Biomedical subjects

D R Cherek

Publications and source records attributed to D R Cherek.

At least 37 records · Page 2Linked to original sources

PubMed1997

Subjects with a history of drug dependence are more aggressive than subjects with no drug use history.

Aggressive responding was compared between 29 subjects with a history of substance dependence and 24 subjects with no drug use history, using the Point Subtraction Aggression Paradigm. The hypothesis was that subjects from the substance dependence history group would emit more aggressive responses than subjects with no drug use history. The substance dependence history group emitted more aggressive responses per session than the non drug using group (F(1,49) = 14.867, P = 0.032). These results are consistent with previous studies that have reported an association between aggression and drug abuse or dependence.

Adult↗

PubMed1997

College on problems of drug dependence meeting, Puerto Rico (June 1996) marijuana use and dependence.

Discoveries concerning an endogenous cannabinoid system and observations of dramatic increases in marijuana use among youth in the United States have fueled a recent increase in basic and clinical research to better understand and treat marijuana dependence. At the annual meeting of the College on Problems of Drug Dependence (Puerto Rico, 1996) a symposium 'Marijuana Use: Basic Mechanisms, Epidemiology, and Clinical Issues' reviewed a number of important areas of ongoing research that address marijuana dependence. Overviews and original research were presented regarding the development of dependence (preclinical and clinical research), motivational effects (laboratory models), the epidemiology of dependence and its development, clinical management of marijuana use among patients seeking treatment for other drugs of abuse, and treatment for adult marijuana dependence. This paper summarizes the symposium presentations and provides discussion of recent scientific developments concerning marijuana use and dependence.

Adult↗

PubMed1997

Antisocial personality disorder and aggression in recently abstinent cocaine dependent subjects.

To study the relationship between cocaine abstinence symptoms, personality, and aggression, we used the Point Subtraction Aggression Paradigm (PSAP) to measure aggression in 18 subjects admitted for the treatment of cocaine dependence. Eight subjects met criteria for antisocial personality disorder (ASPD). There was a significant correlation between presence of ASPD and frequency of aggressive responding by stepwise multiple regression. When presence of ASPD was factored out of the correlations, there was no significant relationship between aggressive responding and cocaine craving, withdrawal symptoms, amount of cocaine used, or length of time since use. These preliminary results suggest that in cocaine dependent individuals seeking treatment, current aggression is most dependent on the individual's previous aggressive behavior.

Adult↗

PubMed1997

Studies of violent and nonviolent male parolees: I. Laboratory and psychometric measurements of aggression.

Male parolees were recruited into a laboratory study to determine the relationship between their previous aggression history, psychometric measures of aggression, and behavioral measures of aggressive responding using a laboratory methodology: the Point Subtraction Aggression Paradigm. Subjects were assigned to a violent or nonviolent group based upon their criminal history. Subjects participated in sessions in which they were given three response options defined as: (1) nonaggressive responding which earned money, (2) aggressive responding which ostensibly subtracted money from another fictitious person, (This responding was defined as aggressive since it resulted in the ostensible delivery of an aversive stimulus (subtraction of money) to another person), and (3) escape which protected the subject's earnings from subtractions initiated by the other person. Results indicated that the violent subjects emitted significantly more aggressive responses than subjects in the nonviolent group. The number of aggressive responses parolees emitted was significantly correlated with most psychometric measures of aggression. This study provides external validity for our laboratory measurement of human aggressive responding, since aggressive responding was directly related to violent criminal histories.

Adult↗

PubMed1997

Studies of violent and nonviolent male parolees: II. Laboratory and psychometric measurements of impulsivity.

Males parolees were recruited into a laboratory study to determine the relationship between their previous criminal history (violent versus nonviolent), and behavioral and psychometric measures of impulsivity. During sessions, subjects were given two response options defined as: 1) an impulsive choice--small monetary reward after a short fixed delay; and 2) a self-control choice--a larger monetary reward after a variable longer delay. Based upon an extensive experimental literature in animals and humans related to delay of gratification, the degree of impulsivity was defined as the proportion of trials on which the subject selected the impulsive option. Our results indicated that the violent subjects selected the impulsive option significantly more often than the nonviolent parolees. The number of impulsive responses parolees emitted was significantly correlated with the number of aggressive responses reported in an earlier paper. This study provides support for the relationship between impulsivity and aggression among male parolees.

Adult↗

PubMed1996

Tryptophan depletion and aggressive responding in healthy males.

In order to study the effect of decreasing plasma tryptophan levels on aggressive responding in a controlled laboratory setting, we administered two doses (25 g and 100 g) of a tryptophan-free amino acid mixture to ten healthy male subjects after 24 h of a low tryptophan diet. Subjects were screened for current or past psychiatric, or non-psychiatric medical illness. Aggressive responding on a free-operant laboratory measure of aggression (the Point Subtraction Aggression Paradigm) and plasma tryptophan levels were measured before and after drinking the amino acid mixture. There was a significant increase in aggressive responding 5 h after the 100 g mixture and a significant increase in aggressive responding 6 h after the 25 g mixture compared to a baseline day when no drink was administered. There was also a significant decrease in plasma tryptophan at 5 hours after ingestion compared to baseline for both doses of amino acid mixture. This study supports the hypothesis that tryptophan depletion increases aggressive responding in healthy males in a laboratory setting, probably by decreasing brain serotonin.

Adult↗

PubMed1996

The effects of alcohol on the aggressive responding of women.

OBJECTIVE: The purpose of this study was to determine the effects of a range of alcohol doses on the aggressive responding of women. METHOD: The Point Subtraction Aggression Paradigm was used. It has two response options available to the subject: (1) point-maintained responding, emitting 100 responses on one button earned the subject 10 cents; and (2) aggressive responding, emitting 10 responses on an alternative button ostensibly subtracted 10 cents from another person also working to earn money. Aggressive responses were engendered by a random-time schedule of point loss (every 6 sec. to 120 sec.), and instructions attributed these point losses to button presses made by another fictitious subject. Ten female subjects participated, and each experienced placebos and three alcohol doses, 0.25, 0.50, and 1.00 g of 95% alcohol per kg of body weight. RESULTS: The most important finding was that the 1.00 g/kg alcohol dose produced statistically significant increases in aggressive responding relative to placebo. There was, however, a small subset of individuals whose greatest increase in aggressive responding occurred after consuming the 0.25 g/kg alcohol dose. Rates of point-maintained responding were unaffected by the 0.25 and 0.50 g/kg alcohol doses and slightly suppressed by the 1.00 g/kg alcohol dose. CONCLUSIONS: These results are important because the handful of previous studies with women have provided little evidence for increased aggression after alcohol consumption in women. These observed inconsistencies between this study and previous studies may be attributed to procedural differences, which have varied considerably across studies.

Adult↗

PubMed1995

Methylphenidate effects on a laboratory aggression measure in children with ADHD.

This study investigated the utility of the Point Subtraction Aggression Paradigm (PSAP), a computerized laboratory analog aggression measure. We measured the effects of methylphenidate (MPH) on aggressive responding in children with a DSM-III-R diagnosis of attention deficit hyperactivity disorder (ADHD), who had high ratings on the Child Behavior Checklist Aggression Factor (CBCL; Achenbach 1991). Results are reported for 6 subjects, ages 8-11 years. All were tested at baseline in an unmedicated condition, and after double-blind administration of placebo, 0.3 mg/kg of MPH, and 0.6 mg/kg of MPH. A main effect of decreased aggressive responding with MPH was found, with a dose-related change by repeated measures ANOVA (F = 6.59, df = 2.10, p = .014). Post-hoc analysis with the Tukey HSD indicated that only the 0.6 mg/kg was significantly (p < .05) different than placebo. Implications for use of the PSAP in future investigations of medications in aggressive children are discussed.

Aggression↗

PubMed1994

Serotonin and impulsive/aggressive behavior in cocaine dependent subjects.

1. 10 male cocaine dependent patients and 10 sex matched controls were administered several behavioral measures of aggression including the Buss-Durkee Hostility Inventory, and The Brown-Goodwin Life History of Aggression. 2. All subjects were also administered a buspirone neuroendocrine challenge as a measure of serotonin function. 3. The cocaine dependent subjects were significantly more aggressive than the controls. 4. There was a significant correlation between the growth hormone response to buspirone and behavioral measures of aggression in the cocaine dependent subjects, but not in the controls. 5. There was no difference in the overall growth hormone response between the controls and cocaine dependent subjects, possibly due to differences in metabolism of buspirone. 6. This study supports a role for serotonin in aggression in cocaine dependent subjects.

Adult↗

PubMed1994

Effects of ethanol on human free-operant cooperative responding.

The effects of ethanol (0.5, 0.75 and 1.00 g/kg) on human cooperative behavior were examined. Ethanol or placebo was administered 30 min before the second of five trials. During the first of two alternating schedule components, button presses were maintained by a random interval (RI) 60-s schedule of point additions to a counter marked 'Your Earnings'. During the second, Choice, component a concurrent RI 60-s schedule maintained button presses on two manipulanda. Subjects randomly assigned to the social group were instructed that they were paired with another person and could earn points working with or independently of this person. Working together, the cooperative response, simultaneously produced points on counters marked 'Other's Earnings' and 'Your Earnings'. Working independently, the independent response produced points only on the counter marked 'Your Earnings'. The other person was fictitious. The instructions for the non-social group did not mention another subject and the counter marked 'Other's Earnings' was not visible but schedule contingencies were identical to those for the social instruction group. For the social instructions group, 1.00 g/kg ethanol increased the proportion of cooperative responses and time allocated the cooperative option. For the non-social instruction group, time allocated to the topographically identical but non-social equivalent of the cooperative response decreased at the same dose. No significant between-group effects were observed following acute administration of 0.50 and 0.75 g/kg ethanol. These results suggest that the instructions established a functionally distinct social, cooperative, response which was differentially affected by ethanol.

Adolescent↗

PubMed1994

Effects of social context, reinforcer probability, and reinforcer magnitude on humans' choices to compete or not to compete.

In the first two experiments, subjects' choices to earn points (exchangeable for money) either by competing with a fictitious opponent or by not competing were studied. Buskist, Barry, Morgan, and Rossi's (1984) competitive fixed-interval schedule was modified to include a second response option, a noncompetitive fixed-interval schedule. After choosing to enter either option, the opportunity for reinforcers became available after the fixed-interval's duration had elapsed. Under the no-competition condition, points were always available after the interval had elapsed. Under the competition condition, points were available based on a predetermined probability of delivery. Experiments 1 and 2 examined how reinforcer probabilities and reinforcer magnitudes affected subjects' choices to compete. Several general conclusions can be made about the results: (a) Strong preferences to compete were observed at high and moderate reinforcer probabilities; (b) competing was observed even at very low reinforcer probabilities; (c) response rates were always higher in the competition component than in the no-competition component; and (d) response rates and choices to compete were insensitive to reinforcer-magnitude manipulations. In Experiment 3, the social context of this choice schedule was removed to determine whether the high levels of competing observed in the first two experiments were due to a response preference engendered by the social context provided by the experimenters through instructions. In contrast to the first two experiments, these subjects preferred the 60-s fixed-interval schedule (formerly the no-competition option), indicating that the instructions themselves were responsible for the preference to compete. This choice paradigm may be useful to future researchers interested in the effects of other independent variables (e.g., drugs, social context, instructions) on competitive behavior.

Adult↗

PubMed1994

The effects of smoked marijuana on progressive-interval schedule performance in humans.

In three experiments, 8 human subjects participated in a study of the effects of smoked marijuana on progressive-interval schedule performance. A two-component chained progressive-interval fixed-interval schedule of point delivery was used. In the progressive-interval component, the interval length began at 20 s and increased either geometrically or arithmetically (by either 20 s, 40 s, 80 s, 100 s, or 160 s) on each subsequent interval. After this interval elapsed, a single button press produced the fixed-interval component, with a total of five reinforcers of varying magnitude ($0.05, $0.20, or $0.40) available on a fixed-interval 20-s schedule. After the five reinforcer deliveries, the schedule returned to the initial progressive-interval component. Several relationships were found among rates of responding, postreinforcement pauses and drug administration in the progressive-interval component: (a) Postreinforcement pauses increased as the temporal requirements of the progressive-interval schedule increased; (b) rates of responding during successive progressive-interval components rapidly decreased to low rates of responding after the first few progressions; (c) postreinforcement pauses decreased systematically as dose of smoked marijuana increased; and (d) rates of responding increased after smoking active marijuana but not after smoking placebo cigarettes. Results are discussed in the context of behavioral control and relevance to other studies that have investigated the effects of smoked marijuana on schedule performance.

Adult↗

PubMed1993

Acute effects of marijuana smoking on aggressive, escape and point-maintained responding of male drug users.

Aggressive, escape and point-maintained operant responding of male marijuana smokers were measured during six 25-min sessions conducted over an 8-h experimental day. Aggressive responding ostensibly subtracted points exchangeable for money from another subject. Escape responding protected the subject's counter from point subtractions initiated by the other subject for some period of time. Aggressive and escape responding were engendered by subtracting points from the subjects and maintained by initiation of intervals free of point subtractions. Point subtractions presented to the subjects were attributed to other persons. Subjects earned points exchangeable for money on a third response option. Subjects participated in one session prior to smoking and five sessions after smoking. Subjects smoked placebo or three different potencies of active marijuana cigarettes. Marijuana smoking effects on escape responding were not significant and depended upon the frequency of provocation. Point-maintained responding was decreased after marijuana smoking. Aggressive responding was increased for the first hour after smoking and returned to placebo levels later in the day. These effects of marijuana smoking on aggressive responding are discussed in terms of subject characteristics, particularly drug use history.

Adult↗

PubMed1993

Acute and chronic alcohol tolerance in humans: effects of dose and consecutive days of exposure.

Male social drinkers received doses of either 0.75 or 1.0 g/kg body weight of alcohol over 5 consecutive days. The beverage was divided into three equal drinks, and subjects performed an eye-hand coordination motor task after each drink. The breath alcohol concentration (BAC) was assessed at each performance measurement period. Performance was also assessed when the BAC level on the descending limb of the BAC curve was similar to each of the three BAC measurements on the ascending curve. Each group developed chronic tolerance (comparing the daily postalcohol performance with the daily prealcohol performance) by the 4th day of exposure. The development of a degree of acute tolerance (assessed by comparing the performance on the ascending and descending limbs of the BAC curve) was not observed consistently in the 1.0 g/kg dose group, but was seen in more than half of the subjects in the 0.75 g/kg dose group by the 4th and 5th day of exposure.

Adult↗

PubMed1993

The effects of alcohol on free-operant aggressive behavior.

Although strong correlations between alcohol use and the frequency and intensity of social aggression have been observed in many populations, the relationship between these two events remains complex. Aggressive behavior is not always associated with alcohol or drug use, and substantial amounts of alcohol are consumed in social settings without the occurrence of violent or aggressive behavior. The relationship between alcohol and human aggressive behavior has been investigated using a free-operant procedure developed from the experimental tradition of behavioral pharmacology. The reliability of the free-operant procedure is evidenced by the similarity in experimental outcomes across laboratories using similar experimental procedures. Evidence for the validity of the procedure comes from recent studies with populations varying in histories of violent behavior, as well as from similarities in the outcome of studies using different experimental paradigms. Recent studies indicate clearly that both antecedent and consequent variables, such as the schedule of provocation and the response requirement for both aggressive and nonaggressive behavior, as well as the social context in which provocation occurs, influence the relationship between alcohol and aggressive behavior. The implications of the role of contextual factors for social policy regarding violence and alcohol use are discussed.

Adult↗

PubMed1993

Differential effects of triazolam and ethanol on awareness, memory, and psychomotor performance.

Eight normal, healthy, male volunteers each received four triazolam doses (0, 2, 4, and 8 micrograms/kg) and four ethanol doses (0, 0.25, 0.5 and 1.0 g/kg) in a double-blind, double-dummy experiment in which within-subject dose sequence was determined by a balanced Latin square design. Triazolam and ethanol produced dose-related and time-related effects on subject ratings of mood and perceived drug effects and objective measures of memory and psychomotor performance. Dose-response curves for the two drugs were not parallel, and therefore, comparisons of the two drugs were based upon comparisons of the high dose of each drug. Although the two high-dose conditions generally were not different from one another, there were differences in their relative effect sizes, which were important. The high dose of each drug produced comparable degrees of impairment on two different psychomotor tasks. Triazolam, but not ethanol, produced significant impairment on two different memory tasks. The relative effects of each drug on subject ratings of mood and perceived drug effects varied across different subject-rated measures. Only ethanol significantly increased subject ratings of alcohol strength and feeling drunk. In comparison to ethanol, triazolam tended to produce less-pronounced subject ratings of drug effect magnitude, drug liking, and estimated performance impairment. However, less-pronounced subjective effects of triazolam were not universally observed on all subject ratings. Triazolam produced greater effects on several sedative symptoms and produced comparable effects on several mood factor scales.

Adult↗

PubMed1992

Human avoidance responding with added point loss: effects of tobacco and abstinence.

Male smokers responded on a free-operant avoidance schedule with a response--point loss interval of 20 seconds and a point loss--point loss interval of 5 seconds. Unavoidable point losses were presented at variable times during the sessions. In Experiment 1 subjects were exposed to three tobacco abstinence conditions and an ad lib smoking condition. The conditions were nicotine gum, placebo gum, and no gum or cigarettes. In Experiment 2 subjects were administered tobacco smoke which delivered varying doses of nicotine. The smoke was administered by the spirometric method. Responding in each experiment was assessed during the session and also for 10 seconds following each of the unavoidable point losses. Results for Experiment 1 showed that the effect of smoke/nicotine abstinence on overall responding and for the interval following point losses differed across subjects. Results for Experiment 2 showed very little effect of acute nicotine dosing on the overall responding and varying effects on the responding during the interval following unavoidable point losses. These results are contrasted with previous research which has investigated tobacco smoke/nicotine abstinence and acute tobacco smoke dosing in experimental situations which were established as social via instructions.

Adult↗

PubMed1992

Effects of response requirement and alcohol on human aggressive responding.

Nine men participated in two experiments to determine the effects of increased response requirement and alcohol administration on free-operant aggressive responding. Two response buttons (A and B) were available. Pressing Button A was maintained by a fixed-ratio 100 schedule of point presentation. Subjects were instructed that completion of each fixed-ratio 10 on Button B resulted in the subtraction of a point from a fictitious second subject. Button B presses were defined as aggressive because they ostensibly resulted in the presentation of an aversive stimulus to another person. Aggressive responses were engendered by a random-time schedule of point loss and were maintained by initiation of intervals free of point loss. Instructions attributed these point losses to Button B presses of the fictitious other subject. In Experiment 1, increasing the ratio requirement on Button B decreased the number of ratios completed in 4 of 5 subjects. In Experiment 2, the effects of placebo and three alcohol doses (0.125, 0.25, and 0.375 g/kg) were determined when Button B presses were maintained at ratio values of 20, 40 and 80. Three subjects who reduced aggressive responding with increasing fixed-ratio values reduced aggressive responding further at higher alcohol doses. One subject who did not reduce aggressive responding with increasing fixed-ratio values increased aggressive responding at the highest alcohol dose. The results of this study support suggestions that alcohol alters aggressive behavior by reducing the control of competing contingencies.

Adult↗