Theodore P. Zahn

Psychological correlates of monoamine oxidase activity in normals.

This study replicates and extends earlier work by finding that low levels of platelet monoamine oxidase (MAO) activity correlate with sensation seeking, high ego strength, positive affect, and high leisure time activity levels, somewhat similar psychological correlates also being found for plasma amine oxidase activity. Although there are several ways in which a schizophrenia/MAO relationship may exist and still be congruent with the present data, these results pose difficulties for theories which link low MAO activity levels specifically to schizophrenia. Nothing in the present findings, however, is incongruent with the possibility of an association between low platelet MAO activity and bipolar affective disorder.

Electrodermal and heart rate orienting reactions in chronic schizophrenia

Abstract Skin resistance was recorded continuously from 52 male chronic schizophrenic patients and 20 normal males in two sessions in which either 40 visual or 40 auditory stimuli were presented at half minute intervals. Heart rate was continuously recorded in 31 patients and all controls. The patients had a higher level of arousal as indicated by a higher mean conductance level, greater number of non-specific GSRs and higher mean heart rate in one of the sessions. The most striking finding with regard to specific (orienting) electrodermal responses was their slow habituation in the schizophrenic group. This was characterized by an erratic ‘off-and-on’ pattern of responding by individual schizophrenics. Amplitudes of specific GSRs and heart rate responses were larger in the schizophrenic group. Despite the greater responsivity to the stimuli of the schizophrenics, the ratio of specific to non-specific response frequency was greater in the controls. The results are interpreted as supporting the generalization that the weaker the stimuli the greater is the autonomic responsivity of schizophrenics with respect to that of normal subjects. Several mechanisms are proposed to account for the results based on the assumptions of high arousal and fluctuating attention in the schizophrenic subjects.

Behavioral and Cognitive Effects of Caffeine in Boys and Adult Males

&NA; The behavioral and cognitive effects of single doses of caffeine (3 and 10 mg/kg) were studied using a double blind placebo‐controlled crossover design. Subjects were 19 prepubertal boys and 20 college age men. In general, children tended to show more objective effects of caffeine than did adults, with increased motor activity, increased speech rate, and decreased reaction time. Adults generally reported side effects following caffeine while children did not, and side effects were more prominent for adults with low habitual caffeine intake. Autonomic measures of arousal were similarly affected for both age groups. Caffeine had some effects that differed from those of amphetamine, indicating distinctive actions of the two stimulants.

Autonomic and behavioral effects of dextroamphetamine and placebo in normal and hyperactive prepubertal boys

The hypothesis is tested that the response to dextroamphetamine in terms of activity, attention, impulsivity, and autonomic activity is similar in normal (N) and hyperactive (H) children. Fourteen N and 15 H boys had skin conductance (SC), heart rate (HR), and finger temperature (ST) recorded during rest, presentation of eight 75- dB tones, and a reaction time (RT) procedure on three occasions: off drug (Day 1) and after ingestion (double-blind) of placebo and of .5 mg/kg dextroamphetamine. Both N and H groups showed drug effects, compared to placebo, of reduced motor activity and impulsivity, improved attention (RT), increased HR and HR slowing during RT foreperiods, and decreased ST. Both groups also had decreases in SC responsivity but in different parts of the test. Placebo compared to Day 1 produced increased activity and autonomic “arousal” but no change in RT. Stimulant drugs thus have similar behavioral and autonomic effects in both N and H boys, but the beneficial effects on behavior do not depend critically on increases in arousal.

Autonomic effects of clozapine in schizophrenia: comparison with placebo and fluphenazine.

Peripheral indicators of autonomic nervous system activity, including electrodermal activity and heart rate, were studied in 25 chronic schizophrenic patients given clinical trials of clozapine, a standard neuroleptic (fluphenazine), and placebo. The protocol included a rest period, presentation of nonsignal tones, and a reaction time task. Clozapine markedly attenuated electrodermal base levels and both phasic and tonic electrodermal responsivity compared to placebo, and somewhat less consistently compared to fluphenazine. Both electrodermal and vasoconstrictive orienting responses to tones were reduced. Elevated heart rate and reduced heart rate variability were also observed in patients taking clozapine. Many of these effects can be accounted for by clozapines anticholinergic and antihistaminic properties. There was evidence that a smaller autonomic response to the mild stress of task performance and larger heart rate responses to nonsignal tones on the alternate treatments were predictive of a good clinical response to clozapine. These results suggest that when on alternate treatments good clozapine responders show more psychophysiological signs of pathology than clinical nonresponders.

Frontal lobe lesions and electrodermal activity: effects of significance

Several studies have shown that cortical damage, especially to the right hemisphere and to frontal lobes, may attenuate skin conductance responses selectively to psychologically significant stimuli. We tested this hypothesis in 32 patients with frontal lesions, verified by computer assisted tomography and magnetic resonance imaging, and 45 healthy controls. Patients and controls were given a protocol which included a rest period, a series of innocuous tones, and a reaction time task. Patients were given a second protocol in which they viewed slides with positive and negative emotional content and neutral slides. Results showed attenuated electrodermal activity (EDA) during task instructions and smaller skin conductance responses to reaction-time stimuli in patients compared to controls but few differences under passive conditions or in orienting responses to simple tones. Patients with lateral prefrontal and paraventricular lesions were especially low in EDA in the reaction time task, and those with right and bilateral lesions in the cingulate gyrus and/or frontal operculum had attenuated EDA in both protocols. We conclude that the effects of certain frontal lesions are on the psychological response to significance which is indexed by EDA rather than directly on EDA per se.

Effects of clozapine, fluphenazine, and placebo on reaction time measures of attention and sensory dominance in schizophrenia

Two reaction time (RT) paradigms were used to study clozapines effects on sustained and selective attention compared to fluphenazine and placebo in 25 chronic schizophrenic patients. Sensory dominance was studied via simple and choice RTs to lights and tones, and on double-stimulus trials in which the two stimuli were presented simultaneously. Although 8 of the 25 patients could not perform the RT tasks when taking placebo, there were no effects of clozapine on simple or choice RT compared to placebo or fluphenazine. Subjects on all 3 treatments showed visual dominance: faster RT to lights than to tones on choice and double-stimulus trials. However, clozapine reduced this by means of a selective increase in RT to lights. Clozapine reduced failures to respond to the tone on double-stimulus trials. This was shown to be due to reductions in hallucinations. Clozapine does not generally improve attention, but it may increase the ability of schizophrenic persons to process nondominant or unattended stimuli possibly by increasing the efficiency of resource allocation. This may be partially mediated by a reduction in hallucinations.

Psychoticism and arousal: Possible evidence for a linkage of p and psychopathy

A study is described in which two postural conditions (standing, reclining) were used to induced high and low activation levels in normal Ss divided into high and low P groups ( (HP and LP). Electrodermal and heart rate (HR) measures were recorded during each of these activation conditions which included instructions, an initial rest period, a series of tones, a rtwo-flash threshold task and a final rest period. It was found that HP Ss tended to display significantly lower automatic arousability and poorer two-flash performance while undergoing the low activation (Recline) condition. There was a reliable tendency for HP Ss to evidence significantly slower recovery and rise times and to manifest significantly lower response criterion and sensory sensitivity. They also manifested a near significantly lower mean HR than LP Ss. The performance of HP and LP groups was compared to findings reported previously for schizophrenics and psychopaths for these tasks. It was posited that the performance of the HP Ss suggests that psychoticism may be more nearly akin to psychopathy than to schizophrenia.

Reaction time indices of attention deficits in boys with disruptive behavior disorders.

Boys with diagnoses in the disruptive behavior disorder (DBD) spectrum and normal controls were tested in two reaction time (RT) experiments. In Experiment I simple warned RT was measured and the length and regularity of the preparatory intervals were varied in order to study sustained attention in the sense of preparation. With age and IQ controlled, DBD boys had slower and more variable RT overall than controls and showed generally more pronounced effects of variations in the length and sequence of the preparatory intervals. The results suggest that DBD boys are subject to lapses of attention which are increased by a relatively long preparatory interval, and that they have a particular problem with temporal uncertainty. In Experiment II some aspects of selective attention were studied in a paradigm in which stimulus modality uncertainty and response selection were varied. DBD boys showed greater effects of modality uncertainty but not response selection than controls. No differences between subdiagnoses within the DBD spectrum could be demonstrated.

Autonomic nervous system effects of acute doses of caffeine in caffeine users and abstainers.

The effects of caffeine on autonomic nervous system (ANS) activity were tested in 20 adult males who were either high or low consumers of caffeine. Subjects received placebo, 3 mg/kg, and 10 mg/kg of caffeine in a counterbalanced order (double-blind) before 3 test sessions 48 h apart. Skin conductance (SC), heart rate, and skin temperature (ST) were recorded during a rest period, a series of non-signal tones, and a simple reaction time task. Caffeine increased resting electrodermal activity (EDA) and increased the SC orienting response to the first non-signal tone, but reduced the increase in tonic EDA due to task performance. ST was reduced by caffeine in both rest and task periods. Increases in nervous/jittery ratings occurred after caffeine ingestion, but task performance was not affected. Low consumers of caffeine showed significantly more ANS responsivity than high consumers under all conditions and did not differ in ANS, behavioral, or subjective effects of caffeine. The acute physiological changes are partly similar to those reported for patients with anxiety disorders, suggesting a possible role of ANS activity in mediating the anxiogenic effects of caffeine. Effects of user status may reflect a predisposing trait, but an effect of chronic caffeine use on ANS sensitivity cannot be ruled out.