nine subjects with autism, 11 participants with AS and 36 typically developing children and adolescents participated in the study. Color vision was assessed by the Cambridge Color Test (CCT). The Trivector protocol was administered to determine color discrimination thresholds along the protan, deutan, and tritan color confusion lines. Data from ASD participants were compared to tolerance limits for 90% of the population with 90% probability obtained from controls thresholds. Of the 20 ASD individuals examined, 6 (30%) showed color vision losses. Elevated color discrimination thresholds were found in 3/9 participants with autism and in 3/11 AS participants. Diffuse and tritan deficits were found. Mechanisms for chromatic losses may be either at the retinal level and/or reflect reduced cortical integration.

Revisiting the co-existence of Attention-Deficit/Hyperactivity Disorder and Chronic Tic Disorder in childhood-The case of colour discrimination, sustained attention and interference control

Objective

Attention Deficit / Hyperactivity Disorder (ADHD) and Chronic Tic Disorder (CTD) are two common and frequently co-existing disorders, probably following an additive model. But this is not yet clear for the basic sensory function of colour processing sensitive to dopaminergic functioning in the retina and higher cognitive functions like attention and interference control. The latter two reflect important aspects for psychoeducation and behavioural treatment approaches.

Methods

Colour discrimination using the Farnsworth-Munsell 100-hue Test, sustained attention during the Frankfurt Attention Inventory (FAIR), and interference liability during Colour- and Counting-Stroop-Tests were assessed to further clarify the cognitive profile of the co-existence of ADHD and CTD. Altogether 69 children were classified into four groups: ADHD (N = 14), CTD (N = 20), ADHD+CTD (N = 20) and healthy Controls (N = 15) and compared in cognitive functioning in a 2×2-factorial statistical model.

Results

Difficulties with colour discrimination were associated with both ADHD and CTD factors following an additive model, but in ADHD these difficulties tended to be more pronounced on the blue-yellow axis. Attention problems were characteristic for ADHD but not CTD. Interference load was significant in both Colour- and Counting-Stroop-Tests and unrelated to colour discrimination. Compared to Controls, interference load in the Colour-Stroop was higher in pure ADHD and in pure CTD, but not in ADHD+CTD, following a sub-additive model. In contrast, interference load in the Counting-Stroop did not reveal ADHD or CTD effects.

Conclusion

The co-existence of ADHD and CTD is characterized by additive as well as sub-additive performance impairments, suggesting that their co-existence may show simple additive characteristics of both disorders or a more complex interaction, depending on demand. The equivocal findings on interference control may indicate limited validity of the Stroop-Paradigm for clinical assessments.

Perception in attention deficit hyperactivity disorder

A large body of research demonstrated that individuals with attention deficit hyperactivity disorder (ADHD) suffer from various neuropsychological deficits. In contrast, less is known and only divergent evidence exists on perceptual functions of individuals with ADHD. This is problematic as neuropsychological and perceptual functions are closely interrelated and are often difficult to disentangle in behavioral assessments. This study presents the conduct and results of a systematic literature review on perceptual functions in children and adults with ADHD. This review considers studies using psychophysical methods (objective measurements) and self- and informant reports (subjective measurements). Results indicate that individuals with ADHD have altered perceptual functions in various domains as compared to typically developing individuals. Increased perceptual functions in individuals with ADHD were found with regard to olfactory detection thresholds, whereas reduced perceptual functions were evident for aspects of visual and speech perception. Moreover, individuals with ADHD were found to experience discomfort to sensory stimuli at a lower level than typically developing individuals. Alterations of perceptual functions in individuals with ADHD were shown to be moderated by various factors, such as pharmacological treatment, cognitive functions, and symptom severity. We conclude by giving implications for daily life functioning and clinical practice.

Desempenho do processamento fonológico, leitura e escrita em escolares com transtorno de déficit de atenção e hiperatividade

RESUMO Objetivo: comparar o desempenho do processamento fonológico, da leitura e escrita de palavras reais e inventadas entre os escolares com transtorno de déficit de atenção e hiperatividade e escolares com bom desempenho escolar. Métodos: participaram deste estudo 30 escolares, na faixa etária de 9 a 12 anos, de ambos os gêneros, do Ensino Fundamental de escolas públicas e particulares, divididos em: Grupo Experimental (15 escolares com diagnóstico interdisciplinar de transtorno de déficit de atenção e hiperatividade) e Grupo Controle (15 escolares com bom desempenho escolar), pareado com o Grupo Experimental em idade, gênero, escolaridade, tipo de instituição de ensino (pública e particular). Os instrumentos utilizados para avaliação foram: Instrumento de Avaliação Sequencial (CONFIAS), Teste de Nomeação Seriada Rápida (RAN), Prova de repetição de palavras sem significado e Prova de leitura e escrita. Os resultados foram analisados por meio de testes estatísticos (Mann Whitney e Teste t de Student), adotando-se nível de significância de 5% (0,05). Resultados: os resultados analisados por meio de testes estatísticos revelaram diferenças significantes entre o grupo experimental e o grupo controle nas provas avaliadas. Conclusão: escolares com transtorno de déficit de atenção e hiperatividade apresentaram desempenho inferior em habilidades de consciência fonológica, acesso ao léxico, memória operacional, leitura e escrita de palavras, quando comparados aos escolares sem transtorno de déficit de atenção e hiperatividade, com bom desempenho escolar.

A 3D learning playground for potential attention training in ADHD: A brain computer interface approach

This paper presents a novel brain-computer-interface (BCI) system that could potentially be used for enhancing the attention ability of subjects with attention deficit hyperactivity disorder (ADHD). It employs the steady state visual evoked potential (SSVEP) paradigm. The developed system consists of a 3D classroom environment with active 3D distractions and 2D games executed on the blackboard. The system is concealed as a game (with stages of varying difficulty) with an underlying story to motivate the subjects. It was tested on eleven healthy subjects and the results undeniably establish that by moving to a higher stage in the game where the 2D environment is changed to 3D along with the added 3D distractions, the difficulty level in keeping attention on the main task increases for the subjects. Results also show a mean accuracy of 92.26 ± 7.97% and a mean average selection time of 3.07 ± 1.09 seconds.

Color Vision Deficiency and Functional Disorders Among Israeli Male Adolescents Between 2007 and 2013

Color vision deficiency has been associated with educational difficulties among male children, as well as attention-deficit hyperactivity disorder (ADHD). We examined the association of color vision deficiency with functional conditions, including ADHD, irritable bowel syndrome, enuresis and somatoform disorders, in a large population of male adolescents. We included all Israeli male adolescents that underwent medical and cognitive examinations during conscription between the years 2007 and 2013. The prevalence of ADHD, irritable bowel syndrome, enuresis, and somatoform disorders among color vision deficiency patients was compared to a control group. The study included 305 964 males aging 17 ± 0.6, of which 7584 (2.5%) had color vision deficiency. Using a multivariable analysis, the probability for irritable bowel syndrome, enuresis, and somatoform disorders among color vision deficiency patients was increased by 1.41, 1.94, and 3.87, respectively (P < .05). No significant association was found between ADHD and color vision deficiency. Color vision abnormalities are associated with functional disorders in male adolescents, including irritable bowel syndrome, enuresis, and somatoform disorders.

VI. The role of physical activity in reducing barriers to learning in children with developmental disorders

Emerging research suggests that physical activity may be an effective non-pharmaceutical intervention approach for childhood developmental disorders. Findings indicate that both single bouts of activity and chronic physical activity associate with improved mental health and classroom performance in children with attention-deficit/hyperactivity disorder and children with autism spectrum disorders. This review describes the research in this area and identifies limitations and challenges to the translation of these findings to promote physical activity in clinical practice and educational policy.

Color vision in attention-deficit/hyperactivity disorder: a pilot visual evoked potential study

BACKGROUND

Individuals with attention-deficit/hyperactivity disorder (ADHD) are reported to manifest visual problems (including ophthalmological and color perception, particularly for blue-yellow stimuli), but findings are inconsistent. Accordingly, this study investigated visual function and color perception in adolescents with ADHD using color Visual Evoked Potentials (cVEP), which provides an objective measure of color perception.

METHOD

Thirty-one adolescents (aged 13-18), 16 with a confirmed diagnosis of ADHD, and 15 healthy peers, matched for age, gender, and IQ participated in the study. All underwent an ophthalmological exam, as well as electrophysiological testing color Visual Evoked Potentials (cVEP), which measured the latency and amplitude of the neural P1 response to chromatic (blue-yellow, red-green) and achromatic stimuli.

RESULT

No intergroup differences were found in the ophthalmological exam. However, significantly larger P1 amplitude was found for blue and yellow stimuli, but not red/green or achromatic stimuli, in the ADHD group (particularly in the medicated group) compared to controls.

CONCLUSION

Larger amplitude in the P1 component for blue-yellow in the ADHD group compared to controls may account for the lack of difference in color perception tasks. We speculate that the larger amplitude for blue-yellow stimuli in early sensory processing (P1) might reflect a compensatory strategy for underlying problems including compromised retinal input of s-cones due to hypo-dopaminergic tone.

Colour vision in ADHD: part 1--testing the retinal dopaminergic hypothesis

OBJECTIVES

To test the retinal dopaminergic hypothesis, which posits deficient blue color perception in ADHD, resulting from hypofunctioning CNS and retinal dopamine, to which blue cones are exquisitely sensitive. Also, purported sex differences in red color perception were explored.

METHODS

30 young adults diagnosed with ADHD and 30 healthy young adults, matched on age and gender, performed a psychophysical task to measure blue and red color saturation and contrast discrimination ability. Visual function measures, such as the Visual Activities Questionnaire (VAQ) and Farnsworth-Munsell 100 hue test (FMT), were also administered.

RESULTS

Females with ADHD were less accurate in discriminating blue and red color saturation relative to controls but did not differ in contrast sensitivity. Female control participants were better at discriminating red saturation than males, but no sex difference was present within the ADHD group.

CONCLUSION

Poorer discrimination of red as well as blue color saturation in the female ADHD group may be partly attributable to a hypo-dopaminergic state in the retina, given that color perception (blue-yellow and red-green) is based on input from S-cones (short wavelength cone system) early in the visual pathway. The origin of female superiority in red perception may be rooted in sex-specific functional specialization in hunter-gather societies. The absence of this sexual dimorphism for red colour perception in ADHD females warrants further investigation.

Color vision in ADHD: part 2--does attention influence color perception?

Background

To investigate the impact of exogenous covert attention on chromatic (blue and red) and achromatic visual perception in adults with and without Attention Deficit Hyperactivity Disorder (ADHD). Exogenous covert attention, which is a transient, automatic, stimulus-driven form of attention, is a key mechanism for selecting relevant information in visual arrays.

Methods

30 adults diagnosed with ADHD and 30 healthy adults, matched on age and gender, performed a psychophysical task designed to measure the effects of exogenous covert attention on perceived color saturation (blue, red) and contrast sensitivity.

Results

The effects of exogenous covert attention on perceived blue and red saturation levels and contrast sensitivity were similar in both groups, with no differences between males and females. Specifically, exogenous covert attention enhanced the perception of blue saturation and contrast sensitivity, but it had no effect on the perception of red saturation.

Conclusion

The findings suggest that exogenous covert attention is intact in adults with ADHD and does not account for the observed impairments in the perception of chromatic (blue and red) saturation.

Electronic supplementary material

The online version of this article (doi:10.1186/1744-9081-10-39) contains supplementary material, which is available to authorized users.

Visual function and color vision in adults with Attention-Deficit/Hyperactivity Disorder

PURPOSE

Color vision and self-reported visual function in everyday life in young adults with Attention-Deficit/Hyperactivity Disorder (ADHD) were investigated.

METHOD

Participants were 30 young adults with ADHD and 30 controls matched for age and gender. They were tested individually and completed the Visual Activities Questionnaire (VAQ), Farnsworth-Munsell 100 Hue Test (FMT) and A Quick Test of Cognitive Speed (AQT).

RESULTS

The ADHD group reported significantly more problems in 4 of 8 areas on the VAQ: depth perception, peripheral vision, visual search and visual processing speed. Further analyses of VAQ items revealed that the ADHD group endorsed more visual problems associated with driving than controls. Color perception difficulties on the FMT were restricted to the blue spectrum in the ADHD group. FMT and AQT results revealed slower processing of visual stimuli in the ADHD group.

CONCLUSION

A comprehensive investigation of mechanisms underlying visual function and color vision in adults with ADHD is warranted, along with the potential impact of these visual problems on driving performance.

A comparison of phenylketonuria with attention deficit hyperactivity disorder: do markedly different aetiologies deliver common phenotypes?

Phenylketonuria (PKU) is a well-defined metabolic disorder arising from a mutation that disrupts phenylalanine metabolism and so produces a variety of neural changes indirectly. Severe cognitive impairment can be prevented by dietary treatment; however, residual symptoms may be reported. These residual symptoms appear to overlap a more prevalent childhood disorder: Attention Deficit/Hyperactivity Disorder (ADHD). However, the aetiology of ADHD is a vast contrast to PKU: it seems to arise from a complex combination of genes; and it has a substantial environmental component. We ask whether these two disorders result from two vastly different genotypes that converge on a specific core phenotype that includes similar dysfunctions of Gray's (Gray, 1982) Behavioural Inhibition System (BIS), coupled with other disorder-specific dysfunctions. If so, we believe comparison of the commonalities will allow greater understanding of the neuropsychology of both disorders. We review in detail the aetiology, treatment, neural pathology, cognitive deficits and electrophysiological abnormalities of PKU; and compare this with selected directly matching aspects of ADHD. The biochemical and neural pathologies of PKU and ADHD are quite distinct in their causes and detail; but they result in the disorder in the brain of large amino acid levels, dopamine and white matter that are very similar and could explain the overlap of symptoms within and between the PKU and ADHD spectra. The common deficits affect visual function, motor function, attention, working memory, planning, and inhibition. For each of PKU and ADHD separately, a subset of deficits has been attributed to a primary dysfunction of behavioural inhibition. In the case of ADHD (excluding the inattentive subtype) this has been proposed to involve a specific failure of the BIS; and we suggest that this is also true of PKU. This accounts for a substantial proportion of the parallels in the superficial symptoms of both disorders and we see this as linked to prefrontal, rather than more general, dysfunction of the BIS.

Colour discrimination and categorisation in Williams syndrome

Individuals with Williams syndrome (WS) present with impaired functioning of the dorsal visual stream relative to the ventral visual stream. As such, little attention has been given to ventral stream functions in WS. We investigated colour processing, a predominantly ventral stream function, for the first time in nineteen individuals with Williams syndrome. Colour discrimination was assessed using the Farnsworth-Munsell 100 hue test. Colour categorisation was assessed using a match-to-sample test and a colour naming task. A visual search task was also included as a measure of sensitivity to the size of perceptual colour difference. Results showed that individuals with WS have reduced colour discrimination relative to typically developing participants matched for chronological age; performance was commensurate with a typically developing group matched for non-verbal ability. In contrast, categorisation was typical in WS, although there was some evidence that sensitivity to the size of perceptual colour differences was reduced in this group.

Omega-3 fatty acids are related to abnormal emotion processing in adolescent boys with attention deficit hyperactivity disorder

BACKGROUND

In addition to the core symptoms, attention deficit hyperactivity disorder (ADHD) is associated with poor emotion regulation. There is some evidence that children and young adults with ADHD have lower omega-3 levels and that supplementation with omega-3 can improve both ADHD and affective symptoms. We therefore investigated differences between ADHD and non-ADHD children in omega-3/6 fatty acid plasma levels and the relationship between those indices and emotion-elicited event-related potentials (ERPs).

METHODS

Children/adolescents with (n=31) and without ADHD (n=32) were compared in their plasma omega-3/6 indices and corresponding ERPs during an emotion processing task.

RESULTS

Children with ADHD had lower mean omega-3/6 and ERP abnormalities in emotion processing, independent of emotional valence relative to control children. ERP abnormalities were significantly associated with lower omega-3 levels in the ADHD group.

CONCLUSIONS

The findings reveal for the first time that lower omega-3 fatty acids are associated with impaired emotion processing in ADHD children.

Interference control in adult ADHD: no evidence for interference control deficits if response speed is controlled by delta plots

Several theoretical accounts assume that interference control deficits belong to the core symptoms of adult ADHD. However, findings of increased interference effects in adult ADHD patients compared with healthy adults may be confounded with the simultaneous finding of generally slower responses in the patient group. The current study compared the magnitude of the interference effect in the Stroop task between a group of adults with ADHD and a healthy adult control group in a procedure that accounted for differences in overall response speed by using delta plots. The amount of interference did not differ between patient and control group at comparable reaction time levels. These results challenge the conclusions of the previous studies, in that they indicate that interference control is not impaired in adult ADHD.

Exercise improves behavioral, neurocognitive, and scholastic performance in children with attention-deficit/hyperactivity disorder

OBJECTIVE

To examine the effect of a single bout of moderate-intensity aerobic exercise on preadolescent children with attention-deficit/hyperactivity disorder (ADHD) using objective measures of attention, brain neurophysiology, and academic performance.

STUDY DESIGN

Using a within-participants design, task performance and event-related brain potentials were assessed while participants performed an attentional-control task following a bout of exercise or seated reading during 2 separate, counterbalanced sessions.

RESULTS

Following a single 20-minute bout of exercise, both children with ADHD and healthy match control children exhibited greater response accuracy and stimulus-related processing, with the children with ADHD also exhibiting selective enhancements in regulatory processes, compared with after a similar duration of seated reading. In addition, greater performance in the areas of reading and arithmetic were observed following exercise in both groups.

CONCLUSION

These findings indicate that single bouts of moderately intense aerobic exercise may have positive implications for aspects of neurocognitive function and inhibitory control in children with ADHD.

Serum epidermal growth factor predicts cognitive functions in early, drug-naive Parkinson's disease patients

Epidermal growth factor (EGF) has been proposed as a candidate biomarker for cognitive impairment in Parkinson's disease (PD). We aimed to assess the relationship between serum EGF and cognitive functions in early, drug-naive PD patients and evaluate the predictive value of EGF on cognitive functions in a 2-year follow-up study. Serum EGF was measured in 65 early, drug-naive PD patients, that underwent a comprehensive neuropsychological battery. Motor symptoms were assessed by means of the Unified Parkinson's Disease Rating Scale, Part III (UPDRS-III). Neuropsychological evaluation was repeated after 2 years. Spearman's rank correlation was used to assess the relationship between serum EGF levels and neuropsychological variables. Linear regression analysis was used to evaluate the relationship between EGF and neuropsychological scores as well as other variables (age, gender, UPDRS-III, levodopa equivalent dose, and type of treatment at follow-up) potentially affecting cognitive performance. Variation over time in cognitive scores was analyzed using repeated-measures ANOVA. At baseline, EGF was the only significant variable associated with performance on semantic fluency (R (2) = 0.131; p = 0.005). EGF levels (p = 0.025), together with UPDRS-III (p = 0.009) and age (p = 0.011), were associated with performance on frontal assessment battery (R (2) = 0.260). At 2-year follow-up, EGF was the only significant variable to predict performance on semantic fluency (R (2) = 0.147; p = 0.025) and color naming task of Stroop color-word test (R (2) = 0.121; p = 0.044). Serum EGF levels are related to frontal and temporal cognitive functions in early, drug-naive PD patients and predict performance on frontal and posterior cognitive functions at 2-year follow-up. EGF is proposed as a potential serum biomarker for early cognitive impairment in PD.

Virtual environment to quantify the influence of colour stimuli on the performance of tasks requiring attention

Background

Recent studies indicate that the blue-yellow colour discrimination is impaired in ADHD individuals. However, the relationship between colour and performance has not been investigated. This paper describes the development and the testing of a virtual environment that is capable to quantify the influence of red-green versus blue-yellow colour stimuli on the performance of people in a fun and interactive way, being appropriate for the target audience.

Methods

An interactive computer game based on virtual reality was developed to evaluate the performance of the players.

The game's storyline was based on the story of an old pirate who runs across islands and dangerous seas in search of a lost treasure. Within the game, the player must find and interpret the hints scattered in different scenarios. Two versions of this game were implemented. In the first, hints and information boards were painted using red and green colours. In the second version, these objects were painted using blue and yellow colours. For modelling, texturing, and animating virtual characters and objects the three-dimensional computer graphics tool Blender 3D was used. The textures were created with the GIMP editor to provide visual effects increasing the realism and immersion of the players. The games were tested on 20 non-ADHD volunteers who were divided into two subgroups (A1 and A2) and 20 volunteers with ADHD who were divided into subgroups B1 and B2. Subgroups A1 and B1 used the first version of the game with the hints painted in green-red colors, and subgroups A2 and B2 the second version using the same hints now painted in blue-yellow. The time spent to complete each task of the game was measured.

Results

Data analyzed with ANOVA two-way and posthoc TUKEY LSD showed that the use of blue/yellow instead of green/red colors decreased the game performance of all participants. However, a greater decrease in performance could be observed with ADHD participants where tasks, that require attention, were most affected.

Conclusions

The game proved to be a user-friendly tool capable to detect and quantify the influence of color on the performance of people executing tasks that require attention and showed to be attractive for people with ADHD.

A review of fronto-striatal and fronto-cortical brain abnormalities in children and adults with Attention Deficit Hyperactivity Disorder (ADHD) and new evidence for dysfunction in adults with ADHD during motivation and attention

Attention Deficit Hyperactivity Disorder (ADHD) has long been associated with abnormalities in frontal brain regions. In this paper we review the current structural and functional imaging evidence for abnormalities in children and adults with ADHD in fronto-striatal, fronto-parieto-temporal, fronto-cerebellar and fronto-limbic regions and networks. While the imaging studies in children with ADHD are more numerous and consistent, an increasing number of studies suggests that these structural and functional abnormalities in fronto-cortical and fronto-subcortical networks persist into adulthood, despite a relative symptomatic improvement in the adult form of the disorder. We furthermore present new data that support the notion of a persistence of neurofunctional deficits in adults with ADHD during attention and motivation functions. We show that a group of medication-naïve young adults with ADHD behaviours who were followed up 20 years from a childhood ADHD diagnosis show dysfunctions in lateral fronto-striato-parietal regions relative to controls during sustained attention, as well as in ventromedial orbitofrontal regions during reward, suggesting dysfunctions in cognitive-attentional as well as motivational neural networks. The lateral fronto-striatal deficit findings, furthermore, were strikingly similar to those we have previously observed in children with ADHD during the same task, reinforcing the notion of persistence of fronto-striatal dysfunctions in adult ADHD. The ventromedial orbitofrontal deficits, however, were associated with comorbid conduct disorder (CD), highlighting the potential confound of comorbid antisocial conditions on paralimbic brain deficits in ADHD. Our review supported by the new data therefore suggest that both adult and childhood ADHD are associated with brain abnormalities in fronto-cortical and fronto-subcortical systems that mediate the control of cognition and motivation. The brain deficits in ADHD therefore appear to be multi-systemic and to persist throughout the lifespan.

Impact of sleep restriction on neurobehavioral functioning of children with attention deficit hyperactivity disorder

STUDY OBJECTIVES

The objective of this study was to assess the cumulative impact of 1 hour of nightly sleep restriction over the course of 6 nights on the neurobehavioral functioning (NBF) of children with attention deficit hyperactivity disorder (ADHD) and healthy controls.

DESIGN

Following 6 nights of actigraphic monitoring of sleep to determine baseline sleep duration, children were asked to restrict sleep duration by 1 hour for 6 consecutive nights. NBF was assessed at baseline (Day 6) and following sleep manipulation (Day 12).

SETTING

A quiet location within their home environments.

PARTICIPANTS

Forty-three children (11 ADHD, 32 Controls, mean age = 8.7 years, SD = 1.3) between the ages of 7 and 11 years.

INTERVENTIONS

NA.

MEASUREMENTS

Sleep was monitored using actigraphy. In addition, parents were asked to complete nightly sleep logs. Sleepiness was evaluated using a questionnaire. The Conners' Continuous Performance Test (CPT) was used to assess NBF.

RESULTS

Restricted sleep led to poorer CPT scores on two-thirds of CPT outcome measures in both healthy controls and children with ADHD. The performance of children with ADHD following sleep restriction deteriorated from subclinical levels to the clinical range of inattention on two-thirds of CPT outcome measures.

CONCLUSIONS

Moderate sleep restriction leads to a detectable negative impact on the NBF of children with ADHD and healthy controls, leading to a clinical level of impairment in children with ADHD.

Lexical and grammatical development in a child with cochlear implant and attention deficit: A case study

This is the first study to explore lexical and grammatical development in a deaf child diagnosed with Attention Deficit Hyperactivity Disorder, Inattentive sub-type (ADHD/I). The child, whose family language was Spanish, was fitted with a cochlear implant (CI) when she was 18 months old. ADHD/I, for which she was prescribed medication, was diagnosed 3;6 years later. Speech samples were videotaped over the first 4 years of CI use and during a follow-up session 1 year later. Samples were transcribed according to CHAT conventions and several measures of expressive language were obtained. Receptive language was evaluated with standardized tests. Results show that while some aspects of her development seemed relatively positive (e.g., acquisition of verbal morphemes at the same auditory age as typical children), other characteristics were atypical for a CI user: (1) preference for paralexical expressions in early lexicon; (2) lexical errors in colours and other abstract words; and (3) low MLU and varied grammatical errors including disorganized discourse. Medication had a positive effect on all these characteristics, providing evidence of a link with ADHD/I. This study concludes that ADHD/I had a direct impact on the lexical and grammatical development in this child, as well as an indirect influence over her communicative style. More studies are needed to explore language characteristics of children with CI and ADHD.

Beyond the dual pathway model: evidence for the dissociation of timing, inhibitory, and delay-related impairments in attention-deficit/hyperactivity disorder

OBJECTIVE

The dual pathway model explains neuro-psychological heterogeneity in Attention Deficit/Hyperactivity Disorder (ADHD) in terms of dissociable cognitive and motivational deficits each affecting some but not other patients. We explore whether deficits in temporal processing might constitute a third dissociable neuropsychological component of ADHD.

METHOD

Nine tasks designed to tap three domains (inhibitory control, delay aversion and temporal processing) were administered to ADHD probands (n=71; ages 6 to 17 years), their siblings (n=71; 65 unaffected by ADHD) and a group of non-ADHD controls (n=50). IQ and working memory were measured.

RESULTS

Temporal processing, inhibitory control and delay-related deficits represented independent neuropsychological components. ADHD children differed from controls on all factors. For ADHD patients, the co-occurrence of inhibitory, temporal processing and delay-related deficits was no greater than expected by chance with substantial groups of patients showing only one problem. Domain-specific patterns of familial co-segregation provided evidence for the validity of neuropsychological subgroupings.

CONCLUSION

The current results illustrate the neuropsychological heterogeneity in ADHD and initial support for a triple pathway model. The findings need to be replicated in larger samples.

Vision in autism spectrum disorders

Autism spectrum disorders (ASDs) are developmental disorders which are thought primarily to affect social functioning. However, there is now a growing body of evidence that unusual sensory processing is at least a concomitant and possibly the cause of many of the behavioural signs and symptoms of ASD. A comprehensive and critical review of the phenomenological, empirical, neuroscientific and theoretical literature pertaining to visual processing in ASD is presented, along with a brief justification of a new theory which may help to explain some of the data, and link it with other current hypotheses about the genetic and neural aetiologies of this enigmatic condition.

Cognitive control in children with ADHD-C: how efficient are they?

The literature on children with attention deficit/hyperactivity disorder, combined type (ADHD-C), is currently inconclusive as to the nature of deficits in two forms of cognitive control - interference control and response selection (Nigg, 2006). This paper examined the performance of children with ADHD-C on interference control and response selection conflict tasks that required both speed and accuracy. The data was analyzed utilizing a new efficiency method to more effectively analyze overall responses. Both interference control and response selection conditions were combined within tasks allowing for a closer comparison of how children with ADHD-C perform on these specific types of cognitive control. Computerized tasks were administered to 62 boys, ages 7 to 12 (31 controls, 31 ADHD-C). Results revealed deficits in efficient performance for children with ADHD-C on interference control tasks and response selection tasks hypothesized to involve high cognitive control demand. These results highlight the utility of analyzing efficiency data to identify deficits in performance for children with ADHD-C and to foster an increased understanding of cognitive control functioning in this clinical population.

Differential effects of D-amphetamine on red and blue light-induced photic activation: A novel BOLD fMRI assay of human dopamine function

The neurotransmitter dopamine (DA) is implicated in the pathophysiology of central nervous system (CNS) illnesses including Parkinson's disease, attention deficit disorder, schizophrenia, and substance abuse. A better understanding of CNS DA function would be of importance in improving our understanding of these conditions. Several lines of evidence suggest that exploring visual system function may be a useful paradigm for examining DA function. Clinical and basic science findings suggest that the visual response to blue light might prove a useful assay of CNS DA tone. To test this hypothesis, we used the functional magnetic resonance imaging (fMRI) BOLD method to measure visual cortical activation in human subjects (N = 6) in response to 8 Hz flashing red and blue light stimuli during placebo conditions and during the oral administration of 2.5 mg of D-amphetamine, a drug known to increase synaptic concentrations of DA and other monoamine neurotransmitters. There was no effect of D-amphetamine administration on the percent BOLD signal change to red or blue light. However, there was a specific augmentation of the spatial extent of activation (as measured by the number of activated pixels; P = 0.018) to blue, but not red light following D-amphetamine administration. This finding is consistent with our hypothesis that blue light function may have utility as an assay of CNS DA tone. However, several limitations to the study, including the small sample size, low dosage of D-amphetamine, and the fact that D-amphetamine increases synaptic concentrations of DA and other monoamine neurotransmitters do not permit a conclusion regarding a specific role for DA in the observed increase in spatial activation to blue light in the amphetamine condition.

Color perception deficits in co-existing attention-deficit/hyperactivity disorder and chronic tic disorders

Preliminary findings suggest that color perception, particularly of blue-yellow stimuli, is impaired in attention-deficit/hyperactivity disorder (ADHD) as well as in chronic tic disorders (CTD). However, these findings have been not replicated and it is unclear what these deficits mean for the comorbidity of ADHD + CTD. Four groups (ADHD, CTD, ADHD + CTD, controls) of children with similar age, IQ and gender distribution were investigated with the Farnsworth-Munsell 100 Hue Test (FMT) and the Stroop-Color-Word Task using a factorial design. Color perception deficits, as indexed by the FMT, were found for both main factors (ADHD and CTD), but there were no interaction effects. A preponderance of deficits on the blue-yellow compared to the red-green axis was detected for ADHD. In the Stroop task only the 'pure' ADHD group showed impairments in interference control and other parameters of Stroop performance. No significant correlations between any FMT parameter and color naming in the Stroop task were found. Basic color perception deficits in both ADHD and CTD could be found. Beyond that, it could be shown that these deficits are additive in the case of comorbidity (ADHD + CTD). Performance deficits on the Stroop task were present only in the 'pure' ADHD group. Hence, the latter may be compensated in the comorbid group by good prefrontal capabilities of CTD. The influence of color perception deficits on Stroop task performance might be negligible.

Interference control in attention-deficit/hyperactivity disorder: differential Stroop effects for colour-naming versus counting

Deficits in interference control are ascribed to patients suffering from ADHD by a number of cognitive theories. However, previous research using the Stroop Colour Word Interference Task has demonstrated mixed results that may be explained by methodological issues (e.g., possible impact of colour perception abilities on interference liability, different approaches to calculate interference scores, conflation of speed and accuracy factors). Hence, this study included two computerized versions of the Stroop (Colour-Stroop, Counting Stroop) which allowed to calculate separate measures of speed and accuracy, provided a more rigorous approach to calculate interference, and permitted to investigate the effects of stimulus properties on interference. Participants were 14 children with a DSM-IV diagnosis of ADHD combined type and 15 matched controls. Children completed a traditional Stroop as well as both a computerized Colour- and Counting-Stroop. Results indicated that the ADHD group showed higher interference scores than controls in the Colour-Stroop, but not in the Counting-Stroop. Thus, interference control may be not generally impaired in ADHD, and examinations with the Colour Stroop should be interpreted with care.

Inefficient cognitive control in adult ADHD: evidence from trial-by-trial Stroop test and cued task switching performance

Background

Contemporary neuropsychological models of ADHD implicate impaired cognitive control as contributing to disorder characteristic behavioral deficiencies and excesses; albeit to varying degrees. While the traditional view of ADHD postulates a core deficiency in cognitive control processes, alternative dual-process models emphasize the dynamic interplay of bottom-up driven factors such as activation, arousal, alerting, motivation, reward and temporal processing with top-down cognitive control. However, neuropsychological models of ADHD are child-based and have yet to undergo extensive empirical scrutiny with respect to their application to individuals with persistent symptoms in adulthood. Furthermore, few studies of adult ADHD samples have investigated two central cognitive control processes: interference control and task-set coordination. The current study employed experimental chronometric Stroop and task switching paradigms to investigate the efficiency of processes involved in interference control and task-set coordination in ADHD adults.

Methods

22 adults diagnosed with persistent ADHD (17 males) and 22 matched healthy control subjects performed a manual trial-by-trial Stroop color-word test and a blocked explicitly cued task switching paradigm. Performance differences between neutral and incongruent trials of the Stroop task measured interference control. Task switching paradigm manipulations allowed for measurement of transient task-set updating, sustained task-set maintenance, preparatory mechanisms and interference control. Control analyses tested for the specificity of group × condition interactions.

Results

Abnormal processing of task-irrelevant stimulus features was evident in ADHD group performance on both tasks. ADHD group interference effects on the task switching paradigm were found to be dependent on the time allotted to prepare for an upcoming task. Group differences in sustained task-set maintenance and transient task-set updating were also found to be dependent on experimental manipulation of task preparation processes. With the exception of Stroop task error rates, all analyses revealed generally slower and less accurate ADHD group response patterns.

Conclusion

The current data obtained with experimental paradigms deliver novel evidence of inefficient interference control and task-set coordination in adults with persistent ADHD. However, all group differences observed in these central cognitive control processes were found to be partially dependent on atypical ADHD group task preparation mechanisms and/or response inconsistency. These deficiences may have contributed not only to inefficient cognitive control, but also generally slower and less accurate ADHD group performance. Given the inability to dissociate these impairments with the current data, it remains inconclusive as to whether ineffecient cognitive control in the clinical sample was due to top-down failure or bottom-up engagement thereof. To clarify this issue, future neuropsychological investigations are encouraged to employ tasks with significantly more trials and direct manipulations of bottom-up mechanisms with larger samples.