A bstract A total of 33 patients with early and continuously-treated phenylketonuria (PKU) between 7 and 16 years of age and 33 matched controls participated in a study ex amining perceptual, central, and re sponse-related mechanisms of infor mation processing. The specific mechanisms studied were: perceptual filtering, memory search, response selection, response execution, and motor presetting. In addition, groups were compared on mean intelligence level and task oriented behaviour. The performance of the PKU pa tients practically matched that of the controls on all three tasks, suggest ing that PKU patients who are con tinuously maintained on a well-con trolled phenylalanine-restricted diet are not impaired in the elementary mechanisms of information process ing. Furthermore, groups did not dif fer in mean IQ or task-oriented be haviour. ConclusionThese results under line the importance of continued, well-controlled dietary treatment. Further studies are recommended to obtain a more complete evaluation of the potential of PKU patients un der these stricter dietary treatment conditions.

The current study was designed to provide a rigorous investigation of the locus of task-inappropriate (impulsive) responding in ADHD children with and without tics. For this purpose we used a variant of Sternberg's (1969) response bias task. The task measures a set of mental operations, namely, preparing a planned response, carrying out or stopping a planned response, and preparing to execute an alternative response. In the first study, we determined the effect of age in a normal sample. As expected, task performance improved as a function of age. Younger children had problems changing a response set. In the second experiment, we compared ADHD children with and without tics with normal children. Unexpectedly, the noticeable task inefficiency of the patient groups was not related to (a) a hasty scan of the display, (b) an inability to change response set, or (c) a speed-accuracy trade-off. Implications for and a discussion about the response inhibition hypothesis in ADHD are discussed.

Thirty patients with early and continuously treated phenylketonuria (PKU) between 8 and 20 years of age were compared with 30 controls, matched individually for age, sex, and educational level of both parents, on behaviour rating scales for parents and teachers as well as a school achievement scale. PKU patients, as a group, demonstrated more problems in task-oriented behaviour and average academic performance than did matched controls. Interestingly, whereas male PKU patients were rated significantly lower on introversion by their teachers, female patients were rated significantly higher on introversion and lower on extraversion than matched controls. This sex difference was also reflected in the relationship between measures of dietary control and the behaviour clusters, suggesting that male and female patients respond differently to elevated Phe levels or the stress associated with PKU. The teacher rating on average academic performance of the PKU patients was associated with recent level of dietary control, which suggests that it might be improved by more strict adherence to the diet. In addition, academic performance correlated negatively with the behaviour cluster negative task orientation. Further studies are recommended to obtain a more complete evaluation of this relationship and to replicate the current findings on larger samples. Over the years a number of studies have examined behaviour and school achievement in patients with early treated phenylketonuria (PKU; McKusick 261600). In general, these studies have found that despite early treatment with a phenylalanine (Phe)-restricted diet, PKU patients demonstrate more behavioural and school problems than do healthy controls. The behaviour problems include both internalizing symptoms (e.g. solitary, unresponsive, anxious, depressed mood: Pietz et al 1997; Smith et al 1988; Weglage et al 1992) and externalizing symptoms (e.g. hyperactive, talkative, impulsive, restless: Hendrikx et al 1994; Kalverboer et al 1994; Realmuto et al 1986; Smith et al 1988), but not antisocial or socially negative symptoms (e.g. lying, teasing, disobedience: Kalverboer et al 1994; Pietz et al 1997; Smith et al 1988). With respect to school achievement, studies have shown that patients with early treated PKU more often repeat classes or need special tutoring (Berry et al 1979; Brunner et al 1983; Koch et al 1987; Rey et al 1996; Verkerk 1995), have to work harder than healthy controls to achieve the same results (Weglage et al 1993), or have specific deficits in arithmetic achievement scores (Azen et al 1991; Berry et al 1979; Fishler et al 1987; Koch et al 1987; Weglage et al 1993). Nevertheless, many questions regarding the behavioural and school problems of patients with early treated PKU remain unanswered. For instance, the relationship between behavioural and school problems on the one hand and levels of dietary control on the other is still relatively unclear. The few studies that examined this relationship, have focused primarily on children in primary school (Azen et al ...

The goal of this study was to evaluate the effect of methylphenidate (MPH) and clonidine in comparison with placebo on response inhibition and state regulation in children with Attention Deficit Hyperactivity Disorder (ADHD). The study utilised a double-blind cross-over design in which children were randomly assigned without replacement to placebo, MPH, and clonidine following baseline assessment. The primary dependent measures were derived from children's performance (reaction time and errors) on a GO-NO GO task under three conditions that altered the inter-stimulus interval (ISI) for presented GO-NO GO stimuli: ISI of 1 sec (fast condition), 4 sec (medium condition), and 8 sec (slow condition). Findings indicated no difference in task performance between groups treated for 7 weeks with placebo, MPH, and clonidine. We concluded that the state regulation problem in ADHD is resistant to MPH and clonidine.

Stemerdink BA, van der Molen MW, Kalverboer AF, van der Meere JJ, Hendrikx MMT, Huisman J, van der Schot LWA, Slijper FME. Information processing deficits in children with early and continuously treated phenylketonuria. Acta PEdiatr 1994;(Suppl 407): 106-7. Stockholm. ISSN Thirty-three patients with early and continuously treated classical phenylketonuria (PKU) and 33 controls matched for age, gender, and educational level of both parents, participated in a chronometric study exploring elementary mechanisms of information processing. Subjects performed speeded performance tasks designed to systematically vary the load on perceptual, central, and output-related mechanisms of information processing. A preliminary analysis of the data indicated that the overall performance of patients with early and continuously treated PKU practically matched that of the controls on all three tasks. Although this finding must be interpreted with caution as it is based on only a preliminary analysis of the data, it suggests that PKU patients who are continuously maintained on a well-controlled phenylalanine-restricted diet are not deficient in the elementary mechanisms of processing. Given the mere recent findings indicating that young children with early-treated classical PKU have specific cognitive deficits in the executive function skills, despite relatively strict dietary control, the authors suggest that future studies should focus on these higher-order cognitive processes.While efficient neonatal screening for phenylketonuria (PKU) and early treatment with a diet low i:i phenylalanine (Phe) clearly benefits cognitive development in PKU, many studies have shown that the outcome is not always normal (1). The intelligence tests scores of earlytreated PKU patients are generally within the normal range but often significantly lower than the means of their family members and the mean expected in the general population (2). Additionally, an increased prevalence of behavior problems, learning disabilities, cognitive deficits and attention problems has been noted in these patients (1).The aim of this study was to examine cognitive deficits in patients with early and continuously treated PKU using a chronometric approach to explore elementary information processing mechanisms. The chronometric approach requires a subject to respond as quickly and accurately as pcssible to an imperative stimulus. The dependent measures are mean response time and number of errors. Previous chronometric studies of PKU patients have consistently shown that they perform more slowly and/or less accurately than control groups oli speeded performance tasks (3-1 1).Considering the recent recommendations on stricter dietary control (12), it is important to assess what deficits continue to exist in PKU patients who are treated early and continuously. Patients and methodsThe subjects were 33 PKU patients (mean age 11 years and 8 months; range 7.3-16.8 years) and 33 control children (mean age 11 years and 8 months; range 7.2-16.8 years) matched for age, gender and e...