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Biomedical subjects

D R Cherek

Publications and source records attributed to D R Cherek.

At least 19 recordsLinked to original sources
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↗
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↗
PubMed1991

Human aggressive responding during acute tobacco abstinence: effects of nicotine and placebo gum.

Aggressive and point maintained operant responding of heavy nicotine dependent male tobacco smokers were measured during five 25-min sessions conducted over an 8-h period. Responding under three tobacco abstinence conditions was compared to responding during a baseline condition of ad libitum smoking of the subject's preferred brand of cigarettes. The three tobacco abstinence conditions were: (1) placebo gum, (2) nicotine gum or (3) no gum. Under placebo and nicotine gum conditions, subjects were given two pieces of placebo or 2 mg nicotine gum to chew for 30 min prior to each session. Expired air carbon monoxide (CO) levels were measured at the end of each session to monitor smoking under baseline conditions and compliance with nonsmoking requirements under abstinence conditions. Aggressive responding was increased in no gum and placebo gum conditions, with the highest frequency of aggressive responding occurring under no-gum conditions. Aggressive responding during nicotine gum conditions did not differ from baseline ad libitum tobacco smoking. Point maintained responding was either not affected or decreased under placebo and no-gum conditions. These results provided objective data consistent with clinical reports of increased irritability among dependent tobacco smokers during acute tobacco abstinence.

Adult↗
PubMed1991

Effects of triazolam on human aggressive, escape and point-maintained responding.

Placebo and triazolam (0.125, 0.25 and 0.5 mg/70 kg of body weight) were administered to male subjects under double-blind conditions prior to experimental sessions which provided three operant response options. These options were: 1) responding maintained by the presentation of points exchangeable for money, 2) responding which ostensibly resulted in the subtraction of points from a fictitious person was termed aggressive since this responding resulted in the delivery of an aversive stimulus to another person, and 3) responding which ostensibly protected the subject's point counter from subtractions initiated by the other person and was termed escape. Aggressive and escape responding were initiated by subtracting points from the subject. Point subtractions were attributed to the other person. Aggressive and escape responding were maintained by initiation of provocation-free intervals (PFI), during which no further point subtractions were presented. Triazolam produced dose-dependent decreases in point-maintained and escape responding. The effects of triazolam on aggressive responding varied across subjects.

Adult↗
PubMed1990

Effects of acute administration of diazepam and d-amphetamine on aggressive and escape responding of normal male subjects.

Normal males participated in sessions providing two operant response options and were administered either diazepam (study I and II) or d-amphetamine (study II). The acute effects of diazepam on human aggressive responding, which ostensibly subtracted points from another person, were determined in study I. Study II was conducted to determine the extent to which social context and response consequence influenced diazepam (study I) and d-amphetamine (previous research) effects on aggressive responding. In study II, the other response option was escape responding which protected the subject's counter from point losses. Aggressive and escape responding were engendered by subtracting points from the subject's counter, and maintained by initiation of intervals free of point loss. Point subtractions were attributed to the other person (study I) or to a machine (study II). Responding to accumulate points exchangeable for money was available in both studies. Acute diazepam administration decreased aggressive responding in most subjects (study I), slightly increased escape responding (study II), and decreased responding to accumulate points. In study II, d-amphetamine increased both escape responding and responding to accumulate points. The effects of d-amphetamine and diazepam were altered by the instructed source of point loss.

Aggression↗
PubMed1990

Benzodiazepine-induced impairment of matching-to-sample performance in humans.

The effects of benzodiazepines on a visual pattern matching-to-sample (MTS) task were examined in nine healthy male volunteers. The MTS task employed randomly generated checkerboard-like stimuli presented on a video display. The sample and two comparison stimuli were simultaneously presented. Nonmatching comparison stimuli were randomly generated to be 3.125, 6.25, 12.5, 25.0, 37.5, or 50.0 percent different from the sample. Subjects responded on left or right button manipulanda to identify the matching comparison stimulus. The nonmatching stimulus condition was maintained constant for a 60-sec component and the percentage difference of the nonmatching stimuli was systematically varied across multiple components. The effects of triazolam (2.25-9.0 micrograms/kg) and lorazepam (7.5-45 micrograms/kg) were examined in a within-subjects, double-blind, placebo-controlled study. Under placebo conditions, response rates and accuracy were a positive function of the nonmatching stimulus discriminability. Triazolam produced dose-related decreases in response rate at nonmatching stimulus conditions greater than or equal to 25%. Only the 9.0 micrograms/kg dose of triazolam decreased accuracy and this occurred across all nonmatching stimulus conditions. Lorazepam effects were qualitatively similar but less robust than those of triazolam.

Adult↗
PubMed1990

The effects of codeine on human aggressive responding.

Ten healthy male research subjects received placebo, 25, 50 and 75 mg/70 kg of codeine in a controlled laboratory setting. During each session subjects had two response options. The non-aggressive response option was maintained by points exchangeable for ten cents. The aggressive response option ostensibly subtracted a point from the subject's fictitious partner. Aggressive responding was engendered by point subtractions attributed to a fictitious partner. Codeine did not significantly alter the frequency of monetarily reinforced, nonaggressive, responding. Aggressive responding was significantly increased at the 50 mg/70 kg dose of codeine. The frequency of aggressive responses during the placebo sessions preceding administration of the first codeine dose were significantly and positively correlated with scores on the Buss-Durkee Hostility Scale. Aggressive responding increased for four of five subjects scoring below the median on the Buss-Durkee Hostility Scale at the 50 mg/70 kg dose; while administration of 50 mg/70 kg increased aggressive responding of one subject who scored above the median. Aggressive responding for both groups of subjects was unaffected by the 75 mg/70 kg dose.

Administration, Oral↗
PubMed1990

Human aggressive responses maintained by avoidance or escape from point loss.

During 50-min sessions, 6 male human subjects could press either Button A or Button B available as nonreversible options. Button A presses were nonaggressive responses and earned points according to a fixed-ratio 100 schedule. Prior to the experiment subjects were instructed that every 10 (fixed-ratio 10) Button B presses (aggressive responses) subtracted a point from a fictitious 2nd subject. A random-time schedule of point loss was used to engender aggressive responding. The instructions attributed these point losses to the Button B presses of the subject's fictitious partner. Aggressive responding either escaped or avoided point loss by initiating an interval free of point loss. The duration of the interval was varied systematically across sessions. Avoidance contingencies maintained a high rate of aggressive responding over 30 sessions in the absence of point loss. Escape contingencies also maintained aggressive responding across sessions, with rates of aggressive responding corresponding to rates of point loss.

Adult↗
PubMed1989

Effects of nicotine gum and tobacco smoking on human avoidance responding.

Three male smokers were exposed to a free-operant avoidance schedule in which a lever press postponed a point subtraction on a counter for twenty seconds. Subtractions were scheduled to occur every 5 seconds in the absence of lever presses. Prior to each experimental session the subject was administered varying amounts of nicotine via either chewing nicotine gum or smoking low or high nicotine yield cigarettes. Smoking cigarettes resulted in increased avoidance responding relative to baseline nonsmoking rates. Chewing nicotine gum did not produce changes in avoidance responding, however, nicotine blood levels produced by chewing nicotine gum were similar to levels produced by smoking cigarettes. The differential responding determined by route of nicotine administration is discussed and the implications for use of nicotine gum as an adjunct for smoking cessation is addressed.

Avoidance Learning↗