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PubMed1974

Relative and absolute density of reinforcement as factors influencing the peak shift.

Four groups of six pigeons each were given nondifferential training on multiple variable-interval variable-interval reinforcement schedules and then were switched to differential training involving a multiple schedule in which reinforcement density was reduced in one of the two components. The multiple schedules used in the four groups had mean interreinforcement intervals of 1 min and 1 min in the two components changed to 1 min, 5 min; 2.5 min, 2.5 min changed to 2.5 min, 5 min; 12 sec, 12 sec changed to 12 sec, 24 sec; and 12 sec, 12 sec changed to 12 sec, 60 sec. In subsequently administered wavelength generalization tests, some peak shifts were observed in each condition and occurred occasionally in the absence of behavioral contrast or rate reduction in the less-reinforced component. The best predictor of peak shift was a high proportion of total responses emitted during the more-reinforced component at the end of differential training.

Journal Article↗
PubMed2002

The selective glycine antagonist gavestinel lacks phencyclidine-like behavioral effects.

Gavestinel [GV150526A; ( E)-3[(phenylcarbamoil)ethenyl]-4,6-dichloroindole-2-carboxylic acid sodium salt] is a selective antagonist at the strychnine-insensitive glycine site of the -methyl-D-aspartate (NMDA) receptor. It was tested for its ability to substitute for phencyclidine (PCP) in rats and rhesus monkeys trained to discriminate PCP from saline, under a two-lever fixed-ratio (FR) food reinforcement schedule, and for its ability to maintain responding in rhesus monkeys trained to self-administer PCP under a FR reinforcement schedule. No PCP-lever responding was observed after gavestinel (1-56 mg/kg i.p.) administration to rats discriminating PCP (2.0 mg/kg i.p.) from saline. The highest dose of gavestinel (100 mg/kg i.p.) tested eliminated responding. Likewise, no PCP-lever responding was observed after gavestinel (1-30 mg/kg s.c.) administration to rhesus monkeys discriminating PCP (0.08 or 0.1 mg/kg i.m.) from saline; the highest dose of gavestinel (30 mg/kg s.c.) tested reduced response rates to approximately 50% of those observed after its vehicle ( -cyclodextrin in 0.9% saline). Gavestinel (0.1-1 mg/kg per i.v. infusion) was not self-administered by rhesus monkeys that reliably self-administered PCP (0.0056 or 0.01 mg/kg per i.v. infusion). Infusion rates at the highest dose were typically lower than those for vehicle or saline, suggesting behavioral activity. Together, these results suggest that at behaviorally active doses gavestinel is not PCP-like and is likely to have low abuse liability.

Animals↗
PubMed1971

Signaled reinforcing brain stimulation facilitates operant behavior under schedules of intermittent reinforcement.

When single, rewarding brain stimulations were mnade predictable by preceding them with a brief warning signal, operant behavior was established and maintained under fixed ratio 200, variable ratio 30, fixed interval 3-minute, variable interval 2-minute, and differential reinforcement of low rate 20-second schedules of intermittent reinforcement. When the warning signal was removed, overall response rate declined in all but the fixed ratio schedules and then returned to the previous rate when the signal was reinstated.

Animals↗
PubMed1974

The relationship between observing behavior and food-key response rates under mixed and multiple schedules of reinforcement.

Pigeons were trained under an observing response procedure in which pecks on one key (food key) were reinforced under a mixed fixed-interval 30-sec extinction schedule. A response on a second (observing) key replaced the mixed-schedule stimulus with either of two multiple-schedule stimuli (red and green keylights) for 5 sec. Observing response rates were positively correlated with food-key response rates in the presence of multiple-schedule stimuli and inversely related to food-key response rates in the presence of mixed-schedule stimuli. These results suggest that observing response output is controlled not only by the stimuli produced by observing responses but also by the stimuli in the presence of which observing responses occur. The possibility that observing responses alter the probability of reinforcement is advanced.

Journal Article↗
PubMed1983

Nicotine self-administration in baboons.

Two experiments were conducted in which responding maintained by nicotine and cocaine was studied under two different schedules of drug delivery. In Experiment 1, nicotine (0.01-0.32 mg/kg IV) was available under a fixed-ratio 2 timeout 15 sec reinforcement schedule. When nicotine was substituted for cocaine or saline, dose-dependent differences in self-administration were evident across the first five sessions, resulting in an inverted U-shaped dose-effect curve. With continued exposure to each nicotine dose, however, number of injections generally stabilized at levels not very different, if at all, from saline; and the terminal dose-effect functions generally were low and flat. In Experiment 2, nicotine (0.01-0.56 mg/kg IV) was available under a fixed-interval 5 min timeout 60 sec reinforcement schedule. Response rates were considerably lower and response patterning was less likely to be scalloped than when responding was maintained by either cocaine or food, but number of injections was higher than those maintained by saline. When fixed-interval value was varied, number of nicotine reinforcements remained low and virtually constant, but number of food reinforcements increased as the fixed interval decreased. The present results, along with those from previous studies, suggest that the ability of nicotine to serve as a reinforcer appears to be strongly influenced by the conditions of drug availability, perhaps more so than for other drugs of abuse.

Animals↗
PubMed1983

Steady-state performance on fixed-, mixed-, and random-ratio schedules.

Three groups of rats pressed a lever for milk reinforcers on various simple reinforcement schedules (one schedule per condition). In Group M, each pair of conditions included a mixed-ratio schedule and a fixed-ratio schedule with equal average response:reinforcer ratios. On mixed-ratio schedules, reinforcement occurred with equal probability after a small or a large response requirement was met. In Group R, fixed-ratio and random-ratio schedules were compared in each pair of conditions. For all subjects in these two groups, the frequency distributions of interresponse times of less than one second were very similar on all ratio schedules, exhibiting a peak at about .2 seconds. For comparison, subjects in Group V responded on variable-interval schedules, and few interresponse times as short as .2 seconds were recorded. The results suggest that the rate of continuous responding is the same on all ratio schedules, and what varies among ratio schedules is the frequency, location, and duration of pauses. Preratio pauses were longer on fixed-ratio schedules than on mixed-ratio or random-ratio schedules, but there was more within-ratio pausing on mixed-ratio and random-ratio schedules. Across a single trial, the probability of an interruption in responding decreased on fixed-ratio schedules, was roughly constant on random-ratio schedules, and often increased and then decreased on mixed-ratio schedules. These response patterns provided partial support for Mazur's (1982) theory that the probability of instrumental responding is directly related to the probability of reinforcement and the proximity of reinforcement.

Journal Article↗
PubMed1978

Studies on responding under fixed-interval schedules of reinforcement: II. The scalloped pattern of the cumulative record.

Responding under fixed-interval schedules usually generates either scalloped or break-and-run cumulative records. Earlier, it was generally accepted that the characteristic pattern was the scallop, but in recent years there has been an increasing emphasis on the break-and-run pattern. The break-and-run pattern has been shown quantitatively to provide a good fit of certain fixed-interval patterns. In the present work, responding during fixed-interval 1000-second components of a multiple fixed-interval 1000-second fixed-ratio 50 responses schedule was examined in two rhesus monkeys. Even after responding had started in an interval, there was a high tendency for responding to accelerate over subsequent 100-second segments of the interval. In segments with responding, the rate increased from one segment to the next in 303 of 389 segments in one monkey and in 310 of 419 segments in the other. The size of the increase was substantial, the rate in the fifth segment after responding started being an average of 4.5 times higher than the rate in the first segment after responding started. Hence, the usual pattern of responding in individual intervals was of sustained and substantial acceleration, vindicating numerically the conclusion derived from inspection of the scalloped patterns of the cumulative records.

Journal Article↗
PubMed2001

Schedule control of quantal and graded dose-effect curves in a drug-drug-saline discrimination.

Pigeons were trained to discriminate among 5 mg/kg pentobarbital, 5 mg/kg morphine, and saline when responding was maintained under fixed-interval (FI) or fixed-ratio (FR) reinforcement schedules. After the discrimination was established, other drugs were substituted for the training drugs. After low doses of pentobarbital and chlordiazepoxide, responding shifted from the saline key to the pentobarbital key under both FR and FI schedules. After low doses of morphine and methadone, responding shifted from the saline key to the morphine key under both reinforcement schedules. After all doses of d-amphetamine, responding occurred largely on the saline key under both schedules. Responding also was confined largely to the saline key after phencyclidine administration under the FR schedule, but under the FI schedule, responding shifted from the saline key to the pentobarbital key at high doses of phencyclidine. When responding was maintained under the FR schedule, the dose-response curves for drugs that generalized to the training drugs were quantal in shape, while under the FI schedule, the dose-response curves for drugs that generalized to the training drugs were graded. These data extend observations that FR schedules generate quantal dose-response curves, and FI schedules generate graded dose-response curves to complex three-key drug discriminations.

Animals↗
PubMed1967

Conditioning of the aggressive behavior of pigeons by a fixed-interval schedule of reinforcement.

Operant reinforcement of aggression was studied in food-deprived pigeons by delivering food for attacks against a target pigeon. The food was delivered according to a fixed-interval schedule and attack behavior was recorded automatically. Attack could be conditioned and extinguished, and the proportion of time spent in attack was a direct function of the frequency of reinforcement of the attack. The fixed-interval schedule produced an increasing rate of attack during the interval between food reinforcements. This positive curvature was an inverse function of the duration of the interval. The findings revealed that the duration and temporal patterning of the complex social behavior of attack can be influenced in a substantial and predictable manner by the schedule and frequency of operant reinforcement.

Aggression↗
PubMed2004

Effect of behavioral history on subsequent responding: experiments using rotary fixed-ratio schedules.

The present study proposes a novel experimental approach to examine the effect of previous schedule history on subsequent responses. College students used a three-button device to indicate their choice of response. We performed two experiments. Each experiment consisted of three phases. In experiment I, fixed-ratio 10 (FR 10) reinforcement schedule was employed in phases 1 and 3. Phase 2 employed "Rotary-FR 10" schedule: after obtaining a point produced by pressing one of three specified buttons in a triangular array 10 times, the effective button changed to another in a clockwise direction. Optimal response pattern for Rotary-FR 10 was analyzed. Two types of behavior, referred to as "consecutive" and "scatter" were observed in phase 1. The mean number of optimal responses in consecutive type was significantly higher than scatter type in phases 2 and 3. In experiment II, two schedules were used in phase 1, and the same protocol used in experiment I was followed. We found that the reinforcement schedule used in phase 1 affected acquisition of the optimal response in phase 2. These results suggest that the earlier behavioral tendencies play an important role in determining subsequent behavior and that such behavioral tendency can be modified by specifically designed protocols.

Choice Behavior↗
PubMed1998

The effects of dopamine D3/D2 receptor agonists on intracranial self stimulation in the rat.

The effects of the dopamine D3/D2 receptor agonists quinpirole, quinelorane and (+/-)7-OH-DPAT [(+/-) 7-hydroxy-2(N,N-di-n-propylamino) tetralin] on intracranial self-stimulation (ICSS) were investigated. Rats implanted with bipolar electrodes into the lateral hypothalamus were trained to lever press on a continuous reinforcement schedule for positively reinforcing trains of electrical stimulation. Three measures of responding were calculated; the frequency at which responding was 50% of the maximum (M50), the asymptotic response rate and the total area under the curve (AUC) for each frequency sweep. Quinpirole (2.2-66.0 microg/kg SC) significantly increased M50 and reduced both asymptote and AUC. Quinelorane (0.25-79.0 microg/kg SC) had no significant effect on M50 values but significantly reduced both asymptote and AUC. (+/-)7-OH-DPAT (2.5-74.0 microg/kg) did not significantly affect any of the measures. The data show that low doses of quinpirole and quinelorane, but not (+/-)7-OH-DPAT, inhibit ICSS maintained by electrodes in the lateral hypothalamus. Either dopamine D2 or dopamine D3 receptor stimulation may play a role in mediating ICSS inhibition, but studies with more selective receptor agonists and antagonists are required to define the role of each receptor.

Animals↗
PubMed1998

Lesions of the hippocampus or fornix do not interfere with the relative validity effect on a discrete stimulus or the context.

Two experiments with rats used an appetitively motivated instrumental discrimination procedure to examine whether damage to the hippocampal system would interfere with the relative validity effect in which a partially reinforced stimulus trained in compound acquires a weak conditioned response when concurrently trained CSs are perfect predictors of the presence or absence of the US [A.R. Wagner, F.A. Logan, K. Haberlandt, T. Price, Stimulus selection in animal discrimination learning, J. Exp. Psychol. 76 (1968) 171-180]. The true discrimination (TD) group received training with two compound cues containing a common element. One compound was reinforced and another never reinforced (AX+, BX-). Following TD training the common element (X) failed to acquire a strong conditioned response in comparison to a control, pseudo discrimination (PD) group (AX+/-, BX+/-), in which both compound cues were reinforced 50% of the time. Although (X) was reinforced on a partial reinforcement schedule, (50%) in both groups, conditioning of X was affected by the reinforcement schedules of the accompanying elements (A and B). Neither radio-frequency lesions of the fornix-fimbria (Experiment 1) nor neurotoxic lesions of the hippocampus (Experiment 2) interfered with this effect on X or on the same effect found during the inter trial interval (ITI). Rates of ITI responding were higher in the PD groups than in the TD groups suggesting stronger contextual conditioning following PD training. Furthermore, disruptions to the hippocampal system in Experiment 2 resulted in increased rates of lever pressing for food. These results do not support the notion that the hippocampus is critically involved in selective associations.

Animals↗
PubMed1972

Punishment contras during free-operant avoidance.

Punishment of bar-pressing responses of rhesus monkeys with electric shock in one component of a multiple free-operant avoidance schedule suppressed responding in that component. These decreases were concomitant with response rate increases in the unpunished component (punishment contrast). Response rates in both components increased when punishment was removed and decreased in successive sessions. These effects of punishment on unpunished responding were similar to those obtained during single and multiple schedules of positive reinforcement and they suggest a further similarity in the development of discriminations during positive and negative reinforcement schedules.

Journal Article↗
PubMed1974

The role of elicited responding in behavioral contrast.

An attempt was made to separate operant and elicited pecks occurring in multiple schedules of food reinforcement by moving the component stimuli to a second key, upon which pecks had no effect. The operant key stimulus was constant, regardless of the reinforcement schedule in effect. Experiments included two- and three-component multiple schedules and a comparison of the single-key and the two-key procedures. In general, conditions that typically produce positive contrast in single-key procedures reduced responding to the constant-stimulus key (induction) and increased responding to the component-stimulus key (contrast) in the two-key procedure. The results were interpreted as supporting the contention that two response classes, operant and elicited, are present in standard multiple schedules. In addition, elicited responses were strongly implicated in contrast phenomena.

Journal Article↗
PubMed1987

Stimulus control and the development of behavioral tolerance to daily injections of d-amphetamine in the rat.

We examined whether daily d-amphetamine administration affected behavior under the control of external stimuli differently than behavior not under such control. Two variants of a fixed-consecutive-number reinforcement schedule were combined in a multiple schedule. An external discriminative stimulus indicated when the schedule requirement for reinforcement had been satisfied in one component, no such stimulus was used in the other component. Reinforcement frequency was roughly equated between the components by reducing the probability of reinforcement in the added stimulus component. Two groups of animals were given daily i.p. injections with equivalent doses of drug. Tolerance to the drug's behavioral effects developed when injections occurred before behavioral evaluation but did so only to a limited extent when injections were given only after the sessions. This indicated that behaving in the presence of the drug facilitated the development of such tolerance. It developed under both stimulus control conditions at both doses; at 3.0 mg/kg, it developed predominantly in those aspects of behavior that were under the control of external discriminative stimuli. Although drug-related decreases in reinforcement frequency in some animals were correlated with behavioral tolerance development, differential tolerance development was not associated consistently with such reductions. Establishing discriminative control of behavior by external stimuli can both reduce sensitivity to repeated d-amphetamine administration and facilitate the development of tolerance to its behavioral effects.

Animals↗