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Biomedical subjects

R Klorman

Publications and source records attributed to R Klorman.

At least 37 records · Page 2Linked to original sources
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↗
PubMed1981

Learning-disordered children's evoked potentials during sustained attention.

Evoked potentials and performance of 19 learning-disordered (LD) and 19 normally achieving children were studied in two versions of the Continuous Performance Test (CPT). In both CPT procedures, LD children made more errors of omission and commission than did normal children. Evoked potential differences between groups were especially prominent in the more difficult BX version of the CPT. LD children displayed significantly smaller late positive components (LPC) of the evoked potential to critical stimuli in the task. There were no LPC differences between diagnostic groups for noncritical stimulus categories. The results suggest a deficit in behavioral and cortical indices of sustained attention among LD children.

Adolescent↗
PubMed1981

Effect of methylphenidate on young adult's vigilance and event-related potentials.

Two studies were conducted on the effects of methylphenidate (20 mg) on young adults' event-related potentials. Although this stimulant elevated heart rate in study 1 (n = 14), it failed to affect either performance or amplitude of the late positive component (LPC) obtained from two versions of the continuous performance test (CPT). Because performance on these tasks was nearly error-free, we conducted study 2 (n = 23) to test the hypothesis that methylphenidate enlarges LPC amplitude only in more challenging tests than those used in study 1. In study 2, although heart rate was again elevated by the 20 mg dose of methylphenidate, LPC amplitude and performance were again unaffected in the two tasks employed in study 1 or in an easy tone discrimination procedure. However, in a more difficult version of CPT (10% errors of omission), both accuracy and amplitude of the concurrently obtained LPC were increased by methylphenidate. Similarly, in a choice-reaction time test, the stimulant increased speed as well as CNV amplitude. Our interpretation of the results is based on the view that LPC reflects the number of attentional resources committed to a stimulus during the evaluation stage. Thus, increases in LPC amplitude by methylphenidate are obtained only in tasks in which the subject may profit from the recruitment of additional attentional resources.

Adult↗
PubMed1981

Facial, autonomic, and subjective components of emotion: the facial feedback hypothesis versus externalizer-internalizer distinction.

Two different models have been advanced concerning the role of facial expression in the experience of emotion. The facial feedback hypothesis states that facial expressions regulate affective experience. This position has been supported by findings that experimentally induced changes in facial expressiveness produced corresponding changes in autonomic responses and self-reports of emotion. A second model posits that expressive behavior and autonomic responses are negatively related. Evidence supporting this view consists of correlational analyses showing that facially expressive people (externalizers) exhibit less autonomic arousal than do those who are not facially expressive (internalizers). In the present study, the facial feedback hypothesis and the externalizer-internalizer distinction were evaluated by manipulating facial expressiveness and measuring subsequent autonomic responses and self-reports of emotion. Results showed that higher levels of facial expressiveness were accompanied by higher levels of autonomic activity and subjective reports of affective experience. This relationship was obtained in comparisons among experimental conditions as well as correlational analyses within conditions.

Autonomic Nervous System↗
PubMed1981

A comparison of unwed pregnant teenagers and nulligravid sexually active adolescents seeking contraception.

Unwed pregnant adolescents were contrasted with nulligravid teenagers seeking contraception. Pregnant subjects were less likely to employ or plan to use contraceptives. Gravid subjects more often described their boyfriends as happy about the pregnancy and expressed a desire for a pregnancy. Nulligravid youngsters described their parents as more disapproving of their premarital sexual activity. There is a need for counseling programs, including adolescents of both sexes, and aimed at the modification of attitudes toward contraception.

Adolescent↗
PubMed1980

Effects of induced psychological stress on click and rhythm in mitral valve prolapse.

Our clinical observations suggested that anxiety accentuated the click in patients with mitral valve prolapse. In order to evaluate this systematically, a psychological stress was administered to 30 subjects--15 patients with click murmur syndrome and 15 normal controls. The phonocardiogram was recorded and the electrocardiogram were continuously monitored to assess the effects on arrhythmias. State Anxiety Inventory scores demonstrated an increase in anxiety during the psychological stress. A change in rhythm during psychological stress was noted in five of the 15 patients. No arrhythmias occurred in the control subjects during psychological stress (p less than .025). Amplitude of the click increased during psychological stress in five of the 15 patients, in four associated with arrhythmia. The only patient with auscultatory-electrocardiographic variant developed frequent, multifocal ventricular ectopics with couplets during the psychological stress. Acute psychological stress exerts important effects on the rhythm and click only in some patients with mitral valve prolapse, and may provide a mechanism for intermittence of clicks and episodes of profound unexplained arrhythmias.

Adolescent↗
PubMed1980

Effects of lithium on evoked potentials and performance during sustained attention.

Two versions of the continuous performance test (CPT) differing in complexity were administered to 15 patients with bipolar affective disorder, manic type before and after treatment with lithium. Reaction time, performance accuracy, and the late positive component (LPC) of the event related potential evoked by the task were measured concurrently. Lithium treatment decreased errors of commission on both CPT tasks, although the difference was significant only for the simpler task. Reaction time was significantly increased by lithium treatment on the more difficult CPT task, LPC amplitude to the target stimulus on the difficult CPT was significantly increased by lithium. The data are interpreted as consistent with an attention-enhancing effect of lithium, coupled with a general reduction in the tendency to respond to stimuli.

Adult↗