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Biomedical subjects

R A Barkley

Publications and source records attributed to R A Barkley.

At least 19 recordsLinked to original sources
PubMed2001

The executive functions and self-regulation: an evolutionary neuropsychological perspective.

Neuropsychology has customarily taken a molecular and myopic view of executive functioning, concentrating largely on those proximal processes of which it may be comprised. Although commendable as a starting point, such an approach can never answer the question, "Why executive functioning?" The present paper encourages neuropsychologists to contemplate the longer-term, functional nature of the executive functions (EFs), using an evolutionary perspective. For purely illustrative purposes, a previously developed model of the EFs is briefly presented and is then examined from an evolutionary perspective. That model views the EFs as forms of behavior-to-the-self that evolved from overt (public) to covert (private) responses as a means of self-regulation. That was necessary given the interpersonal competition that arises within this group-living species. The EFs serve to shift the control of behavior from the immediate context, social others, and the temporal now to self-regulation by internal representations regarding the hypothetical social future. The EFs seem to meet the requirements of a biological adaptation, being an improbable complex design for a purpose that exists universally in humans. Discovering the adaptive problems that the EFs evolved to solve offers an invaluable research agenda for neuropsychology lest that agenda be resolved first by other scientific disciplines. Some adaptive problems that the EFs may have evolved to solve are then considered, among them being social exchange (reciprocal altruism or selfish cooperation), imitation and vicarious learning as types of experiential theft, mimetic skill (private behavioral rehearsal) and gestural communication, and social self-defense against such theft and interpersonal manipulation. Although clearly speculative at the moment, these proposals demonstrate the merit of considering the larger adaptive problems that the EFs evolved to solve. Taking the evolutionary stance toward the EFs would achieve not only greater insight into their nature, but also into their assessment and into those larger adaptive capacities that may be diminished through injury or developmental impairment toward that system.

Adaptation, Psychological↗
PubMed2001

Executive functioning and olfactory identification in young adults with attention deficit-hyperactivity disorder.

Young adults with attention deficit-hyperactivity disorder (ADHD; N = 105) were compared with a control group (N = 64) on 14 measures of executive function and olfactory identification using a 2 (group) X 2 (sex) design. The ADHD group performed significantly worse on 11 measures. No Group X Sex interaction was found on any measures. No differences were found in the ADHD group as a function of ADHD subtype or comorbid oppositional defiant disorder. Comorbid depression influenced the results of only 1 test (Digit Symbol). After IQ was controlled for, some group differences in verbal working memory, attention, and odor identification were no longer significant, whereas those in inhibition, interference control, nonverbal working memory, and other facets of attention remained so. Executive function deficits found in childhood ADHD exist in young adults with ADHD and are largely not influenced by comorbidity but may be partly a function of low intelligence.

Adolescent↗
PubMed2001

Time perception and reproduction in young adults with attention deficit hyperactivity disorder.

Adults with attention deficit hyperactivity disorder (ADHD; n = 104) were compared with a control group (n = 64) on time estimation and reproduction tasks. Results were unaffected by ADHD subtype or gender. The ADHD group provided larger time estimations than the control group, particularly at long intervals. This became nonsignificant after controlling for IQ. The ADHD group made shorter reproductions than did the control group (15- and 60-s intervals) and greater reproduction errors (12-, 45-, 60-s durations). These differences remained after controlling for IQ and comorbid oppositional defiant disorder, depression, and anxiety. Only the level of anxiety contributed to errors (at 12-s duration) beyond the level of ADHD. Results extended findings on time perception in ADHD children to adults and ruled out comorbidity as the basis of the errors.

Adult↗
PubMed2000

Early androgen treatment decreases cognitive function and catecholamine innervation in an animal model of ADHD.

The spontaneously hypertensive rat (SHR) has been used as an animal model of attention deficit hyperactivity disorder (ADHD). The present study was designed to determine whether exposure to elevated androgen levels early in development demonstrated impairments in cognitive functioning, neuroendocrine control, and brain development parallel to those seen in ADHD children. The animals (SHR and Wistar (WKY) controls) were implanted with testosterone on postnatal day 10 and tested for behavior in a spatial cognition paradigm on postnatal day 45. Plasma samples were collected for determination of adrenocorticotrophin hormone (ACTH) and corticosterone levels as indicators of the basal tone of the pituitary-adrenal neuroendocrine axis. In addition, the density of tyrosine hydroxylase-immunoreactive fibers (an indicator of catecholamine innervation) in the frontal cortex was compared between animals. The current data show that early testosterone treatment in SHR animals resulted in additional deficits in spatial memory in the water maze, but was ineffective in altering the response of WKY animals. Furthermore, SHR rats had high basal ACTH and low corticosterone levels that may indicate a dysfunctional stress axis similar to other reports in humans with persistent ADHD. Finally, there was a further suppression of tyrosine hydroxylase-immunoreactivity in the frontal cortex of androgen-treated SHR rats. These results support the hypothesis that early androgen treatment may support the neurobiology of animals with genetic predisposition to hyperactivity, impulsivity and inattention in a manner consistent with the enhanced expression of ADHD-like behaviors.

Adrenocorticotropic Hormone↗
PubMed2000

Commentary on the multimodal treatment study of children with ADHD.

The multimodal treatment study of attention deficit hyperactivity disorder (MTA Study) constitutes a landmark in the history of treatment research in child psychopathology, being the largest single study of its kind ever undertaken. Important findings have emerged from this project, as the papers in the present volume will attest. This commentary focuses on several concerns about the assumptions that appear to have guided the design of the MTA study, particularly its psychosocial treatment component, as well as the manner in which treatment results have been presented to date. In particular, no explicit theory of ADHD appears to have guided the construction of the treatment components, relying instead on implicit theories associated with those treatments, such as the notion that the symptoms of ADHD arise through faulty learning and defective contingencies of reinforcement. Future articles from this study will need to address these and other concerns if the results of the study are to be properly interpreted and the scientific and clinical yield is to be maximized.

Attention Deficit Disorder with Hyperactivity↗
PubMed2000

Multimethod psychoeducational intervention for preschool children with disruptive behavior: two-year post-treatment follow-up.

This paper describes the 2-year post-treatment follow-up of preschool children identified as having high levels of disruptive behavior at kindergarten entry. They were assigned to four treatment conditions: A no-treatment group, parent-training only, treatment classroom only, and the combination of parent training with the treatment classroom. Interventions lasted the entire kindergarten academic year. Initial post-treatment results reported previously indicated no effects for the parent-training program but some efficacy for the classroom intervention program. For this report, the disruptive behavior (DB) children were subdivided into those who did (n = 74) and did not (n = 77) receive the treatment classroom. Two-year post-treatment follow-up results indicated no differences between the classroom treated and untreated DB groups. These groups also failed to differ in the percentage of children using available treatments across the follow-up period. The DB children in both groups had significantly more symptoms of ADHD and ODD than a community control group (N = 47) at follow-up. They also received higher ratings of externalizing problems on the parent Child Behavior Checklist, more severe ratings of behavior problems at home, and ratings of more pervasive behavior problems at school, and had poorer academic skills. Results suggested that early intervention classrooms for DB children may not produce enduring effects once treatment is withdrawn, and that better approaches are needed for identifying those DB children at greatest risk for later maladjustment.

Attention Deficit and Disruptive Behavior Disorder↗
PubMed2000

A pilot study of methylphenidate, clonidine, or the combination in ADHD comorbid with aggressive oppositional defiant or conduct disorder.

A pilot comparison of the safety and efficacy of methylphenidate (MPH) combined with clonidine, clonidine monotherapy, or MPH monotherapy in 6- to 16-year-old children diagnosed with attention deficit hyperactivity disorder (ADHD) and comorbid aggressive oppositional defiant disorder or conduct disorder was completed. Study design was a 3-month, randomized, blinded, group comparison with eight subjects per group. No placebo comparison was used. All three treatment groups showed significant improvements in attention deficits, impulsivity, oppositional, and conduct disordered symptoms as assessed by parent and teacher rating scales and laboratory measures. Significant differences among treatment groups were found only on a few measures. Only the clonidine monotherapy group showed significantly decreased fine motor speed. These results suggest the safety and efficacy of clonidine alone or in combination with MPH for the treatment of ADHD and aggressive oppositional and conduct disorders.

Adolescent↗
PubMed2000

Multi-method psycho-educational intervention for preschool children with disruptive behavior: preliminary results at post-treatment.

Annual screenings of preschool children at kindergarten registration identified 158 children having high levels of aggressive, hyperactive, impulsive, and inattentive behavior. These "disruptive" children were randomly assigned to four treatment conditions lasting the kindergarten school year: no treatment, parent training only, full-day treatment classroom only, and the combination of parent training with the classroom treatment. Results showed that parent training produced no significant treatment effects, probably owing largely to poor attendance. The classroom treatment produced improvement in multiple domains: parent ratings of adaptive behavior, teacher ratings of attention, aggression, self-control, and social skills, as well as direct observations of externalizing behavior in the classroom. Neither treatment improved academic achievement skills or parent ratings of home behavior problems, nor were effects evident on any lab measures of attention, impulse control, or mother-child interactions. It is concluded that when parent training is offered at school registration to parents of disruptive children identified through a brief school registration screening, it may not be a useful approach to treating the home and community behavioral problems of such children. The kindergarten classroom intervention was far more effective in reducing the perceived behavioral problems and impaired social skills of these children. Even so, most treatment effects were specific to the school environment and did not affect achievement skills. These findings must be viewed as tentative until follow-up evaluations can be done to determine the long-term outcomes of these interventions.

Achievement↗
PubMed1999

Predictive power of frontal lobe tests in the diagnosis of attention deficit hyperactivity disorder.

A battery of tests presumed to assess various frontal lobe functions in children was evaluated for the accuracy of the tests in classifying children as having attention deficit hyperactivity disorder (ADHD). Two groups of children were tested: (1) 66 children, ages 6-11 years, with ADHD, and (2) a normal community control group of 64 children of the same age. Results indicated good positive predictive power (PPP) for seven of the tests (ranging from 80 to 90%), suggesting that abnormal scores on these tests may be indicative of the presence of ADHD. However, the rates of negative predictive power (NPP) even for these seven tests were modest (ranging from 50 to 66%). Sensitivity was also poor (ranging from 5 to 43%) as were the levels of false negatives (averaging 40%) creating fair-to-poor overall classification rates for all tests (49 to 70%). It is concluded that while these neuropsychological tests may have some value in clinical evaluations of children's psychological abilities, they may not be useful as the sole criteria for the diagnostic classification of children as ADHD.

Attention Deficit Disorder with Hyperactivity↗
PubMed1998

Attention-deficit hyperactivity disorder and the stress response.

BACKGROUND: Attention-deficit hyperactivity disorder (ADHD) is a developmental disorder whose three main symptoms are impulsiveness, inattention, and hyperactivity. Researchers have proposed that the central deficit in ADHD is one of poor response inhibition. The present studies were designed to look at the functioning of the hypothalamic-pituitary-adrenal (HPA) axis in response to mental stress in aggressive ADHD subjects participating in a longitudinal study of various psychosocial treatments. METHODS: Pretest and posttest morning salivary samples for cortisol determination were collected from subjects given a battery of tests. RESULTS: The study shows that ADHD subjects who maintained their diagnosis over the first year of the study had a blunted response to the stressor in comparison to those ADHD subjects who no longer retained the disorder 1 year later. CONCLUSIONS: The data suggest that an impaired response to stress may be a marker for the more developmentally persistent form of the disorder.

Aggression↗
PubMed1998

Psychiatric and psychological morbidity as a function of adaptive disability in preschool children with aggressive and hyperactive-impulsive-inattentive behavior.

Children with high levels of aggressive-hyperactive-impulsive-inattentive behavior (AHII; n = 154) were subdivided into those with (n = 38) and without (n = 116) adaptive disability (+AD/-AD) defined as a discrepancy between expected versus actual adaptive functioning. They were compared to each other and a control group of 47 normal children. Both AHII groups were more likely to have attention deficit hyperactivity disorder (ADHD), oppositional defiant disorder, and conduct disorder than control children; more symptoms of general psychopathology; greater social skills deficits; more parental problems; and lower levels of academic achievement skills. Compared to AHII - AD children, AHII + AD children had (1) more conduct disorder; (2) greater inattention and aggression symptoms; (3) more social problems, less academic competence, and poorer self-control at school; (4) more severe and pervasive behavior problems across multiple home and school settings; and (5) parents with poorer child management practices. Thus, adaptive disability has utility as a marker for more severe and pervasive impairments in AHII children.

Achievement↗
PubMed1997

Toward a broader definition of the age-of-onset criterion for attention-deficit hyperactivity disorder.

OBJECTIVE: To critique the age-of-onset criterion (AOC) for the diagnosis of attention-deficit hyperactivity disorder (ADHD). METHOD: The specific AOC of 7 years for symptoms producing impairment as part of the diagnostic criteria is examined from historical, empirical, conceptual, and pragmatic perspectives. RESULTS: No support could be found for the continued use of this criterion for either clinical or research diagnostic purposes. While both empirical and conceptual grounds exist for viewing ADHD as a disorder that typically has its onset of symptoms during childhood, no support exists for the selection of age 7 years for onset of a valid disorder, either for symptom onset or for onset of impairment. CONCLUSIONS: Several reasons favor dispensing with a precise AOC, either for symptom onset or onset of impairment, not the least of which is that it is scientifically indefensible, poses unwarranted practical problems for the study of older adolescents and adults, and may be arbitrarily discriminatory. Until such time as an empirical justification can be marshaled for a precise AOC for ADHD, the current AOC should be either abandoned or generously broadened to include onset of symptoms during the entire childhood years, in keeping with its conceptualization as a childhood-onset disorder.

Adolescent↗
PubMed1997

Sense of time in children with ADHD: effects of duration, distraction, and stimulant medication.

A recent theory of ADHD predicts a deficiency in sense of time in the disorder. Two studies were conducted to test this prediction, and to evaluate the effects of interval duration, distraction, and stimulant medication on the reproductions of temporal durations in children with ADHD. Study I: 12 ADHD children and 26 controls (ages 6-14 years) were tested using a time reproduction task in which subjects had to reproduce intervals of 12, 24, 36, 48, and 60 s. Four trials at each duration were presented with a distraction occurring on half of these trials. Control subjects were significantly more accurate than ADHD children at most durations and were unaffected by the distraction. ADHD children, in contrast, were significantly less accurate when distracted. Both groups became less accurate with increasing durations to be reproduced. Study II: Tested three doses of methylphenidate (MPH) and placebo on the time reproductions of the 12 ADHD children. ADHD children became less accurate with increasing durations and distraction was found to reduce accuracy at 36 s or less. No effects of MPH were evident. The results of these preliminary studies seem to support the prediction that sense of time is impaired in children with ADHD. The capacity to accurately reproduce time intervals in ADHD children does not seem to improve with administration of stimulant medication.

Adolescent↗
PubMed1997

Attention-deficit/hyperactivity disorder, self-regulation, and time: toward a more comprehensive theory.

This article describes the current clinical view of attention-deficit/hyperactivity disorder (ADHD) and suggests a model of prefrontal lobe executive functions that explains better than current theories the cognitive and behavioral deficits associated with ADHD. The model shows how behavioral inhibition is related to and necessary for the proficient performance of four executive functions that subserve self-regulation: nonverbal working memory; the internalization of speech; the self-regulation of affect, motivation, and arousal; and reconstitution. These functions permit the construction, execution, and control of behavior by internally represented information, which removes behavior from control by the immediate context and brings it under the control of time. ADHD disrupts this process and returns control of behavior to the temporal now. A blindness to past, future, and time more generally, as well as an inability to direct behavior toward the future and to sustain it are among many of the deficits predicted by this model for persons with ADHD.

Attention↗