DRD4 genotyping may differentiate symptoms of attention-deficit/hyperactivity disorder and sluggish cognitive tempo

Objective: Studies to reduce the heterogeneity of attention-deficit/hyperactivity disorder (ADHD) have increased interest in the concept of sluggish cognitive tempo (SCT). The aim of this study was to investigate if the prevalence of two variable-number tandem repeats (VNTRs) located within the 3′-untranslated region of the DAT1 gene and in exon 3 of the dopamine D4 receptor (DRD4) gene differ among four groups (31 subjects with SCT but no ADHD, 146 individuals with ADHD but no SCT, 67 subjects with SCT + ADHD, and 92 healthy controls). Methods: We compared the sociodemographic profiles, neurocognitive domains, and prevalence of two VNTRs in SCT and ADHD subjects versus typically developing (TD) controls. Results: The SCT without ADHD group had a higher proportion of females and lower parental educational attainment. Subjects in this group performed worse on neuropsychological tests, except for psychomotor speed and commission errors, compared to controls. However, the ADHD without SCT group performed significantly worse on all neuropsychological domains than controls. We found that 4R homozygosity for the DRD4 gene was most prevalent in the ADHD without SCT group. The SCT without ADHD group had the highest 7R allele frequency, differing significantly from the ADHD without SCT group. Conclusion: The 7R allele of DRD4 gene was found to be significantly more prevalent in SCT cases than in ADHD cases. No substantial neuropsychological differences were found between SCT and ADHD subjects.

Disproportionate Decline of Executive Functions in Early Mild Cognitive Impairment, Late Mild Cognitive Impairment, and Mild Alzheimer's Disease

BACKGROUND AND PURPOSE: Many literatures indicate that executive dysfunction exists in mild cognitive impairment (MCI) as well as Alzheimer’s disease (AD). However, there are few studies that found how early the deficits of the executive function (EF) exist in MCI. The present study investigated the presence of executive dysfunctions in the earliest stage of MCI, and the sub-domains of EF which are disproportionately impaired earlier than others. METHODS: The participants were 41 normal elderly (NE), 86 with amnestic multi-domain MCI, and 41 with mild AD. The MCI group was further sub-divided into two groups: Early MCI (EMCI, n=45) and late MCI (n=41), based on the Clinical Dementia Rating-Sum of Boxes. All participants were given neuropsychological tests to assess the sub-domains of EF, such as verbal fluency, psychomotor speed, inhibitory control, and mental set-shifting. RESULTS: Impairment of semantic fluency was observed in EMCI, with gradual worsening as cases approached mild AD. Phonemic fluency and psychomotor speed were also impaired at the early stage of MCI relative to the NE, but maintained at the same level up to mild AD. EMCI exhibited the same degree of performance with NE for inhibitory control and mental set-shifting; however, they progressively worsened from EMCI to mild AD. CONCLUSIONS: These results suggest that impairments of EF exist even in the earliest stage of the MCI, with a disproportionate decline in the sub-domains of EF.

Korean Wechsler Intelligence Scale for Children-Fourth Edition Profiles in Child and Adolescent with Attention-Deficit Hyperactivity Disorder : Retrospective Study

OBJECTIVES: The aim of this study was to investigate Korean Wechsler Intelligence profiles and specific abilities related to attention problem of children with attention-deficit hyperactivity disorder (ADHD). METHODS: The Korean Wechsler Intelligence Scale for Children-fourth edition (K-WISC-IV) and Advanced Test of Attention (ATA) were administered to 91 children and adolescents (age 8.5+/-2.6 years, 73 boys) with ADHD. Pearson correlation and independent t-tests were used. RESULTS: The means of Working Memory Index (WMI) and Processing Speed Index (PSI) showed a score of low average in K-WISC-IV. WMI scores for the K-WISC-IV showed clinically significant correlations with omission errors, commission errors, and response time variability on auditory ATA. PSI scores also showed significant correlations with response time and variability on visual ATA. In addition, significantly lower digit span backward scores were observed in hyperactive-impulsive/combined subtypes compared to inattentive subtype (t=3.60, p<.001). CONCLUSION: Children with ADHD showed significantly lower scores in WMI and PSI which were clinically correlated with ATA scores, and hyperactive-impulsive/combined subtypes showed poorer working memory functions in WMI. Follow-up studies are proposed.