Working Memory Capacity and ADHD Symptoms in Boys: Examining the Heterogeneity of Working Memory Functioning Using Latent Profile Analysis

Memory deficits and hippocampal cytokine expression in a rat model of ADHD

Attention-deficit/hyperactivity disorder (ADHD) is a complex behavioral disorder characterized by hyperactivity, impulsivity, inattention, and deficits in working memory and time perception. While animal models have advanced our neurobiological understanding of this condition, there are limited and inconsistent data on working and elapsed time memory function. Inflammatory signaling has been identified as a key factor in memory and cognitive impairments, but its role in ADHD remains unclear. Additionally, the disproportionate investigation of male subjects in ADHD research has contributed to a poor understanding of the disorder in females. This study sought to investigate the potential connections between memory, neuroimmunology, and ADHD in both male and female animals. Specifically, we utilized the spontaneously hypertensive rat (SHR), one of the most extensively studied animal models of ADHD. Compared to their control, the Wistar-Kyoto (WKY) rat, male SHR are reported to exhibit several behavioral phenotypes associated with ADHD, including hyperactivity, impulsivity, and poor sustained attention, along with impairments in learning and memory. As the hippocampus is a key brain region for learning and memory, we examined the behavior of male and female SHR and WKY rats in two hippocampal-dependent memory tasks. Our findings revealed that SHR have delay-dependent working memory deficits that were similar to, albeit less severe than, those seen in hippocampal-lesioned rats. We also observed impairments in elapsed time processing in female SHR, particularly in the discrimination of longer time durations. To investigate the impact of inflammatory signaling on memory in these rats, we analyzed the levels of several cytokines in the dorsal and ventral hippocampus of SHR and WKY. Although we found some sex and genotype differences, concentrations were generally similar between groups. Taken together, our results indicate that SHR exhibit deficits in spatial working memory and memory for elapsed time, as well as some differences in hippocampal cytokine concentrations. These findings contribute to a better understanding of the neurobiological basis of ADHD in both sexes and may inform future research aimed at developing effective treatments for the disorder. Nonetheless, the potential mediating role of neuroinflammation in the memory symptomatology of SHR requires further investigation.

Concurrent and Prospective Associations of Reward Response with Affective and Alcohol Problems: ADHD-Related Differential Vulnerability

Attention-deficit/hyperactivity disorder (ADHD) is a heterogeneous disorder. Data on the role of transdiagnostic, intermediate phenotypes in ADHD-relevant characteristics and outcomes are needed to advance conceptual understanding and approaches to precision psychiatry. Specifically, the extent to which the association between neural response to reward and ADHD-associated affective, externalizing, internalizing, and substance use problems differ depending on ADHD status is unknown. Aims were to examine, in 129 adolescents, whether concurrent and prospective associations of fMRI-measured initial response to reward attainment (relative to loss) with affectivity and externalizing, internalizing, and alcohol use problems differs between youth at-risk for (i.e., subclinical) (n = 50) and not at-risk for ADHD. Adolescents were, on average, 15.29 years old (SD = 1.00; 38% female), 50 were at-risk for (M_age = 15.18 years, SD = 1.04; 22% female) and 79 not at-risk for (M_age = 15.37 years, SD = 0.98; 48.1% female) ADHD. Both concurrent and prospective relations differed given ADHD risk: across analyses, in at-risk youth, greater superior frontal gyrus response was associated with lower concurrent depressive problems but in not at-risk youth, these characteristics were not related. Controlling for baseline use, in at-risk youth, greater putamen response was associated with greater 18-month hazardous alcohol use, whereas in not at-risk youth, greater putamen response was associated with lower use. Where in brain and for which outcomes modulate (direction of) observed relations: superior frontal gyrus response is relevant for depressive problems whereas putamen response is relevant for alcohol problems and greater neural responsivity is linked to less depressive but to more alcohol problems in adolescents at-risk for ADHD and less alcohol problems in adolescents not at-risk. Differences in neural response to reward differentially confer vulnerability for adolescent depressive and alcohol problems depending on ADHD risk.

Latent structure of working memory and emotion regulation in pediatric ADHD

Working memory is a key cognitive function that is often implicated in ADHD and may represent an underlying cognitive endophenotype of the disorder. Working memory is related to emotion regulation, which is a common area of impairment in children with ADHD. Given the high rate of comorbid diagnoses with ADHD, children with comorbid internalizing, externalizing, and developmental disorders may present with variable working memory profiles and subsequent emotion regulation deficits. This study aimed to adequately characterize the latent structure of working memory impairments and emotional regulation outcomes in a clinical sample of children ages 6-16 with ADHD. This study also examined the interplay between the identified working memory/emotion regulation patterns, demographic characteristics, and the role of comorbid diagnoses. Results highlighted two distinct, invariant, unrestricted classes of working memory/emotion regulation. Class 1 (Average; 62% of the sample) had significantly lower digit-span scores, and generally persevered emotion regulation functioning per parent/teacher report. Class 2 (Emotionally Dysregulated) had average working memory scores, and elevated emotion regulation problems. The working memory indicators had small correlations with parents (and not teacher) measures of emotion regulation. Finally, latent class membership did not differ by comorbid diagnosis, age, gender, or verbal IQ. Findings elucidate heterogeneity in common domains affected by ADHD and suggest that this heterogeneity may not be due to demographic/comorbidity factors. The role of varying information reports is discussed, and potential assessment and treatment implications are highlighted.

Adolescent ADHD and electrophysiological reward responsiveness: A machine learning approach to evaluate classification accuracy and prognosis

We evaluated event-related potential (ERP) indices of reinforcement sensitivity as ADHD biomarkers by examining, in N=306 adolescents (M_age=15.78, SD=1.08), the extent to which ERP amplitude and latency variables measuring reward anticipation and response (1) differentiate, in age- and sex-matched subsamples, (i) youth with vs. without ADHD, (ii) youth at-risk for vs. not at-risk for ADHD, and, in the with ADHD subsample, (iii) youth with the inattentive vs. the hyperactive/impulsive (H/I) and combined presentations. We further examined the extent to which ERP variables (2) predict, in the ADHD subsample, substance use (i) concurrently and (ii) prospectively at 18-month follow-up. Linear support vector machine analyses indicated ERPs weakly differentiate youth with/without (65%) - and at-risk for/not at-risk for (63%) - ADHD but better differentiate ADHD presentations (78%). Regression analyses showed in adolescents with ADHD, ERPs explain a considerable proportion of variance (50%) in concurrent alcohol use and, controlling for concurrent marijuana and tobacco use, explain a considerable proportion of variance (87 and 87%) in, and predict later marijuana and tobacco use. Findings are consistent with the dual-pathway model of ADHD. Results also highlight limitations of a dichotomous, syndromic classification and indicate differences in neural reinforcement sensitivity are a promising ADHD prognostic biomarker.

[Influence of sleep quality on symptoms in children with attention deficit hyperactivity disorder: the mediating role of working memory]

OBJECTIVES

To study the mediating role of working memory between sleep quality and symptoms in children with attention deficit hyperactivity disorder (ADHD).

METHODS

The cluster random sampling method was used to select 110 ADHD children and 124 normal children as subjects from grade 3-5 students in two primary schools in Kashgar, Xinjiang Uygur Autonomous Region, China. SNAP-IV, Pittsburgh Sleep Quality Index (PSQI), and visual-spatial working memory paradigm were used for investigation and comparison.

RESULTS

Compared with the normal group, the ADHD group had a significantly higher total score of PSQI and scores of subjective sleep quality, sleep latency, sleep efficiency, sleep disturbance, and a higher incidence of sleep quality problems (P<0.001). The working memory score in the ADHD group was significantly lower than that in the normal group (P<0.001). In the ADHD group, the working memory score was negatively correlated with the total score of PSQI (rs=-0.271, P<0.001) and the score of symptoms (rs=-0.439, P<0.001), and the total score of PSQI was positively correlated with the score of symptoms (rs=0.540, P<0.001). Working memory had a partial mediating effect in the influence of sleep quality on symptoms in children with ADHD, accounting for 18.10% of the total effect.

CONCLUSIONS

Sleep quality issues are observed in some children with ADHD, and working memory plays a mediating role between sleep quality and symptoms in ADHD children.

Immediate and Sustained Effects of Neurofeedback and Working Memory Training on Cognitive Functions in Children and Adolescents with ADHD: A Multi-Arm Pragmatic Randomized Controlled Trial

OBJECTIVE

To evaluate the effects of neurocognitive training methods on targeted cognitive functions in children and adolescent with ADHD.

METHOD

A pragmatic four-arm randomized controlled trial compared two types of neurofeedback (Slow Cortical Potential and Live Z-score) and Working-memory training (WMT) with treatment as usual. N = 202 participants with ADHD aged 9 to 17 years were included. A battery of cognitive function tests was completed pretreatment, posttreatment, and after 6-months.

RESULTS

The effects of WMT on spatial and verbal working-memory were superior to neurofeedback and treatment as usual at posttreatment, but only partially sustained at follow-up. No other consistent effects were observed. We found no clear indications that effects were moderated by ADHD presentation, ongoing medication, age, or sex.

CONCLUSION

The sustained effects of neurocognitive training on cognitive functioning in children and adolescents with ADHD may be limited. Future research should focus on more personalized forms of neurocognitive training.

Neural basis of working memory in ADHD: Load versus complexity

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Working memory (WM).

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Load versus Complexity.

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ADHD.

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FMRI.

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Working Memory Striatum and Cerebellum.

Working memory (WM) deficits are key in attention deficit hyperactivity disorder (ADHD). Nevertheless, WM is not universally impaired in ADHD. Additionally, the neural basis for WM deficits in ADHD has not been conclusively established, with regions including the prefrontal cortex, cerebellum, and caudate being implicated. These contradictions may be related to conceptualizations of WM capacity, such as load (amount of information) versus operational-complexity (maintenance-recall or manipulation). For instance, relative to neurotypical (NT) individuals, complex WM operations could be impaired in ADHD, while simpler operations are spared. Alternatively, all operations may be impaired at higher loads. Here, we compared the impact of these two components of WM capacity: load and operational-complexity, between ADHD and NT, behaviorally and neurally. We hypothesized that the impact of WM load would be greater in ADHD, and the neural activation would be altered. Participants (age-range 12–23 years; 50 ADHD (18 females); 82 NT (41 females)) recalled three or four objects (load) in forward or backward order (operational-complexity) during functional magnetic resonance imaging scanning. The effects of diagnosis and task were compared on performance and neural engagement. Behaviorally, we found significant interactions between diagnosis and load, and between diagnosis, load, and complexity. Neurally, we found an interaction between diagnosis and load in the right striatum, and between diagnosis and complexity in the right cerebellum and left occipital gyrus. The ADHD group displayed hypo-activation compared to NT group during higher load and greater complexity. This informs mechanisms of functional problems related to WM in adolescents and young adults with ADHD (e.g., academic performance) and remedial interventions (e.g., WM-training).