Although animals typically prefer to exert less effort rather than more effort to obtain food, the present research shows that requiring greater effort to obtain food at a particular location appears to increase the value of that location. In Experiment 1, pigeons' initial preference for one feeder was significantly reduced ...

RATIONALE: The CB1 receptor antagonist SR141716A reduces food intake in rats. This effect is likely to depend on modulation of reward related processes. OBJECTIVE: To investigate the effects of SR141716A on responding for food under a second order instrumental task in which responding and consumption of food can be separated, ...

Food-carrying behavior in foraging rats has been assumed to have an advantage to avoid risks by shortening time spent outside their nests. However, there is no experimental evidence for this. In the present study, food-carrying behavior for four sizes of food pellets (45, 100, 200, and 1000 mg) was measured ...

The effects of two anorectic drugs, dexfenfluramine and phentermine, on food intake under different food-access conditions were examined. Experiment 1 compared the effects of these drugs on food intake under a progressive-ratio (PR) schedule and free-access conditions. Dexfenfluramine decreased food intake under both conditions, but the doses required to decrease ...

A series of experiments was performed to determine whether sign-tracking would occur in rats with intravenous (i.v.) cocaine as the unconditioned stimulus. In Experiment 1, a retractable lever paired with food produced strong sign-tracking, but a lever paired with one of three doses of i.v. cocaine did not elicit any ...

Food-deprived rats that receive intermittent delivery of small amounts of food develop excessive drinking--specifically, schedule-induced polydipsia (SIP). A main characteristic of SIP is its occurrence at the beginning of interfood intervals. The purpose of this study was to demonstrate that SIP can be developed toward the end of interfood intervals, ...

Dopamine (DA) plays roles in circuits that are important for brain reward and in striatal brain regions that are important for certain types of habit learning. These processes in wildtype, heterozygous, and homozygous dopamine transporter knockout (DAT-KO) mice, which were mildly food deprived and allowed to make nose-poke responses for ...

RATIONALE: The dopaminergic pathways are involved in natural and drug reward related processes. OBJECTIVES: To compare the respective involvement of the dopaminergic receptors D1, D2 and D3 in natural-seeking versus drug-seeking behaviour and evaluate any concomitant expression of locomotor sensitisation. METHODS: In separate experiments, male Wistar rats were trained to ...

The effects of pharmacological manipulations on responding under extinction conditions were determined in baboons using a schedule of reinforcement that modeled food acquisition and food consumption. Responding during the initial acquisition component was reinforced by stimuli paired with food, while responding during the latter consumption component was reinforced with food. ...

Previous work indicated a role for GABA and glutamate in the reinforcing effects of drugs of abuse. The present studies assessed the effects of GABAergic and glutamatergic manipulations on the reinforcing effects of nicotine as assessed by intravenous nicotine self-administration. Male Wistar rats were allowed to self-administer either of two ...

Four pigeons and three ringneck doves responded on an operant simulation of natural foraging. After satisfying a schedule of reinforcement associated with search time, subjects could "accept" or "reject" another schedule of reinforcement associated with handling time. Two schedules of reinforcement were available, a variable interval, and a fixed interval ...

The serial order in which events occur can be a signal for different outcomes and therefore might be a determinant of how an animal should respond. In this report, we propose a novel design for studying serial order learning in Pavlovian conditioning. In both Experiments 1a and 1b, hungry rats ...

Recent experiments suggest that the effects of drugs of abuse on the discrimination of the passage of time may differ for experimenter-imposed and subject-produced events. The current experiment examined this suggestion by determining the effects of morphine on the discrimination of interresponse times (IRTs). Pigeons pecked a center key on ...

In a human fear conditioning paradigm using the skin conductance response (SCR), participants were assigned to two groups. Following identical acquisition, group ABA (n = 16) was extinguished to a generalization stimulus (GS), whereas group AAB (n = 20) was extinguished to the conditioned stimulus (CS). At test, presenting the ...

The extent of correlation and the latency of evoked potentials to sound, recorded bilaterally in the frontal cortex and lateral hypothalamus of cats, were studied at different stages of the acquisition of an operant food-related reflex and during sudden transfer to 30% food reinforcement. High correlation coefficients between the evoked ...

Myosin VI is a molecular motor that can walk processively on actin filaments with a 36-nm step size. The walking mechanism of myosin VI is controversial because it takes very large steps without an apparent lever arm of required length. Therefore, myosin VI is argued to be the first exception ...

BACKGROUND: Food reinforcement and dopaminergic activity may influence food consumption, but research on whether they interact has not been performed. OBJECTIVE: We assessed the effects of food reinforcement and the interaction of food reinforcement with the dopamine transporter (SLC6A3) genotype and the dopamine D(2) receptor (DRD(2)) genotype on energy consumption. ...

In 4 experiments rats received appetitive Pavlovian conditioning followed by extinction. Food accompanied every trial with the conditioned stimulus (CS) for the continuously reinforced groups and only half of the trials for the partially reinforced groups. In contrast to previous experiments that have compared the effects of partial and continuous ...

In Experiment 1, pigeons responded on concurrent-chains schedules with equal variable-interval schedules as initial links and fixed delays to food as terminal links. One terminal-link delay was always three times as long as the other. As terminal-link delays increased, response percentages on the key with the shorter terminal link increased ...

The integration of spatial maps in pigeons was investigated using a spatial analog to sensory preconditioning. The pigeons were tested in an open-field arena in which they had to locate hidden food among a 4x4 grid of gravel-filled cups. In phase 1, the pigeons were exposed to a consistent spatial ...

Developments in the genetic manipulation of mice have intensified interest in the relation between genes, environment and learned behavior, which in turn has led to exploration of experimental procedures for assessing genetic influences on learning using methods such as response acquisition. The requirement for multiple experimental control groups in such ...

Resistance to change has been studied in several species such as humans, rats, and pigeons. We conducted two experiments using goldfish as subjects to examine the generality of the findings on resistance to change in a phylogenetically more primitive species. In Experiment 1, five goldfish (Carassius auratus) were trained on ...

Relatively little is known about the role of the inhibitory neurotransmitter gamma-aminobutyric acid (GABA) in extinction of appetitively motivated tasks. The benzodiazepine (BZ) chlordiazepoxide (CDP) was administered during extinction and re-acquisition of lever pressing by mice following food reinforced discrete-trial fixed-ratio 5 (FR-5) training. Typical FR behaviour was established during ...

Both the hedonic ratings and the reinforcing value of food have been considered to be determinants of food intake. The objective of this study was to compare the pleasurable ratings and the reinforcing value of food as determinants of energy intake. Seventy-four smokers were studied in food consumption and reinforcing ...

Pigeons' keypecking was reinforced by food on baseline schedules of multiple variable interval (VI) x VI x and on contrast schedules of multiple VI x VI y. Deprivation of food was varied by maintaining subjects at 75%, 85%, and 95% (+/- 2%) of their free-feeding weights. Positive and negative behavioral ...

Rats' operant responding for sucrose rewards in the 1st half of a session can vary directly with the conditions of reward in the 2nd half. The authors investigated whether that induction effect represented an animal model of emotive states. Rats pressed a lever for either ethanol or sucrose rewards in ...

Cocaine addiction has been characterized by a shift from controlled to uncontrolled and compulsive drug use. Using novel self-administration procedures, we attempted to model this transitional phase and characterize the behavioral changes that underlie it. We chose to use food-reinforced responding across the light/dark cycle as an indicator of the ...

Key pressing of rats was maintained under multiple and discrete-trial choice schedules with reinforcer units of 45 mg food pellets or 3.5 s dips of sucrose solution. Both smaller and larger fixed ratio (FR) schedules were associated with the same unit price in a manner, for example, that each of ...

We have compared the effect of two distinct Ih inhibitors on the temporal properties of the ERG response that, as previously shown, correlates well with the HCN activation in rods. The present results confirm the notion that cilobradine is more effective than zatebradine in inducing bradycardia. Importantly, the doses of ...

The purpose of this study was to determine how stimuli paired with food alters the effects of pharmacological and dietary manipulations on food intake. Responding of baboons was studied using a schedule of reinforcement that simulated food 'seeking' and food 'taking'. Under one condition, responding during the initial seeking component ...

Rats obtained food pellets on a variable-interval schedule of reinforcement by nose poking a lighted key. After training to establish baseline performance (with the mean variable interval set at either 60, 120, or 240 s), the rats were given free access to food during the hour just before their daily ...

As body weight increases, the excitatory strength of a stimulus signaling an opportunity to run should weaken to a greater degree than that of a stimulus signaling an opportunity to eat. To test this hypothesis, six male albino Wistar rats were placed in running wheels and exposed to a fixed ...

Experiments on Sprague-Dawley rats using vital intracerebral dialysis and HPLC with electrochemical detection demonstrated that presentation of the animals with inedible imitation food or food containing a bitter flavor instead of the expected food reinforcement led to rapid increases in glutamate levels in the intercellular space of the nucleus accumbens. ...

Pigeons accustomed to food reinforcement for responding in the presence of a 25-Hz flickering light were exposed to several sets of flicker-frequency stimuli arranged as increasing and decreasing series. In the first experiment, food was occasionally delivered for key pecks during 30-s periods of 25-Hz flicker appearing at the beginning, ...

RATIONALE: Hypoglycemia leads to undernutrition of the brain. Favoring selective processing of food stimuli would be an adaptive cognitive strategy. However, hypoglycemia is known to impair several aspects of cognitive function, and it is unknown whether selective cognitive processing of food stimuli occurs during insulin-induced hypoglycemia. METHODS: In a single-blind ...

SUMMARY Drugs of abuse becomes increasingly present in today’s affluent society. Immoderate drug abuse has risen to a deadly serious problem in today’s youth. Animal research with operant conditioning approach is one way of fathoming this problem and can contribute to gaining a clearer understanding of drug addiction. In order ...

In the current investigation, we evaluated the relative effects of noncontingent reinforcement (NCR), escape extinction, and a combination of NCR and escape extinction as treatment for the feeding problems exhibited by 4 children. For each participant, consumption increased only when escape extinction was implemented, independent of whether NCR was present ...

Pigeons were exposed to multiple and concurrent second-order schedules of token reinforcement, with stimulus lights serving as token reinforcers. Tokens were produced and exchanged for food according to various fixed-ratio schedules, yielding equal and unequal unit prices (responses per unit food delivery). On one schedule (termed the standard schedule), the ...

In the present experiment, the authors investigated the idea that within-session changes in operant response rates occur because subjects sensitize and then habituate to the reinforcer. If that is true, then altering an aspect of the reinforcer within the session should alter the observed within-session responding. The authors tested that ...

The nucleus accumbens is a brain region that participates in the control of behaviors related to natural reinforcers, such as ingestion, sexual behavior, incentive and instrumental learning, and that also plays a role in addictive processes. This paper comprises a review of work from our laboratory that focuses on two ...

In the time-left experiment (J. Gibbon & R. M. Church, 1981), animals are said to compare an expectation of a fixed delay to food, for one choice, with a decreasing delay expectation for the other, mentally representing both upcoming time to food and the difference between current time and upcoming ...

Synthetic hydroxyapatite (HA) whiskers have been utilized as a new, biocompatible reinforcement for orthopedic biomaterials. High-density polyethylene (HDPE) was reinforced with either the synthesized HA whiskers or a commercially available spherical HA powder using a novel powder processing technique that facilitated uniform dispersion of the reinforcements in the matrix prior ...

Repeated presentation of food cues results in habituation in adults, as demonstrated by a decrement in salivary responding that is reversed by presenting a new food cue in adults. Food reinforced behavior in animals shows the same pattern of responding, with a decrease in responding to obtain the food, followed ...

Observing responses produce contact with discriminative stimuli and have been considered analogous to attending. Many studies have examined the effects of reinforcement rate on the resistance to change of simple operant behavior, but nothing is known about the resistance to change of observing. Two experiments examined the effects of primary ...

Pigeons were trained on multiple schedules that provided concurrent reinforcement in each of two components. In Experiment 1, one component consisted of a variable-interval (VI) 40-s schedule presented with a VI 20-s schedule, and the other a VI 40-s schedule presented with a VI 80-s schedule. After extended training, probe ...

Pigeons responded on a concurrent-chains schedule with two equal variable-interval (VI) schedules as initial links and delays to food of 3 and 12s as the two terminal links. In even-numbered sessions, no other reinforcement schedule was present, and all pigeons showed a strong preference for the response key that had ...

RATIONALE: Effects of compounds on punished responding have been predictive of anxiolytic efficacy in humans. The use of mice in these tests has been limited, but the utility of this species in drug discovery and for neurobiological inquiry would benefit from a rapid, reliable method. OBJECTIVES: The present experiments were ...

RATIONALE: The effects of drugs on performance of tasks used to assess attention might be confounded with changes in motivation. Few studies have investigated the role of motivational factors in such situations. OBJECTIVES: To determine how changes in motivation for food influence performance of the 5-choice serial reaction time task ...

The effects of rapid-eye movement sleep deprivation (REMSD) in rats were studied in relation to variable-interval (VI) reinforcement schedule value. Initially, lever pressing was maintained on a VI 30-s schedule of food pellet delivery. After a baseline was established, rats were repeatedly exposed to 96 hr of REMSD and control ...

We report two experiments using a concurrent-chains procedure in which one terminal-link schedule was fixed-interval 8 s and the alternative schedule changed randomly from day to day. In Experiment 1, the alternative schedule varied between 4 s and 16 s according to a pseudorandom binary sequence similar to the one ...