The effect of d-amphetamine on short-term memory for time in pigeons

The effect of d-amphetamine on pigeons' perception and short-term memory of time was investigated within a delayed symbolic matching to sample paradigm in which pigeons were rewarded for choosing one color after a 1-sec sample and another color after a 5-sec sample. On trials with no delay between sample offset and onset of the choice phase, d-amphetamine produced a bias toward choosing the color that was correct after long samples, suggesting that the birds overestimated the sample durations under amphetamine. With a 20-sec retention delay, d-amphetamine lowered choice accuracy to chance level, suggesting that it impaired the bird's short-term memory for sample durations. It was postulated that an amphetamine-induced increase in the rate of perceptual processing could mediate the effects of amphetamine on both time perception and memory.

Properties of the internal clock

Evidence has been cited for the following properties of the parts of the psychological process used for timing intervals: The pacemaker has a mean rate that can be varied by drugs, diet, and stress. The switch has a latency to operate and it can be operated in various modes, such as run, stop, and reset. The accumulator times up, in absolute, arithmetic units. Working memory can be reset on command or, after lesions have been created in the fimbria fornix, when there is a gap in a signal. The transformation from the accumulator to reference memory is done with a multiplicative constant that is affected by drugs, lesions, and individual differences. The comparator uses a ratio between the value in the accumulator (or working memory) and reference memory. Finally, there must be multiple switch-accumulator modules to handle simultaneous temporal processing; and the psychological timing process may be used on some occasions and not on others.

The phenomenological structure of drug-induced ego states. II. Barbiturates and sedative-hypnotics: phenomenology and implications

Empirically derived descriptions of experiential states, induced by heavy, chronic consumption of drugs, provide valuable information for treatment personnel as well as for scientists studying drug abuse or pharmacology. A 7-year program of research has studied persons committed to heavy, long-term use of several prominent substances of abuse. This report results from that research and provides a phenomenological description of the psychological state induced by heavy, chronic use of barbiturates and sedative-hypnotics. Interview, Q-sort and semantic differential data indicate the barbiturate state is intensely unpleasant: a state in which users lose desired characteristics, take on undesired characteristics, engage in self-destructive acts, and emerge in worse condition than before entering it. Explaining why people choose to enter such a state is difficult. Several theoretical alternatives for doing so are considered. Psychotherapy with these individuals must deal with the theme of abandonment/rejection that permeates their lives and with the diffuse hostility, expectations of failure and defeat, self-destructive tendencies, and feelings of hopelessness that they display. Suggestions are presented for treatment of individual cases.

Drug-induced ego states. I. Cocaine: phenomenology and implications

The ego state experienced by chronic users of cocaine is described in terms of sensorimotor functioning, cognitive functioning, emotionality, spatiality , temporality , causality, and materiality . At low use levels the state is pleasurable, but at high levels fear, anxiety, and paranoia increase, and ultimately reality contact breaks down. Q-sort, Semantic Differential, and other data suggest that low-level users take cocaine to overcome personal insecurities and relieve boredom. Heavy users take it to support overvaulting ambitions and intense strivings for self-sufficiency. Psychotherapy with such persons must deal with their counterdependency , anger, and despair, and with their underlying sense of betrayal . These persons have unacknowledged needs for spiritual experience that must be dealt with openly. A description of persons most vulnerable to heavy use of cocaine is provided, and recommendations for research and social policy are presented.

Properties of the internal clock

Evidence has been cited for the following properties of the parts of the psychological process used for timing intervals: The pacemaker has a mean rate that can be varied by drugs, diet, and stress. The switch has a latency to operate and it can be operated in various modes, such as run, stop, and reset. The accumulator times up, in absolute, arithmetic units. Working memory can be reset on command or, after lesions have been created in the fimbria fornix, when there is a gap in a signal. The transformation from the accumulator to reference memory is done with a multiplicative constant that is affected by drugs, lesions, and individual differences. The comparator uses a ratio between the value in the accumulator (or working memory) and reference memory. Finally, there must be multiple switch-accumulator modules to handle simultaneous temporal processing; and the psychological timing process may be used on some occasions and not on others.

Cerebral function in hyperthyroid patients. Psychopathology, psychometric variables, central arousal and time perception before and after thyreostatic therapy

Psychopathology, psychometric variables, central arousal and time experience were studied in 30 hyperthyroid female outpatients. While these patients could be significantly discriminated in several of the above-described measures during the acute state of the disease, the intergroup differences disappeared after thyreostatic therapy. The thyroxine level was correlated with elevated beta-activity and the latter with variables of psychopathology and time experience. Hormonal dysbalance in hyperthyroidism is discussed as a biological substrate for neurophysiological changes which in turn causes deterioration in mood and behavior.

A mode control model of counting and timing processes

The similarity of animal counting and timing processes was demonstrated in four experiments that used a psychophysical choice procedure. In Experiment 1, rats initially learned a discrimination between a two-cycle auditory signal of 2-sec duration and an eight-cycle auditory signal of 8-sec duration. For the number discrimination test, the number of cycles was varied, and the signal duration was held constant at an intermediate value. For the duration discrimination test, the signal duration was varied, and the number of cycles was held constant at an intermediate value. Rats were equally sensitive to a 4:1 ratio of counts (with duration controlled) and a 4:1 ratio of times (with number controlled). The point of subjective equality for the psychophysical functions that related response classification to signal value was near the geometric mean of the extreme values for both number and duration discriminations. Experiment 2 demonstrated that 1.5 mg/kg of methamphetamine administered intraperitoneally shifted the psychophysical functions for both number and duration leftward by approximately 10%. Experiment 3 demonstrated that the magnitude of cross-modal transfer from auditory signals to cutaneous signals was similar for number and duration. In Experiment 4 the mapping of number onto duration demonstrated that a count was approximately equal to 200 msec. The psychophysical functions for number and duration were fit with a scalar expectancy model with the same parameter values for each attribute. The conclusion was that the same internal mechanism is used for counting and timing. This mechanism can be used in several modes: the "event" mode for counting or the "run" and the "stop" modes for timing.

Selective adjustment of the speed of internal clock and memory processes

Four experiments studied the scaling of time by rats. The purpose was to determine if internal clock and memory processes could be selectively adjusted by pharmacological manipulations. All of the experiments used a temporal discrimination procedure in which one response ("short") was reinforced following a 2-sec noise signal and a different response ("long") was reinforced following an 8-sec noise signal; unreinforced signals of intermediate duration were also presented. The proportion of "long" responses increased as a function of signal duration. All drugs were administered intraperitoneally (ip) and their effect on clock or memory processes was inferred from the observed pattern of change in the point of subjective equality of the psychophysical functions under training and testing conditions. Experiment 1 demonstrated that methamphetamine (1.5 mg/kg) can selectively increase clock speed and that haloperidol (.12 mg/kg) can selectively decrease clock speed. Experiment 2 demonstrated that footshock stress (.2 mA) can selectively increase clock speed during continuous administration but leads to a decrease in clock speed below control values when the footshock is abruptly terminated. Experiment 3 demonstrated that vasopressin (.07 pressor units/kg) and oxytocin (.02 pressor units/kg) can selectively decrease the remembered durations of reinforced times, which suggests that memory storage speed increased. Experiment 4 demonstrated that physostigmine (.01 mg/kg) can selectively decrease the remembered durations of reinforced times and that atropine (.05 mg/kg) can selectively increase these remembered durations, which suggests that memory storage speed was differentially affected. The conclusion is that internal clock and memory processes can be dissociated by selectively adjusting their speed of operation and that these changes can be quantitatively modeled by a scalar timing theory.

The differential effects of haloperidol and methamphetamine on time estimation in the rat

Forty rats were trained to make a left lever response if a signal (white noise) was 2.5s and to make a right lever response if the signal was 6.3s. When seven intermediate signal durations, to which responses were not reinforced, were randomly interspersed the probability of a right-lever ('long') response increased as a function of signal duration. Methamphetamine shifted this psychometric function leftward and decreased its slope: haloperidol also decreased the slope but shifted the function rightward. A combination of haloperidol and methamphetamine led to a function similar to the saline control function. The leftward shift probably reflects an increase in the speed of an internal clock, and the rightward shift probably reflects a decrease in its speed. Since methamphetamine releases several catecholamines, including dopamine, and haloperidol blocks dopamine receptors, it is plausible that the horizontal location of the psychometric function (the speed of the clock) is related to the effective level of dopamine.

Drug-alcohol interactions on psychomotor skills: zopiclone and flunitrazepam

Interaction between alcohol and zopiclone or flunitrazepam as well as the residual effects of both these hypnotics were studied in 20 normal male volunteers who received each 3 of 6 different drug and drink combinations according to a balanced incomplete block design as follows: placebo, zopiclone (7.5 mg), or flunitrazepam (2 mg) was administered double-blind in identical capsules at 23.00 h, and 0.5 g/kg body weight of alcohol or placebo alcohol was given at 08.30 h the following morning. Psychomotor skills of the volunteers were measured before drinking and 30 min, 1.5 h and 2.5 h after it. As compared with placebo, zopiclone had no residual effects, while flunitrazepam had some effects on standing steadiness, tracking, and flicker recognition. Alcohol alone had a non-significant effect on skills, and the combination zopiclone plus alcohol behaved as alcohol alone. Flunitrazepam plus alcohol impaired significantly standing steadiness, tracking, and reactive skills when compared with all other treatments. Time anticipation and hand and foot proprioception were not affected by any treatment. The results suggest that flunitrazepam, unlike zopiclone, has residual effects and interacts with alcohol in the morning following overnight ingestion of the drug.

Effects of piribedil on schedule-controlled responding of the pigeon

The effects of piribedil were studied in pigeons responding under a multiple fixed-ratio 30-response, fixed-interval 5-minute schedule of food presentation. Piribedil (0.03-10 mg/kg) increased responding under the fixed-interval component to a much greater extent than d-amphetamine (0.3-3 mg/kg) did. The rate-increasing effects of piribedil on fixed-interval responding were attenuated by haloperidol (0.003 and 0.03 mg/kg), alpha-methyl-p-tyrosine (50, 100 and 200 mg/kg), and tetrabenazine (10 and 30 mg/kg). These drug interactions suggest that piribedil acts as an indirect-acting, dopaminergic agonist to produce its rate-increasing effects on schedule-controlled responding in the pigeon.

Change in effects from marijuana: a five- to six-year follow-up

A five- to six-year follow-up study of 97 regular marijuana users in a large Midwestern city showed that the effect of marijuana intoxication remained fairly stable over time. However, continued use of the drug was associated with a decrease in pleasurable effects. Undesirable effects persisted but apparently did not discourage continued use. Decreases found in some undesirable effects (tachycardia, lightheadedness, and dry mouth) raised the possibility that some degree of tolerance had developed.

Remote memory during marijuana intoxication

The effects of acute marijuana intoxication on remote memory and new learning were assessed. To test for the effects of marijuana on remote memory, titles of one-season television shows, aired up to 14 years previously, were used in three tests measuring recognition, temporal judgement and detailed recall of facts from the shows. Marijuana did not affect remote memory in comparison to placebo. The effects of marijuana on the learning of a word list were also tested. Marijuana significantly impaired new learning at the same time that remote memory was unaffected.

The generality of the stimulus-binding hypothesis across drinking behavior and task performance in alcoholics

This experiment investigated the validity of applying the stimulus-binding hypothesis of obesity to conceptualize drinking and task performance behaviors in alcoholics. Twenty alcoholics and 12 nonalcoholics participated in two counterbalanced experimental sessions. One session involved an assessment of subjects' voluntary consumption of preferred and nonpreferred nonalcoholic beverages. The other session involved their performance of four tasks that involved or manipulated the presence of salient external cues. The prediction of heightened externality in alcoholics was supported on the beverage consumption measures and was marginally supported on the task performance measures. The results are discussed in terms of their implications for models and treatments of alcohol problems.

Cannabis and sex: multifaceted paradoxes

At the present level of ignorance about sexuality and cannabis, what rational position can be adopted? First, it must be recognized that even without cannabis, current involvement in sex-related activities may well have been called "promiscuous" by a preceding generation or two. The general loosening of morality, the erosion of family, church and other authoritarian controls, The Pill, antibiotics and other recent developments have contributed to current casual attitudes. Although one may not perceive it, counterculture beliefs have had their impact on the dominant culture. Marijuana has some enhancing effect upon sexual proceedings for some individuals. It may be sexually evocative and gratifying. Nonspecific factors play an important role in this matter. Opposite effects also occur, and an endocrinologic basis for actual diminution of drives and potency may exist. The final paradox is that cannabis' employment for sexual arousal is predominantly an activity of young adults. The older age groups most in need of sexual support and assistance are less frequently involved in its use. It is unclear why this dichotomy between need and utilization exists.

[Effects of repeated administration of pyrithiamine and oxythiamine on timing behavior in rats (author's transl)]

Male Wistar rats were trained to hold down a lever for reinforcement with food pellets. No external stimulus signalled the end of the required duration. The minimum duration required was gradually raised to, and fixed at, 2 seconds. This was achieved in about 1-2 months. At the end of pre-drug training, the average response duration was 2.06 +/- 0.03 seconds in a daily 10-minute session. Daily injections of pyrithiamine, a thiamine analog which causes a rapid depletion of the brain vitamin, were given after the daily experimental session. The average response duration increased significantly by the 8th day of pyrithiamine treatment (2 mg/kg/day), without altering any other parameters examined. This pyrithiamine-induced change in duration, which was gradually diminished after the 14-day drug period, could be reversed with thiamine (2 doses of 5 mg/kg). On the other hand, oxythiamine did not cause an increase in duration over the 14 days of daily injections. The results obtained suggest that pyrithiamine exerted significant effects on discrimination of duration or internal timing mechanism in rats at the doses used, perhaps because of the depletion of the brain vitamin.

Methyl chloride and diazepam effects on performance

Human behavioral effects resulting from the ingestion of an average dose of diazepam and from 3 h of inhaling either 100 ppm or 200 ppm of methyl chloride (MeCl) were studied in the laboratory. Each of 56 volunteers was randomly assigned to one of six groups comprising the combinations of diazepam and placebo and one of the two levels of MeCl plus control. Each individual was tested in an environmental room on three tasks involving components of eye-hand coordination, mental alertness, and time discrimination. Both pretreatment and treatment data were obtained. Diazepam produced a significant 10% impairment in task performance, whereas the effect of 200 ppm of MeCl was marginally significant (average performance impairment of 4.5%). When the two agents were combined, total impairment was equal to the sum of the individually induced losses. Large interindividual differences in breath and blood levels were found for MeCl.

Methamphetamine and time estimation

Three experiments were conducted to determine the effect of methamphetamine on the performance of rats in two timing tasks. When food sometimes followed the first response after T sec of a signal, the response rate increased to a peak near T sec and then declined. Methamphetamine decreased the time of the peak (Experiments 1 and 2). When one response (called a "short response") was reinforced following a short signal and a different response (a "long response") was reinforced following a long signal (where the short and long signals were 1 and 4, 2 and 8, or 4 and 16 sec), the probability of a long response increased as a function of signal duration. The point of indifference (50% long response) occurred near the geometric mean of the extreme durations, and methamphetamine decreased the point of indifference by about 10%. These results suggest that methamphetamine increases the speed of an internal clock used by rats in time discrimination tasks.

Effects of alcohol on velocity perception: I. Stimulus velocity and change in performance over time

17 subjects who were required to estimate the time of arrival at a target of a moving light overestimated less after alcohol treatment than after placebo.

Methadone-induced attenuation of the effects of delta 9-tetrahydrocannabinol on temporal discrimination in pigeons

Pigeons responded under a discrete trial procedure in which they were required to peck one of two keys depending on the duration of a conditional stimulus (general illumination of the experimental chamber). Correct choices (red key after a 4-sec stimulus; green key after an 8-sec stimulus) resulted in the intermittent presentation of food; incorrect choices resulted in a darkened chamber. Intermediate durations (probe stimuli) were also presented occasionally. The effects of tetrahydrocannabinol (THC; 0.06-0.50 mg/kg) and repeated methadone injections (2-20 mg/kg/day) were assessed alone and in combination. THC resulted in a dose-dependent decrease in accuracy with the greater effect on long-duration trials. Repeated methadone alone resulted in a decrease in accuracy only when the methadone dose was changed. High doses of methadone (6 and 20 mg/kg/day) resulted in either a complete (0.25 mg/kg of THC) or partial (0.50 mg/kg of THC) attenuation of effects of THC on temporal discrimination accuracy as compared to a low methadone dose (2 mg/kg/day) or THC alone. The results suggest the possibility of cross-tolerance or antagonism between methadone and THC.

Sensitivity of some human cognitive functions to effects of methamphetamine and secobarbital

Sternberg's memory scanning task, Buschke's selective reminding task, and a time production task were given to 18 male subjects after they had received 10 mg of methamphetamine, 100 mg of secobarbital and placebo on separate days. Time production and learning that involved storage and retrieval of information in long-term memory were most sensitive to drug effects. Other measures of learning and memory scanning performance were not affected by either drug.

Effects of dimepramine fumarate on physiological and cognitive behaviors of Parkinson patients

Nine patients 55 to 74 years old with Parkinson's disease were tested before and after treatment with 50 to 225 mg dimepramine fumarate (CIBA G-31406) for about three weeks daily in order to determine the drug's effects on electrodermal responsiveness to a series of unpredictably occurring loud sounds. Twelve control subjects were tested and retested with the same procedure. In addition, the Parkinson patients received a number of cognitive tests before and after drug treatment. Results indicated that the drug tends to decrease autonomic arousal responses as measured by resting conductance levels, number of fluctuations in skin conduction per minute, orienting response, and habituation rate. These decreases in measures of arousal generally were accompanied by lowered performance scores on several tests of memory and temporal discrimination ability.

Effects of trifluoperazine, chlorpromazine, and haloperidol upon temporal information processing by schizophrenic patients

Healthy controls, unmedicated, actively symptomatic schizophrenics, and similar patients undergoing treatment with either trifluoperazine, chlorpromazine, or haloperidol were studied with tests of temporal discrimination and measures of transmitted information shown previously to be sensitive to various kinds of brain dysfunction, including haloperidol effects in a nonpsychotic population. Variations in psychophysical method, cognitive load, discrimination complexity, and sense-mode conditions permitted representative sampling of the temporal processing. Untreated, actively psychotic patients showed no impairment of temporal processing while all three antipsychotic medications were associated with significant deficit; trifluoperazine and haloperidol produced the most deficit, with chlorpromazine in the middle between the higher potency drugs on the one hand and unmedicated patients and healthy controls on the other.

Lithium effects on time estimation and mood in manic-melancholic patients. A study of diurnal variations

Behavioural measurements of time experience and phenomenological self-ratings of mood-variations (Beecher's Mood Scale) have been carried out at night and on the following morning in a group of lithium-treated patients, in a group of psychiatric patients not given lithium, and in an untreated group of healthy subjects. In all the groups investigated the internal "clock" was slower in the morning than in the night. The results indicated that the internal "clock" in lithium-treated patients was slower than in the two other groups, but only at night. Mood variations from night ot morning were observed in all three groups. The group of lithium-treated patients had fewer complaints as to self-report of mood-variations compared with the other groups.

Dissociation of autonomic and cognitive effects of THC in man

Intravenous THC, 30--44.8 microgram/kg, was administered to four subjects. Each received THC on four occasions preceded by either i.v. saline, 0.04 mg/kg atropine sulfate, 0.2 mg/kg propranolol, or both drugs together. Heart rates, subjective intoxication and symptom ratings, time productions, and EEG activity were measured. In the absence of autonomic blocking drugs, THC produced characteristic tachycardia, subjective intoxication, and EEG effects. After combined autonomic blockade, THC had no effect on heart rate, while subjective and EEG changes remained as intense. These findings argue against the hypothesis that the subjective and EEG effects of THC are mediated by autonomic receptors or by interoception of peripheral autonomic actions of THC.

Drugs and the discrimination of duration

The effects of lysergic acid diethylamide (LSD), d-amphetamine (AMP), chlorpromazine (CPZ), and the most active isomer of marihuana (delta9 - THC) on timing behavior were analyzed with a two-choice, discrete trial procedure in which pigeons were trained to discriminate visual stimuli that differed with respect to duration ('long' vs. 'short'). LSD (0.01, 0.04, 0.16 mg/kg) decreased response speed (increased latency), but otherwise had no significant effects on performance of the discrimination. d-Amphetamine (1.0, 2.0, 4.0 mg/kg) increased perseveration of 'spatial bias' and, at a dose of 4.0 mg/kg, lowered response speed. This compound did not significantly alter accuracy (percentage correct). CPZ (7.5, 15.0, 30.0 mg/kg) significantly decreased accuracy and, at a dose of 30.0 mg/kg, significantly lowered speed; THC also decreased accuracy and lowered speed. Neither CPZ nor THC significantly altered perseveration.

Psychomotor changes during initial day of benzodiazepine medication

1 The detracting psychomotor effects of diazepam (5 mg three times daily) and clobazam (an investigational 1,5-benzodiazepine) were compared with placebo effects over the course of the initial day of medication. Tests were administered at hourly intervals and the data were analyzed from the standpoint of contrasts at each session and from the standpoint of trends that accrued during the course of the day. 2 It is concluded that among normal volunteers diazepam 5 mg three times daily may be near the threshold for detracting psychomotor consequences during the initial day and that clobazam seems to be without detracting consequences and may have some enhancing effects.

Carbon monoxide and human time discrimination: failure to replicate Beard-Wertheim experiments

Beard and Wertheium described a dose-related deficit in human time perception during low level CO exposure. Two other laboratories were unable to replicate this finding, although methodological differences could explain these failures. This study more precisely repeated the original experiment, but failed again to obtain any CO-related deficit. The bulk of evidence, therefore, does not indicate any adverse effect of low level CO exposure on time perception in healthy young adults.

Effects of benzodiazepines on psychomotor performance

1 The literature relating to the effects of benzodiazepines on psychomotor performance is critically reviewed. 2 The multiple and diverse psychomotor tests used are assessed according to their ability to demonstrate differences between drugs. 3 Three general conclusions are: (1) The speed with which simple acts of a repetitive nature are performed may be impaired by benzodiazepines. (2) learning and immediate memory will also be impaired. (3) there is relatively little indication that well established higher mental faculties are adversely involved.

Methadone maintenance: an assessment of potential fluctuations in behavior between doses

Thirty methadone maintenance outpatients were measured 1 and 25 hours after ingestion of methadone on auditory threshold, distance perception, simple and differential reaction time, time perception, attention span, and short-term memory. The results revealed a small but statistically significant difference between the two tests for distance perception. In addition, treatment interacted with preparatory interval on differential reaction time and with sex on attention span.

Effects of tobacco, time on task, and stimulus speed on judgments of velocity and time

16 college students were required to predict the time of target arrival for a stimulus apparently moving horizontally to a point of occlusion and to reproduce the time interval the stimulus was present under smoking and no-smoking conditions. Tobacco resulted in underestimations of velocity and time judgments particularly in the early stage of the task and for the slowest stimulus speed.

Effects of d-amphetamine on temporal and spatial discrimination in rats

Rats were trained to lever-press for food reinforcers on a multiple schedule that had a fixed-interval (FI) and a differential reinforcement of low rate (DRL) component. Illumination of a stimulus light above the right-hand lever indicated that responses on this lever would be reinforced according to a FI 60-s schedule while responses on the left-hand lever were without programmed consequences. However, when the light above the left-hand lever was illuminated only responses on this lever were reinforced according to a DRL 15-s schedule. When the behaviour of the subjects had been brought under schedule control so that characteristic patterns of FI and DRL responding were emitted and there were relatively few responses on the incorrect levers, the effects of several doses of d-amphetamine (0.25, 0.5, 1.0, and 2.0 mg/kg) were assessed. The drug increased preference for responding on the right-hand lever. Thus, as dosage increased performance tended towards a constant high rate of responding on the right-hand lever throughout a session, with a much lower response rate on the left-hand lever. This result emphasises that the behavioural effects of drugs depend not only on patterns of ongoing behaviour but also on the context in which this behaviour occurs.

Some psychological correlates of long-term heavy cannabis users

Fifty persons who had all been heavy cannabis users for a long time were given psychological tests measuring psychomotor, perceptual and other variables. Half of these persons were "Charas" smokers, half "Bhang" drinkers. The duration of cannabis use was 4--10 years, with an average daily dose of 150 mg tetrahydrocannabinol. A matched control group of twenty-five persons were given the same tests. Compared with this group, the cannabis users were found to react more slowly, to be poorer in concentration and time estimation, to have higher neuroticism and greater perceptuo-motor disturbance. The higher neuroticism and greater perceptuo-motor disturbance. The Charas smokers were the poorest performers and also showed poor memory, lowered psychomotor activity, and poor size estimation.

Temporal information processing by alcoholics

In time-discrimination tests using visual and auditory stimuli, more information was transmitted by social drinkers than by alcoholics, and cognitively unimpaired alcoholics transmitted more information than did cognitively impaired alcoholics.

The effects of scopolamine on the temporal control of behavior

Pigeons were provided access to food once every 75 sec independently of their behavior. The effects of scopolamine hydrobromide on the temporal distribution of locomotor activity during the interfood interval were evaluated on the basis of a recently developed model. Drug-induced changes in activity, as evaluated by the model, showed that scopolamine (a) decreased the effect of postfood inhibition, (b) decreased the effect of terminal behaviors that occur late in the interfood interval and compete or interfere with general activity, (c) decreased the total amount of activity engendered by the appetitive schedule of reinforcement, (d) and appeared to produce an underestimation of time intervals. These effects were systematically related to drug dosage.

The effects of d-amphetamine on temporal discrimination in the rat

The effects of d-amphetamine on temporal discrimination in the rat were studied. Rats were trained on a two-manipulandum task involving the discrimination between two tones differing only in duration. d-Amphetamine (0.1 - 1.6 mg/kg) disrupted performance on this task, although not in an obvious dose-related manner. Lever biases were enhanced by the drug, but inconsistenly among rats. Enhanced lever bias did not necessarily correlate with deterioration of performance. The drug lengthened both response latency and the performance of terminal components of the operant chain. However the characteristic pattern of response latencies produced by the two tones was not altered significantly by the drug. The results are discussed in terms of whether the drug disrupts discrimination performance by a direct effect on processes of temporal discrimination or indirectly, by its other effects on behavior.

A comparison of the effect of imipramine, nomifensine, and placebo on the psychomotor performance of normal males

Imipramine (50 mg), nomifensine (50 mg) or placebo was administered early morning, late morning, and mid-afternoon to normal volunteers. The program of hourly tests included: the Digit Symbol Substitution, Perceptual Reversal, Time Estimation Test, and Simple and Complex Continuous Performances tests both of which required recognition of briefly exposed letters of the alphabet. It was found that relative to placebo or nomifensine, imipramine had a clearly detracting effect on most of the tests. Drowsiness was reported more often in the imipramine group than in the placebo and nomifensine groups combined.

Differential association between chronic cannabis use and brain function deficits

To summarize, 12 objective tests that generated 16 test variables were administered to 850 male regular cannabis users and 839 nonusers. The tests were designed to assess various modalities, including speed of psychomotor performance, distance estimation, time estimation, immediate memory, and visuomotor coordination. Most of the test variables differentiated significantly between consumers and controls. At the same time, a significant second-order interaction emerged in most cases. This interaction meant that, under certain conditions that relate to the two dimensions "literacy-illiteracy" and/or "urbanism-ruralism," the superiority of controls over cannabis users became impressive, whereas under other conditions it almost disappeared. To account for this complex pattern of results, a working hypothesis was presented to the effect that "other conditions being equal, the lower the nondrug level of proficiency on tests of cognitive and psychomotor performance the smaller the size of function deficit associated with drug usage." For an empirical examination of the hypothesis, six predictions were formulated. Three predictions defined specific relationships between level of performance, on one hand, and each of three organismic variables, on the other: literacy, urbanism, and age. The remaining predictions delineated relationships to be expected between size of function deficit and the three organismic variables. All our predictions were confirmed, showing less function impairment to be contingent with cannabis usage among the illiterates, rurals, and older subjects. Level of cortical arousal was suggested as the central process associated with the three organismic variables. Because the version of our working hypothesis was formulated with reference to chronic material, the possibility of a transposition of the paradign to research on the acute effects of the drug was discussed. The suggestion was made that our working hypothesis, in either version, is capable of establishing genuine integration between reports that present conflicting results on possible function deficits contingent with cannabis consumption.