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Objective: Recent studies have suggested that attention deficit hyperactivity disorder (ADHD) is associated with abnormalities in basal ganglia and prefrontal cortical functioning. However, these studies have primarily relied upon cognitive tasks that reflect impulse control rather than attentional mechanisms. Method: The authors used functional magnetic resonance imaging to investigate the neural correlates of selective and divided attention in a randomized, double-blind, placebo-controlled pharmacological challenge with methylphenidate in 15 adolescents with ADHD (ages 14-17), eight adolescents with reading disorder (ages 12-17), and four adolescents with both reading disorder and ADHD (ages 14-18) who were scanned during both a methylphenidate and a placebo session. Fourteen healthy comparison subjects (ages 12-20) who were not given methylphenidate served as the primary comparison group. Results: During the divided attention task, unmedicated subjects with ADHD or reading disorder recruited the left ventral basal ganglia significantly less than the healthy comparison subjects. Methylphenidate led to an increase in activation in this region but had no effect on task performance. Subjects with ADHD also recruited the middle temporal gyrus significantly less than the comparison subjects, but methylphenidate did not have a direct effect on activation in this region. Conclusions: These results suggest that ADHD is associated with abnormal processing in attentional networks, with specific dysfunction in striatal circuitry. Methylphenidate may act to normalize activity within this network. [ABSTRACT FROM AUTHOR]

Abstract. In this study we analyzed some of the cognitive components that may constitute attention deficit disorder. It consisted of a double-blind, drug-placebo study of 12 children being treated with three doses of methylphenidate and placebo. Results of an attentional test battery, teacher and parent ratings, and blood levels of methylphenidate are reported. In general, performance was best with 0.6 mg/kg of methylphenidate (the highest dose tested) and worst with placebo. It is argued that no single test provides a complete assessment of attentional deficits and that methylphenidate can improve performance by affecting the allocation of cognitive resources to a task. [ABSTRACT FROM AUTHOR]

Abstract. Despite the frequent use of methylphenidate (MPH) in school-aged children with disorders of attention, impulsivity, and activity regulation (attention deficit disorder, ADD), little is known of its clinical pharmacology. The pharmacokinetics of MPH as well as its effects on growth hormone and prolactin were examined after oral administration in 14 boys with ADD ranging in age from 7 to 12 years (mean 10.4 years). Peak concentrations determined in these acute studies were compared with concentrations obtained two hours after MPH administration in another group of children with ADD who were receiving MPH chronically. After a lag phase of approximately 1/2 to 1 hour, MPH reached a peak plasma concentration at 2.5 +/- 0.65 hours after 0.34 mg/kg and 1.9 +/- 0.82 hours after 0.65 mg/kg (mean +/- SD). Terminal half-lives were 2.53 +/- 0.59 and 2.61 +/- 0.29 hours after administration of 0.34 and 0.65 mg/kg, respectively. Observed maximal concentrations ranged from 11.2 +/- 2.7 ng/ml after administration of 0.34, and 20.2 +/- 9.1 ng/ml after administration of 0.65 mg/kg. The mean area under the curve after administration of 0.65 mg/kg was approximately double that calculated at 0.34 mg/kg. Plasma growth hormone increased significantly from an initial (pre-MPH) mean concentration of 4.4 to peak at two hours at 10.5 ng/ml. Prolactin concentration declined significantly from a pre-MPH level of 9.5 to a nadir at 1 1/2 hours of 3.80 ng/ml, supporting the notion that MPH is acting via central dopaminergic mechanisms. MPH concentratious in children receiving doses of 0.34 mg/kg chronically averaged 8.00 +/- 0.91 at two hours, after medication, approximating the mean concentration at the same time observed in the acute study. The concentration of MPH in single "spot" samples obtained at two to three hours after administration of medication were significantly correlated with the percentage of improvement in the abbreviated Conners rating scale, indicating a rela... [ABSTRACT FROM AUTHOR]

Comments on an article on medication overuse in the treatment of attention deficit hyperactivity disorder, previously published in the October 21, 1988, issue of the 'Journal of the American Medical Association.' Review of relevant literature; Fraud in research on the treatment of the disorder.

Estudios recientes señalaron que el trastorno por déficit de atención con hiperactividad (TDAH) se relaciona con anomalías de los ganglios basales y de la función cortical prefrontal. Sin embargo, estos estudios se basaron, fundamentalmente, en pruebas cognitivas que valoran más el control de los impulsos que los mecanismos de la atención. Método: Los autores utilizaron imágenes de resonancia magnética funcional para investigar los correlatos neurales de la atención selectiva y dividida en una prueba de provocación farmacológica aleatorizada, a doble ciego, contralada por placebo con metilfenidato en 15 adolescentes con TDAH (14-17 años), 8 adolescentes con trastorno de la lectura (12-17 años) y 4 adolescentes con trastorno de la lectura y TDAH (14-18 años) que fueron explorados durante una sesión en que recibieron metilfenidato y una sesión en que recibieron placebo. Catorce individuos sanos de control (12-20 años), no tratados con metilfenidato, fueron el principal grupo de control. Resultados: Durante la prueba de atención dividida, los individuos no medicados con TDAH o trastorno de la lectura activaron significativamente menos los ganglios basales ventrales del lado izquierdo que los individuos sanos de control. El metilfenidato favoreció la activación de dicha región, pero no repercutió en la realización de las tareas cognitivas. Los individuos con TDAH también activaron significativamente menos la circunvolución temporal media que los individuos de control, aunque el metilfenidatona tuvo un efecto directo sobre la activación de dicha región. Conclusiones: Estos resultados indican que el TDAH se relaciona con un procesamiento anómalo de los circuitos de atención, destacando la disfunción de los circuitos estriados. El metilfenidato podría desempeñar una función normalizadora de esta red neural. [ABSTRACT FROM PUBLISHER]