Working memory - not processing speed - mediates fluid intelligence deficits associated with attention deficit/hyperactivity disorder symptoms

Theta and alpha oscillations may underlie improved attention and working memory in musically trained children

INTRODUCTION

Attention and working memory are key cognitive functions that allow us to select and maintain information in our mind for a short time, being essential for our daily life and, in particular, for learning and academic performance. It has been shown that musical training can improve working memory performance, but it is still unclear if and how the neural mechanisms of working memory and particularly attention are implicated in this process. In this work, we aimed to identify the oscillatory signature of bimodal attention and working memory that contributes to improved working memory in musically trained children.

MATERIALS AND METHODS

We recruited children with and without musical training and asked them to complete a bimodal (auditory/visual) attention and working memory task, whereas their brain activity was measured using electroencephalography. Behavioral, time-frequency, and source reconstruction analyses were made.

RESULTS

Results showed that, overall, musically trained children performed better on the task than children without musical training. When comparing musically trained children with children without musical training, we found modulations in the alpha band pre-stimuli onset and the beginning of stimuli onset in the frontal and parietal regions. These correlated with correct responses to the attended modality. Moreover, during the end phase of stimuli presentation, we found modulations correlating with correct responses independent of attention condition in the theta and alpha bands, in the left frontal and right parietal regions.

CONCLUSIONS

These results suggest that musically trained children have improved neuronal mechanisms for both attention allocation and memory encoding. Our results can be important for developing interventions for people with attention and working memory difficulties.

Fronto-parietal white matter microstructure associated with working memory performance in children with ADHD

INTRODUCTION

Attention Deficit/Hyperactivity Disorder (ADHD) is a neurodevelopmental disorder with many functional impairments thought to be underpinned by difficulties in executive function domains such as working memory. The superior longitudinal fasciculus (SLF) plays an integral role in the development of working memory in neurotypical children. Neuroimaging research suggests reduced white matter organization of the SLF may contribute to working memory difficulties commonly seen in ADHD. This study aimed to examine the relationship between white matter organization of the SLF and working memory in children with ADHD.

METHODS

We examined the association of tract volume and apparent fibre density (AFD) of the SLF with working memory in children with ADHD (n = 64) and controls (n = 58) aged 9-11years. Children completed a computerized spatial n-back task and underwent diffusion magnetic resonance imaging (dMRI). Constrained spherical deconvolution-based tractography was used to construct the three branches of the SLF bilaterally and examine volume and AFD of the SLF.

RESULTS

Regression analyses revealed children with ADHD exhibited poorer working memory, and lower volume and AFD of the left SLF-II compared to healthy controls. There was also an association between reaction time and variability (RT and RT-V) and the left SLF-II. Further analyses revealed volume of the left SLF-II mediated the relationship between ADHD and working memory performance (RT and RT-V).

DISCUSSION

These findings add to the current body of ADHD literature, revealing the potential role of frontoparietal white matter in working memory difficulties in ADHD.

Intra-Subject Variability, Intelligence, and ADHD Traits in a Community-Based Sample

OBJECTIVE

The present study investigates the predictive validity of intra-subject variability (ISV) for ADHD traits in a community-based sample and the stability of the relationship between ISV and fluid intelligence (gf) across the continuum of ADHD traits.

METHOD

Age-residualized data from 426 participants (8-18 years, 6% ADHD) was used to investigate whether ex-Gaussian and DDM parameters derived from simple choice-reaction-time tasks can predict continuously assessed ADHD traits. Multiple-Group-Analyses and Latent-Moderated-Structural-Equations were used to test whether ADHD traits moderate the relationship between ISV and gf.

RESULTS

σ and μ of the ex-Gaussian model as well as DDM parameters drift rate (v) and boundary separation (a) significantly predicted general ADHD traits, while τ predicted attention difficulties specifically. Across the ADHD continuum, σ and v were significant predictors of gf.

CONCLUSION

The results confirm the link between ISV and ADHD. The relationship between ISV and gf appears stable across the ADHD continuum.

Is Processing Speed (Gs) related to Hyperactivity (As a Narrow Cognitive Area of Gps): A Dimensional Approach to Heterogeneity of Clinical and WISC-IV Cognitive Profiles in ADHD From RDoC/HiTOP Perspective

OBJECTIVE

The aim of this study was to investigate the relationship between symptomatology and the Wechsler Intelligence Scale for Children, Fourth Edition (WISC-IV) cognitive profiles in Attention Deficit and Hyperactivity Disorder (ADHD), taking into account clinical heterogeneity.

METHOD

The WISC-IV was administered to 60 children aged 6 to 13 years with ADHD who had not previously taken psychotropic medication. Conners Teacher-Rating Scale (CTRS-R/L) and Conners Parent-Rating Scale (CPRS-R/L) were completed by parents and teachers.

RESULTS

We found a statistically significant positive correlation between the symptoms of hyperactivity/impulsivity and PSI (Processing Speed Index). A statistically significant negative correlation was found between the CTRS-R/L's DSM-IV Inattentive subscale and PRI (Perceptual Reasoning Index). No relationship was found between the inattention or hyperactivity/impulsivity symptomatology with Working Memory Index (WMI). WMI stood out as the most frequently reported weakness among the four index scores.

CONCLUSION

Considering the relationship between the cognitive domains of RDoC (Research Domain Criteria) and dimensions of HiTOP with the ADHD symptom clusters, the assessment of cognitive and behavioral symptoms may be useful for phenotyping ADHD. According to the CHC (Cattell-Horn-Carroll) theory; the positive correlation level between PSI, which is accepted as Gs, and hyperactivity/impulsivity symptoms in people with ADHD may be due to the fact that hyperactivity is one of the narrow cognitive domains of Gps.

Circadian Effects on Attention and Working Memory in College Students With Attention Deficit and Hyperactivity Symptoms

Objective

Individuals with an evening chronotype prefer to sleep later at night, wake up later in the day and perform best later in the day as compared to individuals with morning chronotype. Thus, college students without ADHD symptoms with evening chronotypes show reduced cognitive performance in the morning relative to nighttime (i.e., desynchrony effect). In combination with symptoms presented in attention deficit hyperactivity disorder (ADHD), we predicted that having evening chronotype renders impairment in attention during the morning, when students require optimal performance, amplifying desynchrony.

Method

Four hundred college students were surveyed for evening chronotype and symptoms of ADHD. Of those surveyed, 43 students with evening chronotype (19 with ADHD symptoms) performed laboratory attention tasks and were queried about fatigue during morning and evening sessions.

Results

Students with ADHD symptoms demonstrated a greater decrement in sustained attentional vigilance when abstaining from stimulants and asked to perform cognitive tests at times misaligned with natural circadian rhythms in arousal compared to their non-ADHD counterparts with the same chronotype. While individuals with ADHD symptoms had slower reaction-times during sustained attention tasks in the morning session compared to those without symptoms, there was no significant group difference in working memory performance, even though both groups made more errors in the morning session compared to the evening session.

Conclusion

These findings suggest that evening chronotype students with ADHD symptoms are at a greater disadvantage when having to perform sustained attention tasks at times that are not aligned to their circadian rhythm compared to their neuro-typical peers. The implications of this finding may be useful for the provision of disability accommodations to college age students with ADHD when they are expected to perform tasks requiring sustained attention at times misaligned with their circadian rhythms.

Verbal working memory and processing speed: Correlations with the severity of attention deficit and emotional dysregulation in adult ADHD

Objectives

The Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition (DSM‐5), emphasizes symptoms severity with regard to the diagnosis of attention deficit hyperactivity disorder (ADHD). Many clinicians use neuropsychological test results as objective measures of cognitive functions as part of the diagnostic work‐up. The aim of this study was to investigate whether the psychometric test results regarding verbal working memory and processing speed are useful as indicators of the severity of attention deficits and emotional dysregulation in adults with ADHD.

Methods

This observational cross‐sectional clinical study included 418 adults diagnosed with ADHD according to the DSM‐5. Attention deficit severity was defined based on the inattentive subscale of the Adult ADHD Self‐Report Scale. Emotional dysregulation was assessed with the Deficient Emotional Self‐Regulation scale. Verbal working memory was measured with the Working Memory Index (WMI), and processing speed was measured with the Processing Speed Index (PSI) from the Wechsler Adult Intelligence Scale, third edition.

Results

The full‐scale intelligence quotients of the participants were in the normal range, with expected reductions in verbal working memory and processing speed. Only processing speed was associated with attention deficits (β = −.056, p = .003). The association between the psychometric test result for verbal working memory and processing speed and that between the severity of attention deficits and emotional dysregulation were weak (R² < .1) and mostly non‐significant.

Conclusion

The psychometric index scores for verbal working memory (WMI) and processing speed (PSI) seem to have limited utility as indicators of the severity of attention deficits and emotional dysregulation in adult ADHD patients.

Working Memory and Intraindividual Variability in Response Time Mediate Fluid Intelligence Deficits Associated With ADHD Symptomology

Objective: To determine if decreased fluid intelligence was associated with ADHD, and was mediated by deficits in working memory and intraindividual variability in motor responding. Method: The present study tested 142 young adults from the general population on a range of working memory, response time, and fluid intelligence tasks, and an ADHD self-report symptoms questionnaire. Results: Total and hyperactive ADHD symptoms correlated significantly and negatively with fluid intelligence, but this association was fully mediated by both working memory and intraindividual variability in response time. However, inattentive symptoms were not associated with fluid intelligence. Conclusion: These results have important implications for clinicians using speeded psychometric tests as part of their assessment battery, working memory interventions for ADHD patients that focus on performance improvement without controlling for response consistency, and also demonstrate potential differences in the neuropsychological profiles of ADHD subtypes.

Associations of executive and functional outcomes with full-score intellectual quotient among ADHD adults

Associations between executive and functional impairment, intelligence, and attention deficit hyperactivity disorder (ADHD) have been scarcely investigated among adult populations and lead to inconsistent results. This study tested the impact of intellectual level on executive and functional impairment in a clinical sample of adults diagnosed with ADHD. Participants were recruited in a specialized center for the diagnosis and treatment of ADHD (n=66, mean age=27.9 ± 10.8). Measures included intellectual quotient (IQ, Wechsler Adult Intelligence Scale) categorized as ≤110 or >110, the continuous performance test (CPT3^TM), grade retention, educational attainment, and having an activity (job or studies). Participants with a higher IQ had significantly better functional outcomes than participants with a standard IQ: higher educational attainment, lower grade retention, and often having an activity. Participants with higher IQ performed significantly better on all CPT variables assessing executive functioning. Intelligence seemed to work as a protective factor for executive and functional outcomes in a clinical population of ADHD adults and might reduce long-lasting detrimental consequences in life.

Early Attentional Modulation by Working Memory Training in Young Adult ADHD Patients during a Risky Decision-Making Task

Background: Working memory (WM) deficits and impaired decision making are among the characteristic symptoms of patients affected by attention deficit/hyperactivity disorder (ADHD). The inattention associated with the disorder is likely to be due to functional deficits of the neural networks inhibiting irrelevant sensory input. In the presence of unnecessary information, a good decisional process is impaired and ADHD patients tend to take risky decisions. This study is aimed to test the hypothesis that the level of difficulty of a WM training (WMT) is affecting the top-down modulation of the attentional processes in a probabilistic gambling task. Methods: Event-related potentials (ERP) triggered by the choice of the amount wagered in the gambling task were recorded, before and after WMT with a the dual n-back task, in young ADHD adults and matched controls. For each group of participants, randomly assigned individuals were requested to perform WMT with a fixed baseline level of difficulty. The remaining participants were trained with a performance-dependent adaptive n-level of difficulty. Results: We compared the ERP recordings before and after 20 days of WMT in each subgroup. The analysis was focused on the time windows with at least three recording sites showing differences before and after training, after Bonferroni correction ( p < 0.05 ). In ADHD, the P1 wave component was selectively affected at frontal sites and its shape was recovered close to controls' only after adaptive training. In controls, the strongest contrast was observed at parietal level with a left hemispheric dominance at latencies near 900 ms, more after baseline than after adaptive training. Conclusion: Partial restoration of early selective attentional processes in ADHD patients might occur after WMT with a high cognitive load. Modified frontal sites' activities might constitute a neural marker of this effect in a gambling task. In controls, conversely, an increase in late parietal negativity might rather be a marker of an increase in transfer effects to fluid intelligence.

A meta-analysis on verbal working memory in children and adolescents with ADHD

Objective: Previous meta-analyses have demonstrated verbal working memory (WM) dysfunction in children and adolescents with attention deficit/hyperactivity disorder (ADHD); however, the findings are inconsistent. The main objective of this meta-analysis was to investigate the performance of children and adolescents with ADHD in the Digit Span Backwards (DSB) subtest from the Wechsler Intelligence Scale for Children or Wechsler Adult Intelligence Scale. We also sought to provide an updated meta-analysis on WM in children and adolescents with ADHD.Method: PubMed, PsyINFO, Scopus, and Web of Science were searched to locate studies published between 1990 and 2016 that report DSB scores both of children and adolescents with ADHD and matched controls. Potential moderator variables were also analyzed.Results: Forty-nine studies comparing children and adolescents with ADHD (n = 4956) against healthy controls (n = 3249) generated a medium-sized effect (Hedges' g) of 0.56 (95% CI [0.49, 0.64]), indicating poorer verbal WM performance in those with ADHD. A subgroup meta-analysis of studies with participants aged 8-16 years only demonstrated low heterogeneity (I² = 17.06, cf. 55.50 for the main analysis). Moreover, the meta-regression showed a negative association (β = -.05, p = .02) between DSB performance differences and increasing age, indicating that for every one year increase in age the effect size decreased by .05.Conclusion: These results, which emanated from the largest meta-analysis concerning verbal WM in ADHD reported to date, reinforce WM as a key domain of cognitive dysfunction in ADHD, and point to age as the main variable influencing DSB performance difficulties.

Changing relations among cognitive abilities across development: implications for measurement and research

OBJECTIVE

The constructs of intelligence and executive function (EF) are commonly used in neuropsychological, cognitive, and developmental research, and in the context of clinical assessment. Yet, we have a limited understanding of the changing age-related associations among these cognitive constructs and the implications for measurement and research. The objectives of this study were to compare hypothetical models using intellectual abilities (non-age corrected scores of intelligence or IQ) and experimental measures of EF and to better understand the role of age in determining the associations between these cognitive abilities at two different periods of development. We also incorporated prediction of ADHD-related difficulties.

METHOD

We examined intellectual abilities and EF in a typically developing child sample (N = 250) and young-adult sample (N = 329). We used confirmatory factor analysis to estimate models for each developmental period: a one-factor model of general cognitive ability and a two-factor model of intelligence and EF. ADHD-related difficulties were regressed on the factors from each model.

RESULTS

Age was more strongly related to all cognitive abilities in the child sample than in the young-adult sample. In the factor analytic models, higher amounts of cognitive test score variance were explained by both models in the child sample than in the young-adult sample. Further, in the child sample, the general cognitive ability factor (combining intellectual abilities and EF) was a significant predictor of ADHD-related difficulties, but the separate intellectual ability and EF factors were not.

CONCLUSIONS

Variables highly associated with age (such as intellectual ability and EF) should not be statistically controlled when assessing cognitive constructs especially in child samples when there is rapid change in cognitive abilities.