Sensitivity to reward delay in children with attention deficit hyperactivity disorder (ADHD).

The present study compared the sensitivity to pre- and post-reward delays of children with and without DSM-IV combined type ADHD. Thirty-six children with DSM-IV combined type ADHD and 36 controls completed a signal-detection task. Correct identification of one stimulus produced an immediate reward and then a 3.5 s delay before the next trial (immediate reward). Correct identification of the other stimulus was associated with a 3.5 s delay before reward was delivered (delayed reward). Group differences emerged in response bias toward the immediately rewarded alternative. Children in the ADHD group showed a greater bias toward immediate reward than the controls. Children in the control group showed different patterns of response bias and discriminability following immediate and delayed rewards. For these children discriminability was lower and response bias was greater on trials following delayed reward. Both groups responded more slowly on trials following delayed reward. These findings support the hypothesis that children with ADHD are unusually sensitive to pre-reward delays.

Self-report of ADHD symptoms in university students: cross-gender and cross-national prevalence.

Little research has examined the structure and prevalence of attention-deficit/hyperactivity disorder (ADHD) symptoms in university students, including whether symptom structure conforms to the bidimensional (i.e., inattention and hyperactivity-impulsivity) conceptualization of the Diagnostic and Statistical Manual of Mental Disorders (DSMV-IV; American Psychiatric Association, 1994) and whether self-reported symptoms vary across gender and country. A sample of 1,209 university students from three countries (Italy, New Zealand, and the United States) completed a 24-item self-report measure (the Young Adult Rating Scale) tapping ADHD symptomatology. Factor analyses within the U.S. and New Zealand samples supported a bidimensional symptom structure, whereas weaker support for this conceptualization was provided by the Italian sample. Participants did not vary significantly by gender in symptom report; however, Italian students reported significantly more inattention and hyperactivity-impulsivity symptoms than students from the United States, and students from New Zealand reported more inattention symptoms than students from the United States. The prevalence of self-reported ADHD symptoms beyond DSM-IV thresholds for diagnosis ranged from 0% (Italian women) to 8.1% (New Zealand men). The implications of these results for the use of DSM-IV criteria in identifying university students with ADHD are discussed.

Intellectual, neuropsychological, and academic functioning in long-term survivors of leukemia.

OBJECTIVE: To assess the effects of treatment for acute lymphoblastic leukemia (ALL) on children's cognitive functioning. METHOD: Participants were long-term survivors of ALL treated with cranial irradiation and central nervous system (CNS) chemotherapy (n = 20), or CNS chemotherapy only (n = 21), healthy children (n = 21), and children with chronic asthma (n = 21). The groups were compared on measures of intellectual, neuropsychological, and academic functioning. RESULTS: CNS chemotherapy, with and without cranial irradiation, was associated with significantly lower levels of intellectual and academic functioning. Children with chronic asthma obtained lower scores than healthy controls, but these differences were not significant. Tests of neuropsychological functioning did not consistently separate the groups. CONCLUSIONS: CNS chemotherapy and, to a lesser extent, chronic illness both contribute to the poorer performance of long-term survivors of ALL on measures of intellectual and academic functioning.

Sensitivity to reward frequency in boys with attention deficit hyperactivity disorder.

Compared the sensitivity of boys with and without attention deficit hyperactivity disorder (ADHD) to differences in reward frequency. Fifteen boys with ADHD as diagnosed in the Diagnostic and Statistical Manual of Mental Disorders (3rd ed., rev.; American Psychiatric Association, 1987) and a matched control group completed a signal-detection task in which correct identification of 1 stimulus was rewarded 3 times as often as correct identification of the other. Boys in the ADHD group completed the task twice, on and off medication. Group differences emerged in response bias toward the more frequently rewarded alternative. Boys in the control group showed a stable pattern of response bias, irrespective of which alternative they were last rewarded on. Boys in the ADHD group showed different patterns of response bias following rewards on the 2 alternatives. These results suggest children with ADHD were more sensitive to individual instances of reward compared with controls, whose response bias is governed more by their reinforcement history. Methylphenidate improved discriminability and reduced sensitivity to individual instances of reward in the boys with ADHD.

DSM-IV and ICD-10: a comparison of the correlates of ADHD and hyperkinetic disorder.

OBJECTIVE: To examine directly the extent to which ICD-10 hyperkinetic disorder and DSM-IV attention-deficit/hyperactivity disorder (ADHD) identify the same children with the same difficulties. METHOD: Participants were children referred for symptoms of overactivity, inattention, and impulsivity, and a normal control group. Diagnostic criteria for ICD-10 hyperkinetic disorder and DSM-IV ADHD were applied retrospectively. Four groups were identified: hyperkinetic disorder and ADHD (n = 21), ADHD only (n = 22), clinic control (n = 15), and normal control (n = 19). The groups were compared on measures reflecting the central characteristics of ADHD, neurodevelopmental functioning, academic and cognitive functioning, and the presence of conduct problems. RESULTS: There is some evidence of increased symptom severity in the combined diagnostic group. Few differences emerged on measures of neurodevelopmental, academic, and cognitive functioning. Rates of conduct disturbance were similar in both ADHD groups. CONCLUSIONS: DSM-IV criteria identify a broader group of children than those identified by ICD-10. However, there is substantial overlap between the groups formed with these different criteria.

Children's self-talk under conditions of mild anxiety.

Two studies are described which used think-aloud (Study 1) and verbal thought-listing (Studies 1 and 2) procedures to assess preadolescent children's self-talk under conditions of mild anxiety. The self-talk reported was coded into six theoretically meaningful categories and the relationship between self-talk type and anxiety (state and trait) examined. Increased levels of anxiety were associated with higher rates of negative self-talk, but not clearly associated with other types of self-talk. These results suggest negative self-talk plays a role in the generation or maintenance of anxiety in normal children. From the data, it is unclear to what extent perceived task difficulty contributes to the relationship between trait anxiety and negative self-talk. Assessment of self-regulation (Study 1) identified higher levels of anxiety in children reporting awareness of strategies for managing their anxiety.

Family members' uncertainty about parental chronic illness: the relationship of hemophilia and HIV infection to child functioning.

Examined the relationships among parental and child uncertainty about fathers' illnesses and child internalizing problems. Participants included 65 families in which the father had hemophilia, approximately one half of the fathers also were HIV infected. Within each family, respondents included the father, the mother and one child. Outcome variables included both self- and parent-reported child internalizing behaviors. Results indicated that family members' illness uncertainty was intercorrelated, that child uncertainty about the father's illness predicted both anxiety and depressive symptoms in the child, and that mother's uncertainty predicted child-reported anxiety beyond the child's uncertainty.

The identification of pervasive hyperactivity: is clinic observation necessary?

Three groups of hyperactive children (clinic observed, reported and situational) and a normal control group were compared on measures of behavioural, developmental and cognitive functioning. The clinic observed and reported groups did not differ significantly on any of the dependent variables. Situationally hyperactive children were less active, and had fewer behavioural and social difficulties than children with pervasive hyperactivity. Normal control subjects were distinguished by their better academic and social performance, and the absence of behaviour problems, language delay and hearing concerns. The data support the distinction between pervasive and situational hyperactivity, but not the separation of pervasive hyperactivity into clinic observable and reported hyperactivity.

Surface roughness of glass-ceramic insert-composite restorations: assessing several polishing techniques.

The authors compared the effectiveness of seven polishing methods on glass-ceramic insert-composite restorations placed in plastic resin squares. The polishing methods used carbide dental finishing burs and diamond polishing paste, diamond abrasive finishing burs and diamond polishing paste, diamond abrasive finishing burs and composite resin finishing disks, diamond abrasive finishing burs and composite resin polishing points, diamond abrasive finishing burs only, diamond abrasive finishing burs followed by resin impregnated disks and an aluminum oxide polishing abrasive paste, and diamond abrasive finishing burs followed by diamond polishing paste. All systems achieved comparable smoothness except the carbide finishing burs, which damaged the insert-composite margin.

Natural infections by Cryptosporidium sp. in farm-raised ducks and geese.

Modified Ziehl-Neelsen staining and an indirect immunofluorescent assay appeared to be equally useful for monitoring natural infections with Cryptosporidium sp. in farm-raised Pekin ducklings and Danish goslings. In 73 of 128 ducklings, and in 44 of 74 goslings, Cryptosporidium sp. were detected. Tissues from the bursa of Fabricius are most frequently positive in both species. The presence or absence of the parasite could not be correlated with clinical signs or lesions and/or poor performance of the birds. Oocysts from ducklings could not be transmitted to suckling mice but were infectious for ducklings. Oocysts from calves were infectious for mice but not for ducklings. These findings support the view that mammals and birds have different Cryptosporidium spp.

Dental students' perception of patient anxiety.

This study examined the ability of dental students to assess patients' anxiety during dental treatment, and the relationship between patients' general, waiting room and clinic levels of anxiety. Sixty-six restorative dental patients and 35 Final-year dental students participated in the study. Prior to a routine dental appointment, patients completed visual analogue scales indicating their general and waiting room levels of anxiety. During treatment, patients and dental students completed similar scales to indicate patients' levels of anxiety up to and at that time. Patients' general and waiting room levels of anxiety were found to correlate significantly with their reports of anxiety during treatment. Female patients reported higher levels of anxiety than male patients. The correlations between patient and student ratings of patients' anxiety were small and non-significant, suggesting the students were not accurate in their estimates of patients' anxiety during treatment. It is suggested, therefore, that dental students be encouraged to ask patients directly how they are feeling about the dental situation. Such discussion could take place prior to, or at the beginning of, the dental appointment.

Schedule dependence of the interaction of naloxone and chlordiazepoxide.

Reports that the opiate antagonist, naloxone, blocks the anticonflict effects of diazepam and chlordiazepoxide suggest endogenous opioid involvement in the anxiolytic actions of the benzodiazepines. However, naloxone's ability to antagonize the anticonflict effects of the benzodiazepines is not universal, but schedule specific. The present experiments investigated the importance of the timing of conflict periods and control of reinforcement on the naloxone-benzodiazepine interaction. We tested the effects of naloxone (3 mg/kg, IP) and chlordiazepoxide (5 mg/kg, IP) on acquisition of a successive discrimination schedule, with nonreward periods similar in length and frequency to those of signalled DRL, and on an FI60-s schedule. Chlordiazepoxide increased rewarded responding and, unexpectedly, decreased nonrewarded responding during acquisition of successive discrimination. This reduction in nonrewarded responding was reversed by naloxone. Under the FI60 schedule, chlordiazepoxide increased nonrewarded responding, an effect that was totally blocked by naloxone at the beginning of the FI. Naloxone's ability to reverse the response-releasing effect of chlordiazepoxide decreased later in the FI. These results suggest endogenous opioid systems are involved in the anxiolytic actions of the benzodiazepines when the animal is adapting to recently introduced conflict. Once adaptation occurs, other neurotransmitter systems mediate the actions of the benzodiazepines.

Naloxone and chlordiazepoxide: effects on acquisition of DRL and signalled DRL.

The ability of the opiate antagonist, naloxone, to block the anti-conflict effects of the benzodiazepines suggests endogenous opioid involvement in the mechanism of action of these drugs. However naloxone's ability to attenuate the effects of the benzodiazepines in animal conflict paradigms appears to be schedule specific. It is effective in acquisition of a differential reinforcement of low rates of response (DRL) schedule but not in acquisition of a non-reward successive discrimination schedule. We tested the effects of naloxone and chlordiazepoxide on acquisition of DRL and on acquisition of a version of the same schedule (signalled DRL) which was like successive discrimination in having an explicit visual signal of non-reward. Chlordiazepoxide (5 mg/kg i.p.) impaired DRL responding by increasing burst responding and premature responding close to the criterion interval. Naloxone (3 mg/kg i.p.) alone decreased burst and premature responding, it also blocked the effects of chlordiazepoxide. The signalled DRL schedule produced essentially similar drug effects. Clearly the critical schedule parameter determining whether naloxone will attenuate the anxiolytic actions of the benzodiazepines is not the presence or absence of an explicit signal of conflict.

Naloxone and chlordiazepoxide: effects on acquisition and performance of signalled punishment.

The opiate antagonist, naloxone, has been reported to attenuate the loss of behavioural inhibition produced by benzodiazepines in tasks involving punishment and nonreward. This has led to suggestions that endogenous opioid systems may be involved in the anxiolytic actions of the benzodiazepines. However, the capacity of naloxone to block the effects of benzodiazepines depends on the behavioural schedule used. We tested the effects of naloxone and chlordiazepoxide on acquisition and performance of a signalled punishment schedule. Chlordiazepoxide (5 mg/kg IP) increased both punished and unpunished responding during acquisition and unpunished responding during performance of the conflict schedule. Naloxone (3 mg/kg IP) was essentially without effect on responding and failed to attenuate the punishment-releasing effects of chlordiazepoxide. The failure of naloxone and chlordiazepoxide to interact during acquisition of this punishment schedule is similar to results we obtained with successive discrimination and is in contrast to our findings with a differential reinforcement of low rates schedule. These results are consistent with the view that benzodiazepines reduce behavioural inhibition through two separate routes; that one of these routes depends on the release of endogenous opiates; and that the predominant route depends on schedule parameters.

Naloxone blocks the effects of chlordiazepoxide on acquisition but not performance of differential reinforcement of low rates of response (DRL).

The opiate antagonist naloxone can completely or partially reverse the effects of the benzodiazepines on appetitive behaviours and conflict tasks involving electric shook. If naloxone changes the anxiolytic action of the benzodiazepines it should theoretically, be effective in tasks employing nonreward as well as those employing shock. We tested naloxone and chlordiazepoxide on acquisition and performance of a nonreward task, DRL. With both continuous administration during acquisition of DRL, and intermittent administration during stable performance, chlordiazepoxide (5 mg/kg IP) increased burst responding and shifted the peak of the inter-response time (IRT) distribution curve to shorter IRTs. Naloxone (3 mg/kg IP) blocked the effects of chlordiazepoxide on acquisition of DRL. Naloxone (3 mg/kg and 10 mg/kg IP) did not change the effects of chlordiazepoxide on well-learned performance of the DRL schedule. These results show that endogenous opiates could mediate some but not all of the actions of the benzodiazepines. They also suggest that state-dependent and "truly anxiolytic" effects of the benzodiazepines (McNaughton 1985) may have different pharmacological substrates.

Naloxone fails to block the effects of chlordiazepoxide on acquisition and performance of successive discrimination.

Naloxone reduces the effects of chlordiazepoxide on punishment and on acquisition of differential reinforcement of low rates of response. The present experiments tested whether naloxone also reduces the effects of chlordiazepoxide on a second type of nonreward schedule--successive discrimination. Rats were tested on a variable interval baseline of responding for food with signalled intrusion periods when food was no longer available. Naloxone (3 mg/kg IP) failed to change the effects of chlordiazepoxide (5 mg/kg IP) on either acquisition or performance of this successive discrimination. DRL and successive discrimination differ both in their timing of events and their use of explicit visual stimuli. If these or similar parametric differences account for the present results they considerably weaken conventional accounts of the control of behaviour by reward omission.

Use of a sex rap group in an adolescent medical clinic.

This paper reports on a five-year experience with an open-ended weekly group in an Adolescent Medical Clinical. An interdisciplinary staff leading this group includes a counselor trained in sex education, a nurse, a pediatrician and a psychiatrist. The object of the group is to offer an opportunity to adolescent boys and girls to focus on diverse problems of concern to them in an atmosphere of support and sharing. The initial focus is on sexual issues and leads to family planning, but more importantly, there is a general focus on the constructive organization of their life and on investigation of the growth of personal relationships. This teen group gives staff a medium for understanding clinical problems which concern adolescents, while the adolescents are supported in gaining understanding of themselves. In this process there is a development of trust in the clinic as a whole, with better utilization of the entire Adolescent Program.

Streak camera measurement of subnanosecond plastic scintillator properties.

A streak camera technique with temporal resolution of 20 ps has been used to measure the fluorescence properties of several subnanosecond plastic scintillators. The method employs a vacuum light pipe coupled to an optical streak camera. The scintillators are excited by a 200-ps x-ray pulse generated by a 1.06-microm Nd:YAG laser focused onto an iron target. The time history of the low-energy x-ray pulse is measured with an x-ray streak camera. Results are given for NElll plastic scintillators doped with benzophenone or acetophenone, for PVT doped with butyl-PBD, and for a ZnO phosphor doped with Ga.