Neurophysiological differences between ADHD and control children and adolescents during the recognition phase of a working memory task

Electrical brain activations in preadolescents during a probabilistic reward-learning task reflect cognitive processes and behavioral strategy

Both adults and children learn through feedback which environmental events and choices are associated with higher probability of reward, an ability thought to be supported by the development of fronto-striatal reward circuits. Recent developmental studies have applied computational models of reward learning to investigate such learning in children. However, tasks and measures effective for assaying the cascade of reward-learning neural processes in children have been limited. Using a child-version of a probabilistic reward-learning task while recording event-related-potential (ERP) measures of electrical brain activity, this study examined key processes of reward learning in preadolescents (8-12 years old; n=30), namely: (1) reward-feedback sensitivity, as measured by the early-latency, reward-related, frontal ERP positivity, (2) rapid attentional shifting of processing toward favored visual stimuli, as measured by the N2pc component, and (3) longer-latency attention-related responses to reward feedback as a function of behavioral strategies (i.e., Win-Stay-Lose-Shift), as measured by the central-parietal P300. Consistent with our prior work in adults, the behavioral findings indicate preadolescents can learn stimulus-reward outcome associations, but at varying levels of performance. Neurally, poor preadolescent learners (those with slower learning rates) showed greater reward-related positivity amplitudes relative to good learners, suggesting greater reward-feedback sensitivity. We also found attention shifting towards to-be-chosen stimuli, as evidenced by the N2pc, but not to more highly rewarded stimuli as we have observed in adults. Lastly, we found the behavioral learning strategy (i.e., Win-Stay-Lose-Shift) reflected by the feedback-elicited parietal P300. These findings provide novel insights into the key neural processes underlying reinforcement learning in preadolescents.

Object Recognition Memory Deficits in ADHD: A Meta-analysis

Object recognition memory allows us to identify previously seen objects. This type of declarative memory is a primary process for learning. Despite its crucial role in everyday life, object recognition has received far less attention in ADHD research compared to verbal recognition memory. In addition to the existence of a small number of published studies, the results have been inconsistent, possibly due to the diversity of tasks used to assess recognition memory. In the present meta-analysis, we have collected studies from Web of Science, Scopus, PubMed, and Google Scholar databases up to May 2023. We have compiled studies that assessed visual object recognition memory with specific visual recognition tests (sample-match delayed tasks) in children and adolescents diagnosed with ADHD. A total of 28 studies with 1619 participants diagnosed with ADHD were included. The studies were assessed for risk of bias using the Quadas-2 tool and for each study, Cohen's d was calculated to estimate the magnitude of the difference in performance between groups. As a main result, we have found a worse recognition memory performance in ADHD participants when compared to their matched controls (overall Cohen's d ~ 0.492). We also observed greater heterogeneity in the magnitude of this deficit among medicated participants compared to non-medicated individuals, as well as a smaller deficit in studies with a higher proportion of female participants. The magnitude of the object recognition memory impairment in ADHD also seems to depend on the assessment method used.

Relationship Between Inhibitory Control and Arithmetic in Elementary School Children With ADHD: The Mediating Role of Working Memory

OBJECTIVES

To test if inhibitory control was a significant predictor for arithmetic in children with ADHD and if the relationship between inhibitory control and arithmetic was mediated by working memory.

METHODS

Eighty-four children (ADHD, n = 54; Non-ADHD, n = 30) were tested on their interference control, behavioral inhibition, working memory, and arithmetic. Regression analysis was used to test the predictive role of inhibitory control in arithmetic. Moreover, mediation analysis was done to test whether working memory mediated the relationship between inhibitory control and arithmetic memory.

RESULTS

Interference control but not behavioral inhibition was a significant predictor for arithmetic. In addition, interference control had direct and indirect effects via working memory on arithmetic.

CONCLUSIONS

Results demonstrated that inhibitory control contributed to arithmetic in children with ADHD. Furthermore, interference control had direct and indirect effects via working memory on arithmetic, suggesting interventions for arithmetic difficulties should involve training on both inhibition and working memory.

Multisensory Enhancement of Cognitive Control over Working Memory Capture of Attention in Children with ADHD

Attention deficit hyperactivity disorder (ADHD) is a common neurodevelopmental disorder in school-age children. Although it has been well documented that children with ADHD are associated with impairment of executive functions including working memory (WM) and inhibitory control, there is not yet a consensus as to the relationship between ADHD and memory-driven attentional capture (i.e., representations in WM bias attention toward the WM-matched distractors). The present study herein examined whether children with ADHD have sufficient cognitive control to modulate memory-driven attentional capture. 73 school-age children (36 with ADHD and 37 matched typically developing (TD) children) were instructed to perform a visual search task while actively maintaining an item in WM. In such a paradigm, the modality and the validity of the memory sample were manipulated. The results showed that under the visual WM encoding condition, no memory-driven attentional capture was observed in TD children, but significant capture was found in children with ADHD. In addition, under the audiovisual WM encoding condition, memory-matched distractors did not capture the attention of both groups. The results indicate a deficit of cognitive control over memory-driven attentional capture in children with ADHD, which can be improved by multisensory WM encoding. These findings enrich the relationship between ADHD and cognitive control and provide new insight into the influence of cross-modal processing on attentional guidance.

Recognition memory for pictures in children with ADHD: an event-related potential study

OBJECTIVE

Children with ADHD are reported to accompany by various degrees of recognition memory cognitive deficits. We aimed to investigate age-related changes of the amplitude in event-related potential recordings on recognition memory in Chinese children with ADHD and to provide theoretical basis of neuro-electrophysiology for the cognition development of children.

METHOD

ERP and behavioral data of 6- to -10-year-old children with ADHD (n = 94) and typically developing controls (TD, n = 96) were collected while the children performed a classical visual study-test paradigm task.

RESULTS

Children with ADHD have defects in pictures recognition and showed a significantly smaller P2 component than that of TD children. The development of P2 and P3 component were different between the two groups. Moreover, the TD children showed the frontal old/new effect (N2) taken as a correlate of familiarity at 6 years old, and a parietal old/new effect (P3) taken as a correlate of recollection at 9 years old, while children with ADHD showed a parietal old/new effect (P3) only at 6 years old.

CONCLUSION

Our study provided the novel evidence that recognition memory follow different developmental trajectories at the age of 6-10 between TD and ADHD.

A New Paradigm for Training Hyperactive Dopamine Transporter Knockout Rats: Influence of Novel Stimuli on Object Recognition

Attention deficit hyperactivity disorder (ADHD) is believed to be connected with a high level of hyperactivity caused by alterations of the control of dopaminergic transmission in the brain. The strain of hyperdopaminergic dopamine transporter knockout (DAT-KO) rats represents an optimal model for investigating ADHD-related pathological mechanisms. The goal of this work was to study the influence of the overactivated dopamine system in the brain on a motor cognitive task fulfillment. The DAT-KO rats were trained to learn an object recognition task and store it in long-term memory. We found that DAT-KO rats can learn to move an object and retrieve food from the rewarded familiar objects and not to move the non-rewarded novel objects. However, we observed that the time of task performance and the distances traveled were significantly increased in DAT-KO rats in comparison with wild-type controls. Both groups of rats explored the novel objects longer than the familiar cubes. However, unlike controls, DAT-KO rats explored novel objects significantly longer and with fewer errors, since they preferred not to move the non-rewarded novel objects. After a 3 months' interval that followed the training period, they were able to retain the learned skills in memory and to efficiently retrieve them. The data obtained indicate that DAT-KO rats have a deficiency in learning the cognitive task, but their hyperactivity does not prevent the ability to learn a non-spatial cognitive task under the presentation of novel stimuli. The longer exploration of novel objects during training may ensure persistent learning of the task paradigm. These findings may serve as a base for developing new ADHD learning paradigms.