Visual Attention, Orthographic Word Recognition, and Executive Functioning in Children With ADHD, Dyslexia, or ADHD + Dyslexia

Early visual word processing in children with ADHD: An ERP study

BACKGROUND

Attention-deficit/hyperactivity disorder (ADHD) and reading disability (RD) co-occur frequently. Although reading comprehension difficulties in children with ADHD have been well documented, early visual word processing remains unclear.

AIMS

This study investigated event-related potential (ERP) responses to visual stimuli in children with ADHD (6-12 years) by focusing on the N170 component, which signifies rapid, automatic, and specialized processing of visual words.

PROCEDURES

Twenty children with ADHD and twenty typically developing (TD) children matched for sex and age performed an EEG task and underwent several word reading and reading-related cognitive skills tests.

RESULTS

The results revealed deficits in early neural specialization for Chinese characters among children with ADHD. The coarse-tuning effect in the right hemisphere was less pronounced in children with ADHD compared to TD children, and a fine-tuning effect was absent among the ADHD group. Moreover, the early neural specialization for Chinese characters in children with ADHD correlated with orthographic processing ability and rapid naming speed.

CONCLUSIONS AND IMPLICATIONS

The N170 findings indicate deviant early processing of visual words in children with ADHD, suggesting their reading difficulties may stem from these impairments. Furthermore, orthographic processing and rapid naming may play a vital role in the early specialization for Chinese characters among children with ADHD.

Contrasting Deficits in the Function of the Phonological Loop Between Children With Attention Deficit Hyperactivity Disorder and Reading Disability

Attention Deficit Hyperactivity Disorder (ADHD) and reading disability (RD) often co-occur. Impairments in the phonological loop of working memory are central to RD, but it is unclear whether this is linked to ADHD, especially in Chinese reading. Two experiments were conducted with Chinese children aged 7 to 12 (Experiment 1, n = 65; Experiment 2, n = 60). Immediate and delayed recognition paradigms were used to assess phonological encoding and rehearsal. Both the RD-only and comorbid (ADHD + RD) groups performed worse than the control and ADHD-only groups in response time and accuracy. Notably, the comorbid group performed similarly to the RD-only group, indicating that phonological loop deficits in comorbid children are likely due to RD, not ADHD. This highlights phonological loop function as the key to distinguishing between ADHD and RD.

The underlying neuropsychological and neural correlates of the impaired Chinese reading skills in children with attention deficit hyperactivity disorder

Impaired basic academic skills (e.g., word recognition) are common in children with Attention Deficit Hyperactivity Disorder (ADHD). The underlying neuropsychological and neural correlates of impaired Chinese reading skills in children with ADHD have not been substantially explored. Three hundred and two children with ADHD (all medication-naïve) and 105 healthy controls underwent the Chinese language skill assessment, and 175 also underwent fMRI scans (84 ADHD and 91 controls). Between-group and mediation analyses were applied to explore the interrelationships of the diagnosis of ADHD, cognitive dysfunction, and impaired reading skills. Five ADHD-related brain functional networks, including the default mode network (DMN) and the dorsal attention network (DAN), were built using predefined regions of interest. Voxel-based group-wise comparisons were performed. The ADHD group performed worse than the control group in word-level reading ability tests, with lower scores in Chinese character recognition (CR) and word chains (WS) (all P < 0.05). With full-scale IQ and sustained attention in the mediation model, the direct effect of ADHD status on the CR score became insignificant (P = 0.066). The underlying neural correlates for the orthographic knowledge (OT) and CR differed between the ADHD and the control group. The ADHD group tended to recruit more DMN regions to maintain their reading performance, while the control group seemed to utilize more DAN regions. Children with ADHD generally presented impaired word-level reading skills, which might be caused by impaired sustained attention and lower IQ. According to the brain functional results, we infer that ADHD children might utilize a different strategy to maintain their orthographic knowledge and character recognition performance.

What Factors Contribute to Reading in ADHD: Examining Reading-Related Skills in Children With ADHD Only/Comorbid Developmental Dyslexia

BACKGROUND

ADHD and developmental dyslexia (DD) frequently co-occur. However, it is unclear why some children with ADHD acquire DD while others do not.

METHODS

A total of 830 children (including typically developing controls, ADHD only, DD only, and ADHD + DD groups) of two ages (younger: first-third grade; older: fourth-sixth grade) were assessed on measures of reading ability and reading-related skills.

RESULTS

The clinical groups had different degrees of impairment in each reading-related skill. Regression results found that the four groups had different skills in predicting reading ability in younger and older grades. Especially, rapid automatized naming (RAN) was the only predictor of reading ability in children with ADHD only.

CONCLUSIONS

The study highlights that RAN plays an important role in the reading development of children with ADHD only, reflecting the possible protective role of RAN in reading development.

Distribution of Visual and Oculomotor Alterations in a Clinical Population of Children with and without Neurodevelopmental Disorders

A prospective, non-randomized comparative study was conducted to compare the distribution of oculomotor and visual alterations in children with neurodevelopmental disorders and healthy children without such disorders. Sixty-nine children (aged 6-13 years) were enrolled and divided into three groups: a control group (CG) of 23 healthy children; a group of 18 healthy children with oculomotor abnormalities (OAG); and a group of 28 children with a neurodevelopmental disorder (NDDG), with 15 cases of dyslexia, 7 cases of developmental coordination disorder (DCD) and 6 cases of attention deficit/hyperactivity disorder (ADHD). Significantly worse near stereopsis was found in NDDG compared with CG (p < 0.001) and OAG (p = 0.001). Likewise, a significantly lower amplitude of accommodation was found in NDDG compared with CG in both the right (p = 0.001) and left eyes (p < 0.001). No statistically significant differences between groups were found in the measurement of near and distance phoria (p ≥ 0.557), near point of convergence (p = 0.700) and fusional vergences (p ≥ 0.059). Significantly impaired oculomotor test scores were found in NDDG compared with CG (p < 0.001), with no significant differences between OAG and NDDG (p ≥ 0.063). The comparison between the three types of neurodevelopmental disorders included revealed the presence of a significantly lower amplitude of accommodation in children with DCD compared with dyslexics. Furthermore, less exophoria at near was present in children with dyslexia compared with children with ADHD (p = 0.018) and DCD (p = 0.054). In conclusion, children with dyslexia, ADHD and DCD show an altered oculomotor pattern and a more reduced amplitude of accommodation, not always compatible with the diagnostic criteria of an accommodative insufficiency. Accommodative and binocular vision problems are not always present in these children and cannot be considered an etiologic factor.

Executive Functions in Neurodevelopmental Disorders: Comorbidity Overlaps Between Attention Deficit and Hyperactivity Disorder and Specific Learning Disorders

The present study examines the comorbidity between specific learning disorders (SLD) and attention deficit and hyperactivity disorder (ADHD) by comparing the neuropsychological profiles of children with and without this comorbidity. Ninety-seven schoolchildren from 8 to 14 years old were tested: a clinical sample of 49 children with ADHD (n = 18), SLD (n = 18) or SLD in comorbidity with ADHD (n = 13), and 48 typically-developing (TD) children matched for age and intelligence. Participants were administered tasks and questionnaires to confirm their initial diagnosis, and a battery of executive function (EF) tasks testing inhibition, shifting, and verbal and visuospatial updating. Using one-way ANOVAs, our results showed that all children in the clinical samples exhibited impairments on EF measures (inhibition and shifting tasks) when compared with TD children. A more specific pattern only emerged for the updating tasks. Only children with SLD had significant impairment in verbal updating, whereas children with ADHD, and those with SLD in comorbidity with ADHD, had the worst performance in visuospatial updating. The clinical and educational implications of these findings are discussed.

Link Between Topographic Memory and the Combined Presentation of ADHD (ADHD-C): A Pilot Study

Background: Topographic memory is the ability to reach various places by recognizing spatial layouts and getting oriented in familiar environments. It involves several different cognitive abilities, in particular executive functions (EF), such as attention, working memory, and planning. Children with attention deficit hyperactivity disorder (ADHD) show impairments in inhibitory control, regulation of attention, planning, and working memory. Aim: The aim of this study was to evaluate the topographic memory in children with ADHD-combined subtype (ADHD-C). Method: Fifteen children (8-10 years) with a diagnosis of ADHD-C (DSM-5) (ADHD-C group) were compared to 15 children with typical development (TD group) of the same age. All children performed Raven's colored progressive matrices (CPM) test to obtain a measure related with cognitive functioning. The walking Corsi test (WalCT), a large-scale version of the Corsi block-tapping test, was used to assess topographic memory in experimental environment. Results: A higher impairment was observed in ADHD-C than TD with significant differences in the WalCT, in particular on the topographic short-term memory (TSTM) task, on the topographic learning (TL) task, and on the repetition number (RN) task during the TL task. Perseverative errors were reported in performing the square-sequence in the WalCT. Zero-order correlations showed a positive correlation between TSTM and auditory attention, and memory of design of NEPSY-II and digit span of WISC-IV. No statistically significant differences were found between the ADHD-C group and TD group in the TL task in the WalCT condition. Conclusion: In ADHD-C, initial topographic learning was compromised whereas the long-term retention of learned topographical material seemed to not be impaired. In particular, these impairments seem to be linked with difficulties in sustained attention, in spatial memory for novel visual materials, in a poor working memory, and in perseverative behaviors.