Biomedical subjects

E Luk

Publications and source records attributed to E Luk.

3 recordsLinked to original sources

PubMed2001

Contextual abnormalities of saccadic inhibition in children with attention deficit hyperactivity disorder.

Abnormalities of executive function are observed consistently in children with attention-deficit hyperactivity disorder (ADHD), and it is hypothesised that these arise because of disruption to a behavioural inhibition system. Executive and inhibitory functions were compared between unmedicated and medicated children with ADHD (combined type), age-matched healthy children and healthy adults. Executive functions were measured using a test of spatial working memory shown previously to be sensitive to ADHD and to stimulant medication. Inhibitory functions were measured using an ocular motor paradigm that required individuals to use task context to control the release of fixation. Context was set according to the probability that a target would appear at either of the two locations. In one block, targets appeared on 80% of trials. In the other block, targets appeared on 20% of trials. The ability to control the release of fixation was inferred from the fixation offset effect (FOE), or the difference in saccade latency when the current fixation is offset 200 ms prior to the onset of the saccade target (gap condition), compared with when there is no offset (overlap condition). Although the healthy children made more errors on the spatial working memory task than the healthy adults, there was no difference between the two groups in their ability to control fixation using context. Both showed a larger FOE when target probability was low. As expected, the unmedicated ADHD group made more errors on the spatial working memory test than the healthy children, although spatial working memory performance was normal in the medicated ADHD group. However, both the unmedicated and medicated ADHD groups were unable to modulate the FOE according to context, and this was due to their inability to voluntarily inhibit saccades when there was a low target probability. These data suggest that the context-based modulation of fixation release is not controlled by the same systems that control executive function. Furthermore, deficits in executive function and inhibitory control appear independent in children with ADHD.

Attention Deficit Disorder with Hyperactivity↗

PubMed2001

Routine outcome measurement in a child and adolescent mental health service: an evaluation of HoNOSCA. The Health of the Nation Outcome Scales for Children and Adolescents.

OBJECTIVE: This paper evaluates a range of properties for a clinician-based instrument designed for routine use in a child and adolescent mental health service (CAMHS). METHOD: The Health of the Nation Outcome Scales for Children and Adolescents (HoNOSCA) is a new outcome measure with great promise. Case vignettes were used to examine interrater reliability. HoNOSCA was implemented for routine outpatient use by multidisciplinary staff with a return rate of 84%. The 305 ratings obtained at assessment were analysed by age, gender and diagnosis. A sample of 145 paired ratings with a 3-month interval were examined for the measurement of change over time. RESULTS: Interrater reliability of the total score indicates moderate reliability if absolute scores are used and good reliability if the total score is used for relative comparisons. Most scales have good to very good reliability. The scales discriminated between age and gender in the expected way. HoNOSCA correlated with clinicians' views of change and was sensitive to change over a 3-month period. The total score seemed a proxy for severity. CONCLUSION: Routine outcome instruments must be explored in settings where they will be used and with realistic training. HoNOSCA appears to be of value in routine outcome measurement and although questions remain about reliability and validity, the results strongly support further investigation.

Adolescent↗

PubMed1999

Executive function and attention deficit hyperactivity disorder: stimulant medication and better executive function performance in children.

BACKGROUND: Executive function deficits have been reported repeatedly in children with Attention Deficit Hyperactivity Disorder (ADHD). Stimulant medication has been shown to be effective in improving cognitive performance on most executive function tasks, but neuropsychological tests of executive function in this population have yielded inconsistent results. Methodological limitations may explain these inconsistencies. This study aimed to measure executive function in medicated and non-medicated children with ADHD by using a computerized battery, the Cambridge Neuropsychological Test Automated Battery (CANTAB), which is sensitive to executive function deficits in older patients with frontostriatal neurological impairments. METHODS: Executive function was assessed in 30 children with ADHD: 15 were stimulant medication naive and 15 were treated with stimulant medication. These two groups were compared to 15 age, sex and IQ matched controls. RESULTS: The unmedicated children with ADHD displayed specific cognitive impairments on executive function tasks of spatial short-term memory, spatial working memory, set-shifting ability and planning ability. Impairments were also seen on spatial recognition memory and delayed matching to sample, while pattern recognition memory remained intact. The medicated children with ADHD were not impaired on any of the above executive function tasks except for deficits in spatial recognition memory. CONCLUSIONS: ADHD is associated with deficits in executive function. Stimulant medication is associated with better executive function performance. Prospective follow-up studies are required to examine these effects.

Adolescent↗