Working memory and reaction time variability mediate the relationship between polygenic risk and ADHD traits in a general population sample

Protocol and preregistration for the CODEC project: measuring, modelling and mechanistically understanding the nature of cognitive variability in early childhood

BACKGROUND

Children's cognitive performance fluctuates across multiple timescales. However, fluctuations have often been neglected in favour of research into average cognitive performance, limiting the unique insights into cognitive abilities and development that cognitive variability may afford. Preliminary evidence suggests that greater variability is associated with increased symptoms of neurodevelopmental disorders, and differences in behavioural and neural functioning. The relative dearth of empirical work on variability, historically limited due to a lack of suitable data and quantitative methodology, has left crucial questions unanswered, which the CODEC (COgnitive Dynamics in Early Childhood) study aims to address.

METHOD

The CODEC cohort is an accelerated 3-year longitudinal study which encompasses 600 7-to-10-year-old children. Each year includes a 'burst' week (3 times per day, 5 days per week) of cognitive measurements on five cognitive domains (reasoning, working memory, processing speed, vocabulary, exploration), conducted both in classrooms and at home through experience sampling assessments. We also measure academic outcomes and external factors hypothesised to predict cognitive variability, including sleep, mood, motivation and background noise. A subset of 200 children (CODEC-MRI) are invited for two deep phenotyping sessions (in year 1 and year 3 of the study), including structural and functional magnetic resonance imaging, eye-tracking, parental measurements and questionnaire-based demographic and psychosocial measures. We will quantify developmental differences and changes in variability using Dynamic Structural Equation Modelling, allowing us to simultaneously capture variability and the multilevel structure of trials nested in sessions, days, children and classrooms.

DISCUSSION

CODEC's unique design allows us to measure variability across a range of different cognitive domains, ages, and temporal resolutions. The deep-phenotyping arm allows us to test hypotheses concerning variability, including the role of mind wandering, strategy exploration, mood, sleep, and brain structure. Due to CODEC's longitudinal nature, we are able to quantify which measures of variability at baseline predict long-term outcomes. In summary, the CODEC study is a unique longitudinal study combining experience sampling, an accelerated longitudinal 'burst' design, deep phenotyping, and cutting-edge statistical methodologies to better understand the nature, causes, and consequences of cognitive variability in children.

TRIAL REGISTRATION

ClinicalTrials.gov - NCT06330090.

Novel genetic loci of inhibitory control in ADHD and healthy children and genetic correlations with ADHD

Cumulative evidence has showed the deficits of inhibitory control in patients with attention deficit hyperactivity disorder (ADHD), which is considered as an endophenotype of ADHD. Genetic study of inhibitory control could advance gene discovery and further facilitate the understanding of ADHD genetic basis, but the studies were limited in both the general population and ADHD patients. To reveal genetic risk variants of inhibitory control and its potential genetic relationship with ADHD, we conducted genome-wide association studies (GWAS) on inhibitory control using three datasets, which included 783 and 957 ADHD patients and 1350 healthy children. Subsequently, we employed polygenic risk scores (PRS) to explore the association of inhibitory control with ADHD and related psychiatric disorders. Firstly, we identified three significant loci for inhibitory control in the healthy dataset, two loci in the case dataset, and one locus in the meta-analysis of three datasets. Besides, we found more risk genes and variants by applying transcriptome-wide association study (TWAS) and conditional FDR method. Then, we constructed a network by connecting the genes identified in our study, leading to the identification of several vital genes. Lastly, we identified a potential relationship between inhibitory control and ADHD and autism by PRS analysis and found the direct and mediated contribution of the identified genetic loci on ADHD symptoms by mediation analysis. In conclusion, we revealed some genetic risk variants associated with inhibitory control and elucidated the benefit of inhibitory control as an endophenotype, providing valuable insights into the mechanisms underlying ADHD.

Distinct mechanisms of attentional suppression: exploration of trait factors underlying cued- and learned-suppression

Attention allows us to focus on relevant information while ignoring distractions. Effective suppression of distracting information is crucial for efficient visual search. Recent studies have developed two paradigms to investigate attentional suppression: cued-suppression which is based on top-down control, and learned-suppression which is based on selection history. While both types of suppression reportedly engage proactive control, it remains unclear whether they rely on shared mechanisms. This study aimed to determine the relationship between cued- and learned-suppression. In a within-subjects design, 54 participants performed a cued-suppression task where pre-cues indicated upcoming target or distractor colors, and a learned-suppression task where a salient color distractor was present or absent. No significant correlation emerged between performance in the two tasks, suggesting distinct suppression mechanisms. Cued-suppression correlated with visual working memory capacity, indicating reliance on explicit control. In contrast, learned-suppression correlated with everyday distractibility, suggesting implicit control based on regularities. These results provide evidence for heterogeneous proactive control mechanisms underlying cued- and learned-suppression. While both engage inhibition, cued-suppression relies on deliberate top-down control modulated by working memory, whereas learned-suppression involves implicit suppression shaped by selection history and distractibility traits.

[Formula: see text] Beyond the rubicon: a continuum approach to investigating the impact of ADHD like characteristics on everyday executive function in children with Tourette Syndrome

Across a range of neurodevelopmental conditions, a diagnosis of attention deficit hyperactivity disorder (ADHD) has been shown to be associated with executive function impairment. However, the DSM-V emphasis upon viewing psychological characteristics as existing on a continuous distributed quantitative dimension has enabled the opportunity to consider the influence of sub-diagnostic or sub-referral levels of these psychological characteristics upon cognitive function. This study adopted a continuum approach to the consideration of this ADHD influence and examined the extent to which the difference in parental reported executive functions between children with Tourette syndrome (TS) or typically developing children could be mediated by a concurrent group difference in the possession of sub-referral levels of ADHD-like characteristics. A total of 146 children, 58 with reported TS diagnosis, participated. Parental report measures of ecological executive functioning, the Child Executive Functioning Inventory, and the Vanderbilt ADHD Diagnostic Parent Rating Scale were employed. The analyses with a full sample and a sub-referral sample revealed significant group differences in most of the key measures. In addition, these measures were highly correlated even when controlling for age and gender. A series of mediation analyses indicated that in all models, the ADHD-like measures significantly mediated the group difference in executive function. These results suggest that sub-referrals levels of ADHD-like characteristics continue to contribute to executive challenges in TS. Future intervention research targeting these executive functions should consider the presence of ADHD-like characteristics at sub-referral levels of possession.

Bipolar-ADHD comorbidity: screening for differences in neurocognition and virtual reality-based cognitive performance

OBJECTIVES

Identification of comorbid attention-deficit/hyperactivity disorder (ADHD) in patients with bipolar disorder (BD) is complicated by overlapping cognitive symptoms and methodological challenges. This cross-sectional study investigated whether virtual reality (VR)-based cognitive assessment that mimics daily life cognitive challenges can aid in the detection of sustained attention impairment in BD individuals with comorbid ADHD (BD + ADHD).

METHODS

Forty-nine fully or partially remitted outpatients with BD, of whom 14 (24%) had BD + ADHD, were assessed with the Cognition Assessment in Virtual Reality (CAVIR) test, including a sustained attention test that involves distractions, and the Screen for Cognitive Impairment in Psychiatry (SCIP). Patients were also rated for mood symptoms and functioning and completed questionnaires assessing subjective cognition and quality of life. Patients' cognitive impairment on the SCIP was estimated with reference to n = 100 demographically comparable healthy control participants.

RESULTS

BD + ADHD participants exhibited more pronounced performance deficits on the CAVIR sustained attention test (t(48) = 2.15, p = .037, d = .66). Notably, deficits on this test were proportional to self-reported daily life concentration difficulties in BD + ADHD individuals. Exploratory analyses revealed that BD + ADHD participants also displayed greater impairment on the SCIP working memory- and delayed verbal learning subtests and greater subjective cognitive complaints than BD patients without this comorbidity (p-levels < .001), but only the difference in subjective cognition survived correction for multiple comparisons (F(1,47) = 14.13, p = .005, np2 = 0.24).

CONCLUSION

Screening for deficits in sustained attention with an ecologically valid VR test involving distracting stimuli may be useful for identifying BD + ADHD individuals.

Attention-deficit/hyperactivity disorder

Attention-deficit/hyperactivity disorder (ADHD; also known as hyperkinetic disorder) is a common neurodevelopmental condition that affects children and adults worldwide. ADHD has a predominantly genetic aetiology that involves common and rare genetic variants. Some environmental correlates of the disorder have been discovered but causation has been difficult to establish. The heterogeneity of the condition is evident in the diverse presentation of symptoms and levels of impairment, the numerous co-occurring mental and physical conditions, the various domains of neurocognitive impairment, and extensive minor structural and functional brain differences. The diagnosis of ADHD is reliable and valid when evaluated with standard diagnostic criteria. Curative treatments for ADHD do not exist but evidence-based treatments substantially reduce symptoms and/or functional impairment. Medications are effective for core symptoms and are usually well tolerated. Some non-pharmacological treatments are valuable, especially for improving adaptive functioning. Clinical and neurobiological research is ongoing and could lead to the creation of personalized diagnostic and therapeutic approaches for this disorder.

Shared genetic etiology between ADHD, task-related behavioral measures and brain activation during response inhibition in a youth ADHD case-control study

Impaired response inhibition is commonly present in individuals with attention-deficit/hyperactivity disorder (ADHD) and their unaffected relatives, suggesting impaired response inhibition as a candidate endophenotype in ADHD. Therefore, we explored whether behavioral and neural correlates of response inhibition are related to polygenic risk scores for ADHD (PRS-ADHD). We obtained functional magnetic resonance imaging of neural activity and behavioral measures during a stop-signal task in the NeuroIMAGE cohort, where inattention and hyperactivity-impulsivity symptoms were assessed with the Conners Parent Rating Scales. Our sample consisted of 178 ADHD cases, 103 unaffected siblings, and 173 controls (total N = 454; 8-29 years), for whom genome-wide genotyping was available. PRS-ADHD was constructed using the PRSice-2 software. We found PRS-ADHD to be associated with ADHD symptom severity, a slower and more variable response to Go-stimuli, and altered brain activation during response inhibition in several regions of the bilateral fronto-striatal network. Mean reaction time and intra-individual reaction time variability mediated the association of PRS-ADHD with ADHD symptoms (total, inattention, hyperactivity-impulsivity), and activity in the left temporal pole and anterior parahippocampal gyrus during failed inhibition mediated the relationship of PRS-ADHD with hyperactivity-impulsivity. Our findings indicate that PRS-ADHD are related to ADHD severity on a spectrum of clinical, sub-threshold, and normal levels; more importantly, we show a shared genetic etiology of ADHD and behavioral and neural correlates of response inhibition. Given the modest sample size of our study, future studies with higher power are warranted to explore mediation effects, suggesting that genetic liability to ADHD may adversely affect attention regulation on the behavioral level and point to a possible response inhibition-related mechanistic pathway from PRS-ADHD to hyperactivity-impulsivity.

ADHD Adults Show Lower Interindividual Similarity in Ex-Gaussian Reaction Time Vectors for Congruent Stimuli Compared to Control Peers

OBJECTIVE

Interindividual similarity refers to how similarly individuals respond when receiving the same stimulus or intervention. In this study, we aimed to examine interindividual similarity in adults with ADHD.

METHOD

We used the cosine similarity index of ex-Gaussian reaction time (RT) vectors of mu, sigma, and tau parameters during a Stroop task.

RESULTS

Our results demonstrate that the ADHD group exhibits a reduced interindividual similarity index in their ex-Gaussian RT vectors for congruent stimuli compared to the healthy control group. Importantly, we did not find significant differences in the interindividual similarity index to incongruent stimuli between both groups, thus suggesting that this reduced index was selective for congruent stimuli.

CONCLUSION

Our findings highlight that ADHD adults exhibit more significant interindividual differences in cognitive functioning when processing congruent stimuli than healthy controls. These results provide new insights into the selective mechanisms underlying ADHD and may contribute to developing new targeted interventions for this disorder.

Fifty years of executive control research in attention-deficit/hyperactivity disorder:What we have learned and still need to know

For 50 years, attention-deficit/hyperactivity disorder (ADHD) has been considered a disorder of executive control (EC), the higher-order, cognitive skills that support self-regulation, goal attainment and what we generally call "attention." This review surveys our current understanding of the nature of EC as it pertains to ADHD and considers the evidence in support of eight hypotheses that can be derived from the EC theory of ADHD. This paper provides a resource for practitioners to aid in clinical decision-making. To support theory building, I draw a parallel between the EC theory of ADHD and the common gene-common variant model of complex traits such as ADHD. The conclusion offers strategies for advancing collaborative research.

Central executive training for ADHD: Impact on organizational skills at home and school. A randomized controlled trial

OBJECTIVE

The current randomized controlled trial (RCT) was the first to examine the benefits of central executive training (CET, which trains the working components of working memory [WM]) for reducing organizational skills difficulties relative to a carefully matched neurocognitive training intervention (inhibitory control training [ICT]).

METHOD

A carefully phenotyped sample of 73 children with attention-deficit/hyperactivity-impulsivity disorder (ADHD; ages 8-13, M = 10.15, SD = 1.43; 20 girls; 73% White/Non-Hispanic) participated in a preregistered RCT of CET versus ICT (both 10-week treatments). Parent-rated task planning, organized actions, and memory/materials management data were collected at pretreatment, posttreatment, and 2-4 month follow-up; teacher ratings were obtained at pretreatment and 1-2 month follow-up.

RESULTS

CET was superior to ICT for improving organizational skills based on teacher report (Treatment × Time interaction: d = 0.61, p = .01, BF₁₀ = 31.61). The CET group also improved significantly based on parent report, but this improvement was equivalent in both groups (main effect of time: d = 0.48, p < .001, BF₁₀ = 3.13 × 10⁷; Treatment × Time interaction: d = 0.29, p = .25, BF₀₁ = 3.73). Post hocs/preregistered planned contrasts indicated that CET produced significant and clinically meaningful (number needed to treat = 3-8) pre/post gains on all three parent (d = 0.50 -0.62) and all three teacher (d = 0.46 -0.95) subscales, with gains that were maintained at 1-2 month (teacher report) and 2-4 month follow-up (parent report) for five of six outcomes.

CONCLUSIONS

Results provide strong initial evidence that CET produces robust and lasting downstream improvements in school-based organizational skills for children with ADHD based on teacher report. These findings are generally consistent with model-driven predictions that ADHD-related organizational problems are secondary outcomes caused, at least in part, by underdeveloped working memory abilities. (PsycInfo Database Record (c) 2023 APA, all rights reserved).

Genotype Data and Derived Genetic Instruments of Adolescent Brain Cognitive Development Study® for Better Understanding of Human Brain Development

The data release of Adolescent Brain Cognitive Development® (ABCD) Study represents an extensive resource for investigating factors relating to child development and mental wellbeing. The genotype data of ABCD has been used extensively in the context of genetic analysis, including genome-wide association studies and polygenic score predictions. However, there are unique opportunities provided by ABCD genetic data that have not yet been fully tapped. The diverse genomic variability, the enriched relatedness among ABCD subsets, and the longitudinal design of the ABCD challenge researchers to perform novel analyses to gain deeper insight into human brain development. Genetic instruments derived from the ABCD genetic data, such as genetic principal components, can help to better control confounds beyond the context of genetic analyses. To facilitate the use genomic information in the ABCD for inference, we here detail the processing procedures, quality controls, general characteristics, and the corresponding resources in the ABCD genotype data of release 4.0.