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Biomedical subjects

R Klorman

Publications and source records attributed to R Klorman.

At least 19 recordsLinked to original sources
PubMed1992

Methylphenidate reduces abnormalities of stimulus classification in adolescents with attention deficit disorder.

Forty-eight adolescents with attention deficit disorder (ADD) received placebo and methylphenidate (M = 35.21 mg/day) for 3 consecutive weeks each. ADD patients who received placebo in the first phase of treatment were compared with unmedicated normal adolescents. ADD and normal adolescents did not differ in slope of reaction time as a function of memory load in a Sternberg (1969) memory task. These results may be interpreted as reflecting normal rates of memory search in ADD. However, in comparison with normal subjects, ADD subjects made disproportionately more errors to targets and lacked faster latencies of the P3b component of event-related potentials for targets than nontargets. These findings suggest abnormalities in stimulus classification. Methylphenidate did not affect ADD patients' rates of memory search, but it did reduce misclassifications of targets at high memory loads. The drug also evoked the normal pattern of slower P3b latencies for nontargets by shortening latencies for targets. Thus the stimulant reduced ADD adolescents' abnormalities in stimulus classification.

Adolescent↗
PubMed1992

Effects of sustained-release and standard preparations of methylphenidate on attention deficit disorder.

Nineteen children with attention deficit disorder (ADD) participated in a double-blind trial consisting of four 2-week phases: sustained-release methylphenidate (MPH); standard MPH; a combination of standard and sustained-release MPH; and placebo. Pharmacological treatments were evaluated by means of parent and teacher ratings and open-ended comments, examiner ratings, and patients' performance and event-related potentials during Continuous Performance and Paired-Associate Learning Tests. Results revealed that the MPH conditions were superior to placebo and comparable to one another. Within the limited time frame of the research, the findings suggest comparable effectiveness for sustained-release and standard preparations of MPH.

Attention Deficit Disorder with Hyperactivity↗
PubMed1991

Methylphenidate speeds evaluation processes of attention deficit disorder adolescents during a continuous performance test.

Forty-six Attention Deficit Disorder (ADD) adolescents took a Continuous Performance Test (CPT) under placebo and methylphenidate (35.33 mg/day). The task required pressing one button for targets (p = .133), and another button for nontargets. Subjects displayed a strong bias to make the more frequent negative response before completely evaluating stimuli. Consistent with this assumption, subjects responded faster (by an average of 87 ms) to nontargets than to targets. Methylphenidate increased accuracy and speeded reaction times (RTs) to targets. The drug also increased the amplitude of the P3b component of the event-related potential for nontargets and shortened the latency of P3b for both targets and nontargets. These results suggest increased capacity allocation to and faster evaluation of task stimuli. Finally, the stimulant lengthened relative motor processing time (RT-P3b latency) for nontargets, a finding implying that response processing was accomplished with the benefit of earlier completion of evaluation processes for these stimuli.

Adolescent↗
PubMed1991

Cognitive event-related potentials in attention deficit disorder.

Cognitive event-related potentials (ERPs) have been used to aid in the interpretation of findings that children with Attention Deficit Disorder (ADD) make more errors and react more slowly than nondisabled controls in tests of sustained attention. Coincident with their abnormally poor performance, children with ADD have smaller late positive components of the ERP (especially a wave known as P3b) than their peers with psychiatric diagnoses. Notably, stimulant administration improves the performance of children with ADD and enlarges the amplitude of the late positive waves of their ERPs. These findings are interpreted as reflecting reduced capacity allocation, which, in turn, is increased by stimulant medications. Research on memory scanning suggests that children with ADD are deficient in energetic aspects of information processes and that their excessive slowness in reaction time tests involves stages following memory search and decision, that is, motor processes. The same factors seem to be involved in the amelioration of performance by stimulants, which speed up motor responses but do not affect the latency of P3b. Research on ERPs during selective attention also points to possible disturbances in this aspect of processing, but further research in this area is needed.

Adolescent↗
PubMed1990

Clinical effects of a controlled trial of methylphenidate on adolescents with attention deficit disorder.

Forty-eight attention deficit disorder patients, 12 to 18 years old and without previous stimulant therapy, received a double-blind trial of methylphenidate and placebo for 3 weeks each. Stimulant treatment produced mild side effects and weight reduction. Methylphenidate significantly reduced teachers' and parents' ratings of hyperactivity, inattention, and oppositionality. In addition, patients rated themselves as clinically improved and reported elevated subjective mood during stimulant therapy. Treatment benefits were comparable for patients with and without concurrent conduct or oppositional disorder as well as those with and without past or present depressive disorders. These results support the continued effectiveness of stimulant therapy for attention deficit disorder in adolescence. However, the magnitude of clinical effectiveness reported was smaller than previously found in younger patients.

Adolescent↗
PubMed1990

Effects of methylphenidate on processing negativities in patients with attention-deficit hyperactivity disorder.

This study compared the impact of methylphenidate on patients with Attention-deficit Hyperactivity Disorder (ADHD) with and without aggressive/noncompliant features in an oddball test consisting of a randomly ordered series of loud (frequent) tones, soft (rare) tones, bright (frequent) lights, and dim (rare) lights. In alternate conditions, subjects were required to respond to either the rare tones or the rare lights. These tasks were administered in a drug-free baseline session and after a counterbalanced treatment of 14 days each of methylphenidate (0.3 mg/Kg b.i.d.) and placebo (lactose b.i.d.). In comparison with placebo, methylphenidate resulted in greater accuracy and speed of reactions to targets of both modalities. The amplitude of N1 to auditory nontargets was larger when the target was a rare tone as opposed to a rare light, and this attention-related effect was increased by methylphenidate. The same differential amplitude enhancement by stimulant treatment was found for an early area measure of difference ERPs. In contrast, for N1 to visual nontargets the effect of selective attention (larger amplitude when the target was a rare light vs. a rare tone) was not significant and was not affected by stimulant medication. All these findings were comparable for the three ADHD subgroups, a result attesting to the generality of stimulant effects on information processing.

Arousal↗
PubMed1987

Comments on studies of event-related potentials in neuropsychiatric disorders of development.

Significant advances have been made in this field and the research exhibits state-of-the-art methodological sophistication. The studies reviewed in this section build on methodological as well as conceptual progress in normative ERP research. It is encouraging that current advances in scoring and interpretation of ERP components are used to advantage in the studies discussed. Although these positive features of the studies reviewed prompt some optimism concerning present progress, considerable problems remain, including: interpretive ambiguities of cognitive ERP findings resulting from possible confounding of motivational factors with cognitive functioning; the adequacy of challenge posed by our tasks for subjects at varying levels of ability; the non-specificity of ERP abnormalities with respect to clinical groups; and methodological complications such as the scoring of 'missing' peaks and the increased variability of ERP results due to the use of wide age ranges.

Child↗
PubMed1983

Effects of two doses of methylphenidate on cross-situational and borderline hyperactive children's evoked potentials.

This study involved 27 children displaying cross-situational hyperactivity and 14 youngsters with borderline hyperactivity. For all patients, evoked potentials were recorded after receiving 0 (placebo), 0.3 and 0.6 mg/kg methylphenidate. Under each pharmacologic condition, subjects were administered: a photic stimulation procedure; two versions of the Continuous Performance Test (CPT), which varied in difficulty level; and a discrimination ('oddball') test. Under photic stimulation, methylphenidate reduced the impact of increasing brightness levels on the rates of amplitude increment and latency decrease in the P208 component of the visual evoked response. These results are similar to those obtained by Buchsbaum and Wender (1973) for hyperactive patients with a positive clinical response to amphetamine. In CPT and the discrimination test, the two active dosages of methylphenidate brought about a comparable reduction of placebo levels of errors and reaction time. Analogously, in both versions of CPT, the two active dosages resulted in comparable increases in the amplitude of two components of the late positive complex (LPC; P510 and P740). P510 was identified as a classical P300. In the discrimination test, the effect of the stimulant on the response evoked by the visual non-target was to increase the amplitude of a component (P463) previously identified as P300. These pharmacologic results were nearly identical for borderline and cross-situational patients. In general, the results confirmed previous observations that methylphenidate improves hyperactive children's performance and increases the amplitude of their LPC. Further, these findings support previous observations that hyperactive patients' cognitive processing is optimized by a dosage of 0.3 mg/kg methylphenidate. Finally, the similarity between findings for cross-situational and borderline hyperactive patients is consistent with other evidence that stimulant effects are not limited to classically hyperactive children.

Attention Deficit Disorder with Hyperactivity↗