Biomedical subjects

David R Coghill

Publications and source records attributed to David R Coghill.

3 recordsLinked to original sources

PubMed2006

Acute neuropsychological effects of methylphenidate in stimulant drug-naïve boys with ADHD II--broader executive and non-executive domains.

BACKGROUND: Accumulating evidence supports methylphenidate-induced enhancement of neuropsychological functioning in attention deficit hyperactivity disorder (ADHD). The present study was designed to investigate the acute effects of the psychostimulant drug, methylphenidate (MPH), on neuropsychological performance in stimulant naïve boys with ADHD. METHODS: Seventy-three drug-naïve boys (age 7-15) with ADHD (combined type) completed neuropsychological tasks from the CANTAB battery under randomised, placebo controlled, double-blind conditions following an acute challenge with either placebo (n = 24), .3 (n = 25) or .6 (n = 24) mg/kg oral MPH. RESULTS: MPH did not impair performance on any task. MPH (.6 mg/kg) lengthened response latencies on a task of Spatial Recognition, shortened response times on a Reaction Time task and restored performance on a Delayed Matching to Sample visual, non-working memory task. Contrary to predictions, MPH did not enhance performance on tasks with a prominent executive component, including Go/NoGo, Spatial Working Memory, Stockings of Cambridge and Attentional Set shifting tasks. CONCLUSIONS: Acute administration of MPH to drug-naïve boys with ADHD did not impair neuropsychological performance. Acute MPH enhanced performance on some aspects of non-executive functioning. MPH-induced slowing of responding on a relatively complex Spatial Recognition memory task and quickened responding on a reaction time task requiring less cognitive resources suggests that MPH may act by improving self-regulatory ability. MPH may not exert its effects on neuropsychological functioning by enhancing executive processes.

Adolescent↗

PubMed2005

Neuropsychological functioning in stimulant-naive boys with hyperkinetic disorder.

BACKGROUND: Although children with hyperkinetic disorder and/or attention deficit hyperactivity disorder (ADHD) show disordered executive neuropsychological functioning, the nature of these changes remains controversial. Additionally, impairments in non-executive neuropsychological functioning have been relatively unexplored. Here, the authors describe the neuropsychological functioning of a sample of stimulant drug-naive boys with hyperkinetic disorder on a battery of neuropsychological tasks sensitive to impairments of both executive and non-executive functions. METHOD: Seventy-five stimulant drug-naive boys meeting diagnostic criteria for ICD-10 hyperkinetic disorder were compared with 70 healthy developing controls matched for age but not IQ on computerized tests of neuropsychological functioning from the Cambridge Neuropsychological Test Automated Battery (CANTAB) and a Go/No-Go inhibition task. RESULTS: Boys with hyperkinetic disorder exhibited impairments on tasks with a prominent executive component--working memory, planning, strategy formation, attentional set-shifting and on a reaction time task. However, they were also impaired on tasks without prominent executive components--pattern and spatial recognition, spatial span, delayed matching to sample and paired associates learning. Contrary to predictions, no impairment was observed on the Go/No-Go inhibition task. CONCLUSIONS: Medication-naive boys with hyperkinetic disorder displayed a broad range of neuropsychological impairments. Deficits were demonstrated on tasks with and without prominent executive components. Impairments were not confined to tasks dependent upon frontostriatal functioning, cannot wholly be explained by deficits in inhibitory control, nor can they be attributed to intelligence or previous exposure to stimulant medication.

Adolescent↗

PubMed2004

Methylphenidate restores visual memory, but not working memory function in attention deficit-hyperkinetic disorder.

RATIONALE: Dysfunction of executive neuropsychological performance, mediated by the prefrontal cortex, has been the central focus of recent attention deficit/ hyperkinetic disorder (AD-HKD) research. The role of other potential neuropsychological "risk factors", such as recognition memory, remains understudied. Further, the impact of methylphenidate (MPH) on key neuropsychological processes in AD-HKD remains poorly understood. OBJECTIVES: To compare the performance of boys with AD-HKD on a spatial working memory (SWM) task and on two non-working memory tasks [a simultaneous and delayed matching-to-sample task (DMtS) and a pattern-recognition task] with that of healthy boys, and to investigate the impact of acute and chronic MPH on performance of these tasks. METHODS: Baseline performance of 75 stimulant-naive boys with AD-HKD was compared with that of 70 healthy boys. The AD-HKD boys were then re-tested following the administration of acute and chronic challenges with MPH (0.3 mg/kg and 0.6 mg/kg) under randomised double-blind placebo controlled conditions. RESULTS: Compared with healthy boys, the AD-HKD boys demonstrated performance deficits on all neuropsychological tasks. A single dose of MPH restored performance on the DMtS task but had no impact on the SWM or pattern-recognition tasks. Chronic MPH administration did not alter performance on the SWM task but did improve performance on both the pattern-recognition and DMtS tasks. However, the acute restorative effect of MPH on DMtS diminished with repeated administration. CONCLUSIONS: Our results suggest that current conceptualisations of the neuropsychological basis of AD-HKD and the proposed therapeutic mechanisms of MPH require broadening.

Adolescent↗