Fixed-interval Schedule Of Food Presentation Research Articles

Effects of chlordiazepoxide on comparable rates of punished and unpunished responding.

Identical overall rates and patterns of key pecking by pigeons were maintained under a multiple fixed-interval schedule of food presentation. In one component, every thirtieth response produced an electric shock (punishment) whereas during the other component the response that produced food had to be preceded by a pause of a minimum (10 or 11 s) duration. Although chlordiazepoxide (1.0--17.0 mg/kg) increased both punished and unpunished responding, greater increases were uniformly obtained with punished responding.

Attenuating the rate-decreasing effects of phenylpiperidine analgesics by pentobarbital.

The ability of pentobarbital, diazepam, and chlorpromazine to attenuate the rate-decreasing effects of a high dose (10 or 30 mg/kg) of meperidine was tested in pigeons responding under a multiple fixed-ratio, fixed-interval schedule of food presentation. Pentobarbital (10 mg/kg) attenuated the meperidine-induced rate decreases, whereas diazepam (0.3--3 mg/kg) or chlorpromazine (3--30 mg/kg) did not reliably attenuate the response rate decreases. The combination of 10 mg/kg of pentobarbital and meperidine resulted in a marked disruption of the pattern of responding in the fixed-interval component of the multiple schedule. Pentobarbital (1, 3, 10, and 17.5 mg/kg) was also tested in combination with rate-decreasing doses of normeperidine (17.5 mg/kg), anileridine (10 mg/kg), alphaprodine (10 mg/kg), and fentanyl (0.3 mg/kg). Pentobarbital reliably attenuated the rate-decreasing effects of normeperidine, anileridine, and alphaprodine, but not the rate decreases induced by fentanyl.

Food, water and ethanol consumption by rats under a fixed-interval schedule of food presentation

Rats could lever press 24 hours a day for 97 mg food pellets under a fixed-interval (FI) 90 second schedule. During the first 4 days, an ethanol solution was the only available fluid, after which both water and ethanol solutions were available. At ethanol concentrations (w/v) of 5%, 7.5% and 10%, total caloric intake and total fluid intake remained constant, while ethanol consumption was inversely proportional to the concentration of the solution. When the FI 90 s schedule was changed to FI 45 s, or to FI 180 s, there were only small changes in total caloric intake, total fluid intake and in percentages of total fluid consumptipn and total caloric intake as ethanol. The data suggest that the intake of ethanol under this fixed-interval schedule depends more on the ethanol concentration than on the calories obtained from ethanol drinking.

Effects of d-amphetamine, chlordiazepoxide and promazine on responding of squirrel monkeys maintained under fixed-interval schedules of food presentation and stimulus-shock termination

Responding of two squirrel monkeys was maintained under a multiple 5-min fixed-interval schedule of food presentation and termination of a stimulus in the presence of which shocks occurred. Under the stimulus-shock termination schedule, shocks occurred independently of responding, on the average of every three minutes; a response after 5 min terminated the prevailing stimulus and shock-presentation schedule. Response rates and patterns of responding under both schedules were comparable although they differed slightly between monkeys. d-Amphetamine increased and promazine decreased responding under both fixed-interval schedules. Chlordiazepoxide increased responding maintained by food presentation but decreased responding maintained by termination of the stimulus-shock complex. Under certain conditions and with certain drugs, the event that maintains responding can determine the effects a drug will have on behavior.

Chronic mercuric chloride: Behavioral effects in pigeons

The effects of daily doses (1, 3, 10 mg/kg, im) of mercuric chloride were studied in pigeons responding under multiple fixed-ratio, fixed-interval schedules of food presentation. The effects also were studied in pigeons responding under a multiple fixed-ratio schedule which had several intensities of a visual stimulus controlling the performance and under a repeated acquisition schedule which required the pigeon to learn a different four-step, three-position sequence every test day. Across all test conditions, the daily doses of 1 mg/kg produced some increases in the variability of the rates of responding, but no consistent decreases. Daily doses of 3 and 10 mg/kg reliably decreased responding, and these decreases disappeared gradually after daily dosing was discontinued. Daily 10 mg/kg doses in three birds which were not being tested killed two birds after 17 and 28 injections, but the third bird survived 60 injections.

Reinforcement and Punishment of Behavior by the Same Consequent Event

In daily sessions, lever-pressing by each of two squirrel monkeys was maintained under two different conditions. During one condition responding that had been maintained initially under a 5-min. fixed-interval schedule of food presentation was suppressed when every 30th response produced an electric shock. In the presence of a different discriminative stimulus responding that initially postponed electric shock (avoidance) was ultimately maintained when responding instead produced shock under a 5-min. fixed-interval schedule. Thus responding was suppressed by shock presentation during one condition (punishment) and was maintained by the presentation of an identical shock during a second condition (reinforcement). Whether an environmental stimulus exerts reinforcing or punishing effects on behavior can depend on characteristics other than the nature of the event.

Behavioral interactions between naloxone and dopamine agonists

A fixed-interval schedule of food presentation was used to study the effects of apomorphine, ET-495 and clonidine and interactions between these drugs and naloxone in the rat. The rate of responding under this schedule was decreased by low doses of apomorphine (0.03–0.3 mg/kg), ET-495 (0.3–1.0 mg/kg) and clonidine (0.03–0.3 mg/kg). Naloxone, at a dose (3 mg/kg) which did not itself alter responding, potentiated the rate decreasing effects of apomorphine and ET-495 but did not alter the effects of clonidine. It is suggested that the rate decreasing effects of low doses of apomorphine and ET-495 may be related to presynaptic inhibition of dopamine neurons and that under certain circumstances naloxone may also inhibit dopaminergic activity.

Changes in the rate-increasing effects of d-amphetamine and pentobarbital by response consequences

Keypecking in one group of pigeons was maintained under schedules in which food was presented only when a specified number of responses was followed by a 30-s pause without a response. d-Amphetamine and pentobarbital increased low rates of responding (and, thus, decreased food presentation) only after initial injections or when, during drug sessions, responses during the 30-s period did not reset the period. When responses during the pause-interval postponed food delivery, the rate-increasing effects of both drugs diminished over succeeding administrations. Thus, immediate effects of response consequences were as influential as the actual presence of a drug in determining the reproducibility of the behavioral effects of that drug. In a second experiment, keypecking in another group of pigeons was maintained under a 10-min fixed-interval schedule of food presentation but suppressed by a 100-response fixed-ratio schedule of shock delivery (punishment). d-Amphetamine and pentobarbital increased low rates of punished responding when shock delivery was eliminated during drug sessions. Pentobarbital, but not d-amphetamine, also increased punished responding when shock delivery was present. Rate-increasing effects of these drugs were determined by not only predrug patterns of responding but also effects of reinforcers and punishers that occurred during exposure to the drug.

AN ANALYSIS OF RATS' DRINKING‐TUBE CONTACTS UNDER TANDEM AND FIXED‐INTERVAL SCHEDULES OF FOOD PRESENTATION1

Rats' lever presses and drinking-tube contacts were studied under fixed-interval schedules of food presentation and under a tandem schedule composed of three fixed intervals. One group of rats was exposed first to the tandem schedule, next to fixed-interval schedules of comparable interpellet intervals, and once again to the tandem schedule; a second group of rats was exposed first to a fixed-interval and then to the tandem schedule. Under the tandem schedule, lever presses occurred at a higher rate and were more uniformly distributed in time than under the fixed-interval schedule. Tube contacts emitted by rats exposed first to a fixed-interval schedule consisted mostly of tongue contacts, which occurred at a high rate shortly after food; tube contacts emitted by rats exposed first to the tandem schedule consisted mostly of paw contacts, which occurred at a lower rate at times other than shortly after food. Changing the schedule from fixed interval to tandem decreased the frequency of tongue contacts for all rats. Under schedules of food presentation with comparable interpellet intervals, the schedule of food presentation, rather than the rate of food delivery per se, determined the topography and temporal locus of drinking-tube contacts.

Effects of chlorpromazine and d-amphetamine on observing responses during a fixed-interval schedule.

Pigeons were trained to peck a response key that briefly produced stimuli correlated with the passage of time in a fixed-interval schedule of food presentation for pecks on another response key. Pecks on the key that produced food were not likely near the end of each fixed interval, whereas pecks on the key that produced the discriminative stimuli were most likely to occur during the middle portion of each fixed interval. Chloropromazine (3.0--30.0 mg/kg) and d-amphetamine (0.03--3.0 mg/kg) produced inverted U-shaped dose-effect curves with response rate on the food-producing key as the dependent variable, and monotonically decreasing functions were obtained for the discriminative-stimulus producing responses. A "rate-dependency" interpretation adequately described the drug effects on the temporal distributions of pecks on the food-producing key, but was not consistent with the disruption of the temporal distribution of pecks on the key that produced the discriminative stimuli. The pecks on the discriminative-stimulus producing key had some of the properties of schedule-induced, or adjunctive, behavior. The effects of amphetamine and chlorpromazine on the rate of adjunctive behaviors may not be predictable from control rates.

Punished behavior: increases in responding after d-amphetamine.

Responding maintained in squirrel monkeys under a 10-min fixed-interval schedule of food presentation was suppressed by presenting a shock after every 30th response (punishment). During alternate 10-min periods of the same experimental session, but in the presence of a different discriminative stimulus, responding either had no effect (extinction) or postponed delivery of an electric shock (avoidance). During sessions when the avoidance schedule was not in effect, d-amphetamine sulfate decreased punished responding. When the avoidance schedule was present during alternate 10-min periods, however, d-amphetamine (0.01 minus 0.56 mg/kg, i.m.) markedly increased responding during punishment components. Increases in responding during avoidance components were also evident. The effects of d-amphetamine on punished responding depend on the context in which that responding occurs.

Effects of chlordiazepoxide on schedule-induced water and alcohol consumption in the squirrel monkey.

Lever pressing of five squirrel monkeys was maintained by a 3-min fixed-interval schedule of food presentation. 3 monkeys had water concurrently available and, for a second pair of monkeys, initially water, then increasing concentrations of alcohol (1--3% v/v) were present. Substantial amounts of post-pellet drinking occurred with all five monkeys. The amount of water ingested was approximately 100 ml per session, that of 3% alcohol nearly 63 ml. For the monkeys drinking alcohol, increasing concentrations of alcohol decreased both the rate of lever pressing and the volume of fluid consumed. Chlordiazepoxide (1.0--17.0 mg/kg) produced increases in lever pressing and in the schedule-induced consumption of both 3% alcohol and water.

SCHEDULES OF RESPONSE‐INDEPENDENT CONDITIONED REINFORCEMENT1

Rates and patterns of responding of pigeons under response-independent and response-dependent schedules of brief-stimulus presentation were compared by superimposing 3-min brief-stimulus schedules on a 15-min fixed-interval schedule of food presentation. The brief-stimulus schedules were fixed time, fixed interval, variable time, and variable interval. When the brief stimulus was paired with food presentation, its effects depended upon the schedule and ongoing rates. Fixed- and variable-interval brief-stimulus schedules enhanced the low rates normally occurring early in the 15-min interval, whereas fixed- and variable-time schedules suppressed these rates. Although the overall rates later in the interval were not affected to any great extent, the fixed brief-stimulus schedules generated patterns of positively accelerated responding between stimulus presentations. These patterns appeared less frequently under the variable brief-stimulus schedules. Initially, when not paired with food delivery, presentations of the brief stimulus produced relatively little effect on either response rate or patterning. However, once the stimulus had accompanied food presentation, the original performance under the nonpaired condition was not recovered. The effects were more like those occurring when the stimulus was paired with food.

Interactions between Naloxone and Chlorpromazine on behavior under schedule control.

A multiple fixed-ratio, fixed-interval schedule of food presentation was used to study interactions between naloxone and chlorpromazine in the pigeon. Inactive doses of both drugs could combine to decrease the rate of responding under both schedule components. Inactive doses of naloxone could enhance the rate-decreasing effects of chlorpromazine and inactive doses of chlorpromazine could enhance the rate-decreasing effects of naloxone. When both drugs decreased the rate, the combined effects of the drugs was greater than the sum of the rate-decreasing effects of the individual drugs. These data suggest that the rate-decreasing effects of naloxone and chlorpromazine are synergistic.

Development of behavioral tolerance to morphine and methadone using the schedule-controlled behavior of the pigeon.

A multiple fixed-ratio, fixed-interval schedule of food presentation was used to study the development of behavioral tolerance to daily injections of equipotent doses of morphine and methadone in the pigeon. There was evidence that tolerance was developing to the rate-decreasing effects of both drugs after a single injection. Tolerance to morphine developed more rapidly during the first week of injections than did tolerance to methadone. Tolerance to the depressant effects of morphine and methadone was less complete under the fixed-ratio component of the schedule than under the fixed-interval component. After repeated injections, increases in the rate of responding were observed in some birds. These increases depended on the bird, rather than on the narcotic. Thus, the development of tolerance was a function of the drug, of the individual bird, and of the schedule maintaining the behavior.

Rate-dependent effects of drugs: modification by discriminative stimuli of the effects of amobarbital on schedule-controlled behavior.

Food-deprived pigeons responded under a 10-min fixed-interval schedule of food presentation. During even-numbered minutes of the schedule, the discriminative stimuli were the same as those present when food was delivered. During odd-numbered minutes there was either a change in keylight color or a change in overhead illumination, either for the entire duration of the odd-numbered minutes, or for 3-sec after each response. Responding during even-numbered minutes showed the usual pattern of positive acceleration; responding during odd-numbered minutes was similarly graded, but rates were much lower. The response-rate-increasing effects of amobarbital were inversely related to control rates of responding for both even- and odd-numbered minutes. However, when the stimulus change during odd-numbered minutes was either keylight color or a change from a darkened to a brightly illuminated chamber, increases in responding were considerably less than predicted on the basis of the effects on responding during even-numbered minutes. When the stimulus change was from a darkened to a dimly illuminated chamber, control rates of responding changed little, but increases in responding during odd-numbered minutes after amobarbital were considerably greater, and of the approximate order expected on the basis of control rate.

The effects of d-amphetamine on schedule-controlled water licking in the squirrel monkey.

Three squirrel monkeys performed under a 5-min fixed-interval schedule of food presentation with licking a water-filled tube as the required operant response. All subjects developed the characteristic fixed-interval pattern of responding: an initial period of little or no responding followed by acceleration of responding to a final rate that is sustained until reinforcement. Over a range of doses, d-amphetamine had a dose-related enhancing effect on the overall rate of licking; higher doses decreased the overall rate. Analysis of the effects of d-amphetamine on the different rates within successive 30-sec periods of the interval showed that all doses in one subject and the higher doses in the two others changed the output of the licking behavior in a rate dependent way. Over a range of doses d-amphetamine not only increased the rate of licking but also the intake of water directly proportional to the number of responses. After high doses, which still increased the rate of responding, the water intake per lick decreased. The effects of d-amphetamine on licking behavior maintained under a fixed-interval schedule of food presentation were similar to the effects of amphetamine on other operant responses, such as pressing a lever or pecking a key. Schedule-controlled licking is influenced by d-amphetamine differently from drinking which is not under the control of explicit experimental consequences.

FIXED‐INTERVAL SCHEDULES OF ELECTRIC SHOCK PRESENTATION: EXTINCTION AND RECOVERY OF PERFORMANCE UNDER DIFFERENT SHOCK INTENSITIES AND FIXED‐INTERVAL DURATIONS1

In squirrel monkeys responding under a schedule in which responding postponed the delivery of electric shock, the presentation of response-dependent shock under a fixed-interval (FI) schedule increased the rate of responding. When the schedule of shock-postponement was eliminated, so that the only shocks delivered were those produced by responses under the FI schedule, a pattern of positively accelerated responding developed and was maintained over an extended period. When responses did not produce shocks (extinction), responding decreased. When shocks were again presented under the FI schedule, the previous pattern of responding quickly redeveloped. In general, response rates were directly related to the intensity of the shock presented, and inversely related to the duration of the fixed-interval. These results raise fundamental questions about the traditional classification of stimuli as reinforcers or punishers. The basic similarities among FI schedules of food presentation, shock termination, and shock presentation strengthen the conclusion that the schedule under which an event is presented and the characteristics of the behavior at the time the event is presented, are of overriding importance in determining the effect of that event on behavior.