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Biomedical subjects

T P Zahn

Publications and source records attributed to T P Zahn.

At least 37 records · Page 2Linked to original sources
PubMed1990

Differential autonomic nervous system activity in multiple personality disorder.

The cardinal feature of multiple personality disorder (MPD) is the existence of two or more alter personality states that exchange control over the behaviour of an individual. Numerous clinical reports suggest that these alter personality states exhibit distinct physiological differences. We investigated differential autonomic nervous system (ANS) activity across nine subjects with MPD and five controls, who produced "alter" personality states by simulation and by hypnosis or deep relaxation. Eight of the nine MPD subjects consistently manifested physiologically distinct alter personality states. Three of the five controls were also produced physiologically distinct states, but these differed from those of the MPD subjects. A habituation paradigm demonstrated carryover effects at the ANS levels from one state to the next for both groups.

Adult↗
PubMed1989

Electrodermal activity in young adults at genetic risk for affective disorder.

Low electrodermal activity has been proposed as a trait marker for affective disorder. We attempted to determine if low electrodermal activity could be a genetic marker by testing subjects at genetic risk for affective disorder. High-risk subjects, 22 offspring of a parent with bipolar affective disorder, and 27 low-risk controls 15 to 25 years old had skin conductance recorded bilaterally during rest periods, presentation of 10 nonsignal tones, and performance of reaction-time and mental arithmetic tasks. There were no significant differences in skin conductance levels under any condition or in the frequency or amplitude of orienting responses to nonsignal tones. During task periods high-risk subjects showed significantly greater electrodermal activity that was lateralized to the left hand. Self-rated depression was higher in the high-risk group during task periods. The results show that low electrodermal activity is not a likely genetic marker for affective disorder but suggest that autonomic hyperresponsivity, atypically lateralized information processing, and depressive affect occur during mild stress in persons at risk for the development of affective disorder.

Adolescent↗
PubMed1988

Studies of autonomic psychophysiology and attention in schizophrenia.

Research from this laboratory over the years has found a rather consistent pattern of high baseline levels of many (but not all) indices of autonomic activity, slow adaptation, and attenuated autonomic reactivity to significant stimuli and situations in schizophrenia and that this pattern may be related to prognosis. Our studies have also shown that qualitatively similar changes occur in healthy subjects after a dose of dextroamphetamine and that certain aspects of the pattern are exaggerated in schizophrenic patients with cortical atrophy. It is hypothesized that there are specific autonomic markers for the two syndromes of schizophrenia defined by positive and negative symptoms which reflect distinct biological mechanisms. Current research seeks to determine the biological and symptomatic correlates of autonomic activity, to establish the specificity of certain autonomic markers to schizophrenia versus other major diagnoses, and to study the mechanisms and improve the assessment of attentional deficits in schizophrenia.

Arousal↗
PubMed1987

Acute autonomic nervous system effects of caffeine in prepubertal boys.

The effects of caffeine on autonomic activity were tested in 19 normal prepubertal boys. Subjects received placebo, 3 mg/kg, and 10 mg/kg caffeine in a random order (double blind) before three test sessions 48 h apart. Skin conductance (SC), heart rate (HR), and skin temperature (ST) were recorded during a rest period, a series of nonsignal tones, and a simple reaction time (RT) task. Caffeine increased the frequency of both spontaneous and elicited SC responses (SCR) under all conditions. Resting SC base level (SCL) was increased, and shorter SCR half recovery time also occurred in some periods. In contrast, caffeine decreased HR and motor activity at 3 mg/kg. Evidence of improved attention on caffeine was also obtained. The physiological effects are partially similar to the effects seen in clinical anxiety states, and they are also consistent with the physiological concomitants of good sustained attention. The profile of effects did not resemble those of dextroamphetamine in a similar population.

Attention↗
PubMed1987

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.

Adolescent↗
PubMed1987

Controllable and uncontrollable stress in humans: alterations in mood and neuroendocrine and psychophysiological function.

The authors exposed 10 healthy human volunteers to the stress of loud (100 dB) noise under controllable and uncontrollable conditions on two separate days. Subjects reported higher self-ratings of helplessness, lack of control, tension, stress, unhappiness, anxiety, and depression; had greater hypothalamic-pituitary-adrenal axis function as measured by elevations in plasma adrenocorticotropic hormone; and had higher levels of sympathetic nervous system and electrodermal activity after the uncontrollable stress condition than after exposure to controllable stress. Thus, lack of control over even a mildly aversive stimulus can produce alterations in mood as well as neuroendocrine and autonomic nervous system changes in healthy subjects.

Acoustic Stimulation↗
PubMed1986

Indices of sympathetic vascular innervation in sympathectomized patients.

We measured arterial and venous plasma catecholamines and used laser-Doppler flowmetry to measure cutaneous microcirculatory flow in the sympathectomized and in the intact limbs of 3 patients who had undergone regional sympathectomies. Venous concentrations of norepinephrine, the sympathetic neurotransmitter, exceeded arterial concentrations in the intact limbs--a normal finding--but invariably were less than arterial in the sympathectomized limbs of the same patients, both during baseline conditions and during sympathetic stimulation using tilt, standing and the cold pressor test (mean arteriovenous decrement about 40%). Arterial epinephrine levels exceeded venous levels with or without sympathectomy. Skin microvascular flow rapidly decreased during the cold pressor test and the Valsalva maneuver in the intact but not in the sympathectomized limbs, and spontaneous flow oscillations occurred in the sympathectomized limbs. The results suggest that an arteriovenous increment in plasma norepinephrine reflects local release of norepinephrine from sympathetic nerve endings, whereas removal of circulating catecholamines can occur with or without sympathetic neural impulses. Laser-Doppler flowmetry can measure reflexive sympathetically mediated responses of skin microvascular flow and so can detect sympathetic denervation. Spontaneous oscillations in this flow may not depend exclusively on oscillations in the activity of the sympathetic microvascular innervation.

Adult↗
PubMed1985

Attention dysfunction and psychopathology in college men.

Four hundred college men were screened on a measure of vigilance, the Continuous Performance Test (CPT). The individuals with good and poor attention (the upper and lower 5% of the CPT score distribution) were compared on multiple measures of psychiatric disturbance, cognition, and psycho-physiologic function. The attention dysfunction group (lower 5%) had a higher incidence of symptoms of hyperactivity both in childhood and as adults, but had no higher incidence of other psychopathology as assessed with either the Research Diagnostic Criteria or the Minnesota Multiphasic Personality Inventory. Cognitive differences between the lower and upper CPT groups, including differences on Wechsler Adult Intelligence Scale subtests, the Stroop test, reaction time, and evoked potentials, substantiated an attention dysfunction syndrome. Thus, attentional dysfunction in young adults seems more closely linked to hyperactivity than to current psychopathology.

Adolescent↗
PubMed1984

Behavioral effects of caffeine in children. Relationship between dietary choice and effects of caffeine challenge.

From a survey of 24-hour caffeine intake of 798 grade-school children (mean age, 10.3 years), 19 "high consumers" (reported intake of 500 mg/day or more) and a matched group of 19 "low consumers" were recruited for a double-blind, placebo-controlled, caffeine challenge study. Children received 5 mg/kg of caffeine twice a day or placebo for two weeks each, using a crossover design. While not receiving caffeine, high consumers had higher scores on an anxiety questionnaire and tended to have lower autonomic arousal (less frequent spontaneous skin conductance response and lower skin conductance level). While receiving caffeine, low consumers were perceived by their parents as more emotional, inattentive, and restless, while high consumers were not rated as changed. These differences cannot be attributed to tolerance, withdrawal, or subject selection, and suggest a possible physiological basis in children for dietary caffeine preference.

Adolescent↗
PubMed1984

Prazosin, a specific alpha 1-noradrenergic receptor antagonist, has no effect on symptoms but increases autonomic arousal in schizophrenic patients.

The specific alpha 1-noradrenergic antagonist, prazosin, was administered to seven schizophrenic patients in a double-blind, placebo-controlled trial. Patients showed no change in any of their psychiatric symptoms as rated by nurses on global depression and psychosis scales and by physicians on the Brief Psychiatric Rating Scale. However, they did show a significant increase in autonomic arousal as measured by changes in skin conductance. The increased autonomic arousal is probably mediated by increases in plasma norepinephrine induced by chronic prazosin treatment.

Adolescent↗
PubMed1984

Psychophysiological changes during pharmacological treatment of patients with obsessive compulsive disorder.

Twelve patients with obsessive compulsive disorder were studied with psychophysiological measures during a randomised, double-blind placebo-controlled drug trial. Significant clinical improvement followed six weeks of treatment with the tricyclic antidepressant clomipramine, but was not evident after an equal period of treatment with the monoamine oxidase inhibitor (MAOI) clorgyline. Compared to placebo, both drugs reduced skin conductance indices of baseline arousal, but only clomipramine reduced skin conductance and heart rate responses to loud tones and tonic and phasic skin conductance responses in a two-flash discrimination task. This suggests that reductions in autonomic responses to important and/or aversive stimuli may be critical to clinical improvement in obsessive compulsive disorder.

Adolescent↗
PubMed1983

Failure of hemodialysis to diminish psychotic behavior in schizophrenia: behavioral and psychophysiological evaluation.

In a double-blind sham replacement study, eight drug-free schizophrenic patients underwent 10 active and 10 sham hemodialysis for 20 weeks. At the end of the 10 active dialyses, none of the patients appeared to be improved in psychotic, affective, or social symptoms. Active dialysis was associated with a "startle" response in heart rate and skin conductance to auditory stimuli, while sham dialysis was associated with an "orienting" response. Night-recorded sleep electroencephalography was unaffected by active dialysis. Spinal fluid beta-endorphin-like immunoreactivity levels were unchanged after active treatment. The behavioral improvements reported in other studies may be related to "stress," psychotherapeutic support, spontaneous remissions, neuroleptic withdrawal, denial of symptoms, or diagnostic differences. This study did not confirm the claims for hemodialysis as a specific therapeutic intervention in schizophrenia.

Adult↗
PubMed1981

Autonomic nervous system activity in acute schizophrenia: I. method and comparison with normal controls.

Many reports of autonomic dysfunction in schizophrenia may have been influenced by the chronicity or medication status of patients, or both. This study eliminates these sources of variation. Skin conductance (SC) and heart rate (HR) base levels and activity were compared in 118 controls and 46 recently admitted, drug-free, acute schizophrenic patients during rest, 20 mild-tone stimuli, and reaction time (RT) and mental arithmetic tasks. Patients showed higher than normal HR and spontaneous SC responses but lower SC base levels. Schizophrenics showed less SC and HR reactivity to tones and RT stimuli, slow habituation of the SC orienting response, an attenuated tonic response to stress, and disproportionately more spontaneous than elicited SC activity. The findings are similar to previous results for unmedicated, chronic schizophrenics and suggest that autonomic activity in schizophrenics is determined relatively more by endogenous factors than by external stimuli.

Acute Disease↗
PubMed1981

Autonomic nervous system activity in acute schizophrenia: II. relationships to short-term prognosis and clinical state.

Autonomic nervous system (ANS) activity in acute schizophrenic patients was assessed to examine predictive relationships to clinical course. Unmedicated patients were rated on global psychopathology and tested on skin conductance, heart rate, and skin temperature during rest, a series of tones, and reaction time and mental arithmetic tasks three weeks after admission and again about three months later. On the admission tests, a pattern of ANS activity found in schizophrenics in general (high resting "arousal," slow habituation, and attenuated ANS reactivity, particularly to demanding stimuli and situations) was found in patients who were to remain clinically ill but not in patients whose recovery was more complete, especially in males. Thus, ANS activity is predictive of short-term outcome in acute schizophrenia. Minimal ANS changes accompanied clinical improvement, which suggests a "'trait" interpretation, but "state" effects cannot be completely ruled out.

Autonomic Nervous System Diseases↗
PubMed1981

Autonomic effects of dextroamphetamine in normal men: implications for hyperactivity and schizophrenia.

This study test the effects on autonomic nervous system (ANS) activity of two doses (0.25 mg/kg and 0.50 mg/kg) of dextroamphetamine in normal men. Skin conductance and heart rate were recorded during rest, tone presentation, and a reaction time task. Compared to placebo, dextroamphetamine increased both skin conductance and heart rate indices of arousal, slowed habituation, and reduced ANS responsivity selectively to more important vs. less important stimuli. The last result differs from previous findings on hyperactive and normal boys. The pattern of ANS effects closely resembles findings on drug-free schizophrenics, suggesting that it may be a matter for biologic changes occurring in amphetamine psychosis and spontaneous psychotic episodes.

Adult↗
PubMed1981

Behavioral and cognitive effects of caffeine in boys and adult males.

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.

Adult↗