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P Zeiner

Publications and source records attributed to P Zeiner.

10 recordsLinked to original sources
PubMed2001

Notes on the normalizer of a finite subgroup of GL(n,d,Z) in GL(n,d,Z).

A finite algorithm for calculating a finite set of generators for the normalizer of a finite subgroup G of GL(n,d,Z) in GL(n,d,Z) is presented. It is based on an algorithm for the normalizer of a finite subgroup G in GL(n,Z), which has been developed recently by Opgenorth. The normalizer of G in GL(n,d,Z) plays a role for superspace groups analogous to the role that the normalizer of G in GL(n,Z) plays for n-dimensional space groups. It is important for calculating superspace groups with the Zassenhaus algorithm and is needed for testing equivalence of superspace groups.

Journal Article↗
PubMed1999

Response to methylphenidate in boys with attention-deficit hyperactivity disorder.

The response to methylphenidate was examined in 36 boys, aged 7-11 y, with attention-deficit hyperactivity disorder (ADHD) in a double-blind, placebo-controlled, crossover design. Hyperactivity and conduct problems were significantly reduced during methylphenidate treatment. Stimulant medication was associated with improvements on tests of sustained attention, working memory and motor steadiness. When individual changes were studied, it was found that 83% showed a significant improvement in their hyperactivity at home or at school, and for 60% their levels of hyperactive behaviour were within the normal range. High levels of hyperactivity at school and relatively low age were significant predictors of normalization of hyperactivity in at least one setting. However, these predictors could only classify correctly 71% of the children. In clinical practice a trial with stimulants is indicated in ADHD children who show symptoms that are sufficiently severe to cause impairment at home and at school.

Analysis of Variance↗
PubMed1998

No vigilance deficit found in either young schizophrenic or ADHD subjects.

Vigilance deficits have been found in both schizophrenic and ADHD subjects. The two patient groups have never been directly compared on any vigilance measure, however. In the present study 20 early-onset schizophrenics were compared to 20 ADHD adolescents on a Degraded Stimulus Continuous Performance Test (DS-CPT). A comparison group of 30 normal adolescents was also included. Results showed no significant differences between the three groups on any of the DS-CPT measures. Different hypotheses are put forth to explain the findings, among them that the task may be insensitive to identifying sustained attention deficits in adolescent populations.

Adolescent↗
PubMed1998

Altered reinforcement mechanisms in attention-deficit/hyperactivity disorder.

The present study tested eight boys with attention-deficit/hyperactivity disorder (ADHD) and 12 normal boys (comparison group), aged 7-12 years, to investigate the hypothesis that ADHD is associated with a steeper and shorter delay-of-reinforcement gradient than is normal. A two-component schedule of reinforcement was used to deliver trinkets or coins as reinforcers in a game-like test. One component was marked by a signal. During this period reinforcers (coins or trinkets) were delivered every 30 s. This component is called a 30-s fixed interval (FI) schedule of reinforcement and measures changes in reactivity to reinforcers. The other component was in effect when the signal was turned off. Then no reinforcer was ever delivered. This is called an extinction (EXT) component and measures primarily sustained attention. The ADHD children gradually developed hyperactivity to a large extent consisting of bursts of responses with short interresponse times (IRTs) during both schedule components. The response bursts not only constituted a substantial portion of the ADHD overactivity, but may well be a key component of the behaviour commonly described as impulsiveness, the key behavioural characteristic of ADHD. In addition, the ADHD children showed behaviour during the extinction component that may well be described as a sustained-attention deficit: initially stopping when the signal was turned off and then resuming responding some time thereafter as if the signal had been turned on again. The comparison group ceased responding during extinction and did not show impulsiveness. The findings were in accordance with a steeper and shorter delay gradient in ADHD.

Attention↗
PubMed1997

Parent-reported symptoms of hyperactivity and attention deficits predict teacher-reported symptoms.

The object of the study was to examine whether symptoms of attention problems and hyperactivity reported by parents predicted teacher-reported symptoms in a referred sample of boys with the DSM-III-R diagnosis of Attention-deficit Hyperactivity Disorder (ADHD). Data from 48 boys, 7-12 years, were gathered independently from parents and teachers using the Child Behavior Checklist, Teacher's Report Form and the ADHD Rating Scale. Base rate, positive predictive power and negative predictive power were calculated for each symptom and for clusters of symptoms. The positive predictive power for individual symptoms was reasonably high with a mean score of 80%, while the parent-teacher agreement (measured by phi correlations) was low. Our results indicate that in most children referred because of hyperactivity, inattention and impulsivity, parent reports are sufficient to make a diagnostic evaluation. However, when multiple informants are available, data should be obtained from different sources.

Attention Deficit Disorder with Hyperactivity↗