首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献,搜索用时 31 毫秒
1.
In this paper we investigate how amphetamine affects performance in a PI task by comparing two analyses of responding during peak trials. After training on 24 s fixed interval (FI-24) with 96 s peak trials, rats were given amphetamine for 4 consecutive days at doses of .5 and 1.0 mg/kg. Responses during peak trials were fitted with a Gaussian distribution to estimate the expected time of reinforcement from the peak time. A single trials analysis was also performed to determine the start time and stop time of the transition into and out of a high rate of responding on each peak trial. Amphetamine significantly decreased peak times as measured with the Gaussian curve fitting. However, in the single trials analysis, animals initiated responding significantly earlier, but did not stop responding earlier. Thus, fitting a Gaussian to the average performance across trials sometimes provides a different characterization of the timing process than does analyzing the start and stop of responding on individual trials. In the current experiment, the latter approach provided a more precise characterization of the effects of amphetamine on response timing.  相似文献   

2.
A common procedure for studying the ability of animals to time is the peak procedure. With the peak procedure, animals are first trained on a fixed interval schedule (i.e., 30s). After the animals have been well trained on the fixed interval schedule, probe trials are introduced. On probe trials, the stimulus is presented longer (i.e., 90s) and the animal does not receive reinforcement for responding. When animals are first presented with probe trials responding remains flat following the point that reinforcement normally occurs on fixed interval trials. The descending slope that eventually emerges is acquired with experience with probe trials. The present experiments manipulated the percentage of probe trials compared to FI trials across groups of rats. It was hypothesized that the descending limb of peak responding would be acquired more quickly when there were many probe trials per session as this might facilitate extinction of responding beyond the interval that reinforcement normally occurs. It was found, however, that acquisition of peak responding occurred best when there were few probe trials per session.  相似文献   

3.
Across two experiments, a peak procedure was used to assess the timing of the onset and offset of an opportunity to run as a reinforcer. The first experiment investigated the effect of reinforcer duration on temporal discrimination of the onset of the reinforcement interval. Three male Wistar rats were exposed to fixed-interval (FI) 30-s schedules of wheel-running reinforcement and the duration of the opportunity to run was varied across values of 15, 30, and 60s. Each session consisted of 50 reinforcers and 10 probe trials. Results showed that as reinforcer duration increased, the percentage of postreinforcement pauses longer than the 30-s schedule interval increased. On probe trials, peak response rates occurred near the time of reinforcer delivery and peak times varied with reinforcer duration. In a second experiment, seven female Long-Evans rats were exposed to FI 30-s schedules leading to 30-s opportunities to run. Timing of the onset and offset of the reinforcement period was assessed by probe trials during the schedule interval and during the reinforcement interval in separate conditions. The results provided evidence of timing of the onset, but not the offset of the wheel-running reinforcement period. Further research is required to assess if timing occurs during a wheel-running reinforcement period.  相似文献   

4.
It has been shown in previous research [Kaiser, D.H., 2008. The proportion of fixed interval trials to probe trials affects acquisition of the peak procedure fixed interval timing task. Behav. Process., 77 (1), 100-108] that rats acquired peak responding sooner when fewer peak trials were presented during sessions of training with the peak procedure timing task. One potential problem with that research was that there were large differences in response rates among the groups. The present experiment attempted to examine the effect of proportion of peak trials when differences in response rate were controlled. Two groups of rats were each simultaneously tested with two versions of the peak procedure. One group was tested with 10% peak trials per session, and the other group was tested with 50% peak trials per session. For both of the groups, one of the panel lights and levers was associated with the traditional peak procedure. The other panel light and lever was associated with a similar peak procedure; however, reinforcement was provided at the end of each peak trial. This manipulation eliminated differences in response rate among the groups, however, Group 10% acquired peak responding more quickly than Group 50%, effectively replicating previous work in the absence of a response bias.  相似文献   

5.
The peak procedure is widely used in the study of interval timing with animals. Multiple timing measures can be derived from peak responding. These measures are typically presented as averages across many trials based on the implicit assumption that peak responding is stable throughout the session. We tested this assumption by examining whether peak responding changed over the course of the session in 45 mice that were trained on a fixed-interval 30-s schedule. All common measures of peak responding, except stop times, changed over the course of the session: start times increased, response rates and spreads decreased, and, although less reliably, peak times also shifted rightward. These results are congruent with a motivational interpretation, whereby increased satiety leads to the observed behavioral signature of within-session modulation of timed anticipatory responding.  相似文献   

6.
Rats were trained on mixed-fixed-interval (FI) schedules, with component FIs of 30 and 60s. The probability of reinforcement according to FI 30s varied between conditions, across values of 0.1, 0.3, 0.5, 0.7 and 0.9. When response rate in the 60s intervals was measured, separate response peaks, one close to 30s, the other at 60s, could be identified when the probability of reinforcement at 30s was 0.3 or greater. Nonlinear regression found that the location of the earlier peak was always close to 30s, that the coefficient of variation of the response functions at 30 and 60s were unaffected by reinforcement probability, but that the 30s component appeared to be timed slightly more precisely than the 60s one. Response rate at around 30s increased with increasing probability of reinforcement according to FI 30s, but responding at 60s was unaffected by reinforcement probability. The data are discussed with respect to a number of contemporary models of animal timing (scalar expectancy theory, the Behavioural Theory of Timing and the Learning to Time model), and a recent account of response output on FI-like schedules.  相似文献   

7.
Partial reinforcement often leads to asymptotically higher rates of responding and number of trials with a response than does continuous reinforcement in pigeon autoshaping. However, comparisons typically involve a partial reinforcement schedule that differs from the continuous reinforcement schedule in both time between reinforced trials and probability of reinforcement. Two experiments examined the relative contributions of these two manipulations to asymptotic response rate. Results suggest that the greater responding previously seen with partial reinforcement is primarily due to differential probability of reinforcement and not differential time between reinforced trials. Further, once established, differences in responding are resistant to a change in stimulus and contingency. Secondary response theories of autoshaped responding (theories that posit additional response-augmenting or response-attenuating mechanisms specific to partial or continuous reinforcement) cannot fully accommodate the current body of data. It is suggested that researchers who study pigeon autoshaping train animals on a common task prior to training them under different conditions.  相似文献   

8.
In Skinner's Reflex Reserve theory, reinforced responses added to a reserve depleted by responding. It could not handle the finding that partial reinforcement generated more responding than continuous reinforcement, but it would have worked if its growth had depended not just on the last response but also on earlier responses preceding a reinforcer, each weighted by delay. In that case, partial reinforcement generates steady states in which reserve decrements produced by responding balance increments produced when reinforcers follow responding. A computer simulation arranged schedules for responses produced with probabilities proportional to reserve size. Each response subtracted a fixed amount from the reserve and added an amount weighted by the reciprocal of the time to the next reinforcer. Simulated cumulative records and quantitative data for extinction, random-ratio, random-interval, and other schedules were consistent with those of real performances, including some effects of history. The model also simulated rapid performance transitions with changed contingencies that did not depend on molar variables or on differential reinforcement of inter-response times. The simulation can be extended to inhomogeneous contingencies by way of continua of reserves arrayed along response and time dimensions, and to concurrent performances and stimulus control by way of different reserves created for different response classes.  相似文献   

9.
The procedures for classical and operant conditioning, and for many timing procedures, involve the delivery of reinforcers that may be related to the time of previous reinforcers and responses, and to the time of onsets and terminations of stimuli. The behavior resulting from such procedures can be described as bouts of responding that occur in some pattern at some rate. A packet theory of timing and conditioning is described that accounts for such behavior under a wide range of procedures. Applications include the food searching by rats in Skinner boxes under conditions of fixed and random reinforcement, brief and sustained stimuli, and several response-food contingencies. The approach is used to describe how multiple cues from reinforcers and stimuli combine to determine the rate and pattern of response bouts.  相似文献   

10.
Pigeons were studied in an extension of a study by Aum et al. [Aum, S., Brown, B.L., Hemmes, N.S. 2004. The effects of concurrent task and gap events on peak time in the peak procedure. Behav. Process. 65, 43-56] on timing behavior under a discrete-trial fixed-interval (FI) procedure during which 6-s intruded events were superimposed on peak-interval (PI) test trials. In Aum et al., one event consisted in termination of the timing cue (gap trial); the other was a stimulus in the presence of which subjects had been trained to respond under an independent random-interval (RI) schedule of reinforcement (concurrent task trial). Aum et al. found a disruption of timing on concurrent task trials that was greater than that on gap trials. The present study investigated history of reinforcement associated with intruded events as a possible explanation of this earlier finding. After training to peck a side key on a 30-s PI procedure, discrimination training was conducted on the center key in separate sessions; red or green 6-s stimuli were associated with RI 24s or EXT (extinction) schedules. During testing under the PI procedure, three types of intruded events were presented during probe trials--the stimulus associated with the RI (S+) or EXT (S-) schedule during discrimination training, or a gap (termination of the side-keylight). Intruded events occurred 3, 9, or 15s after PI trial onset. Effects of reinforcement history were revealed as substantial disruption of timing during the S+ event and relatively little disruption during the S- event. Intermediate effects were found for the gap event. Results indicate that postcue effects are at least partially responsible for the disruptive effects of the S+ event.  相似文献   

11.
Quiescent cells of the central zone region of the rat lens epithelium were stimulated to enter the proliferation cycle by wounding. RNA synthesis and a corresponding increase in poly(A)+/total RNA reached a peak by Hour 4. Cells progressed into the G1B compartment by Hour 10. A rise in protein synthesis began at Hour 8, and onset of DNA synthesis occurred by Hour 14. The timing of cell cycle progression that allowed escape from a dose of X irradiation that completely inhibited DNA synthesis was investigated. A growth-arrest point was identified at Hour 9 where 10 GY of X irradiation given before, but not after, completely inhibited earliest responding cells from entering DNA synthesis on schedule. Increased quantities of cells entered DNA synthesis on schedule as timing of the X irradiation was moved closer to the end of G1. Based on time relationships, the rise in protein synthesis is correlated with the "sufficient" event for the escape.  相似文献   

12.
MPR     
Mathematical Principles of Reinforcement (MPR) is a theory of reinforcement schedules. This paper reviews the origin of the principles constituting MPR: arousal, association and constraint. Incentives invigorate responses, in particular those preceding and predicting the incentive. The process that generates an associative bond between stimuli, responses and incentives is called coupling. The combination of arousal and coupling constitutes reinforcement. Models of coupling play a central role in the evolution of the theory. The time required to respond constrains the maximum response rates, and generates a hyperbolic relation between rate of responding and rate of reinforcement. Models of control by ratio schedules are developed to illustrate the interaction of the principles. Correlations among parameters are incorporated into the structure of the models, and assumptions that were made in the original theory are refined in light of current data.  相似文献   

13.
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, midway, and at the end of an ascending and descending series of nine frequencies, ranging from 13 to 37 Hz. These stimuli appeared for 15-s periods with no food available (extinction). Gradients of responding to flicker values in the ascending series differed from those in the descending series, showing displacements in peak responding toward the lower and higher frequency values, respectively. The same effects occurred when the sequence was changed so that a descending series was followed by an ascending series of frequencies. These effects are consonant with an adaptation level (AL) interpretation and were replicated in a second experiment in which durations of the extinction presentations were increased to 30s. In a final condition, only a descending series was presented and displacement of peak responding from 25 Hz to a higher frequency stimulus, 28 Hz, was observed.  相似文献   

14.
The pattern of responding on a peak-interval timing task allows one to make inferences regarding the sources of variation that contribute to interval timing behavior. Non-temporal factors such as impulsivity may impact the validity of these inferences. Rats were trained on a 15s peak-interval procedure (PI) or a mixed 15s behaviorally dependent variable-interval, 15s peak-interval procedure (bdVIPI) for an extended number of sessions. Extended training on the PI revealed a bi-modal distribution in the times at which subjects started responding for temporally predictable reinforcement, suggesting that multiple processes contribute to the behavioral pattern obtained in this procedure. Training on the bdVIPI eliminated the early mode of this bi-modal distribution, thereby decreasing the variation in start times. These results suggest that alternative response options can modulate the influence of impulsivity in timing tasks.  相似文献   

15.
After training under a variable-interval 60-s schedule of reinforcement, four rats were exposed to 30-min extinction tests, which occurred either at the start or at the end of the session (each session being 50-min long). Response rate in extinction decreased when the extinction test occurred at the end of the session, but first increased and then decreased when the extinction test occurred at the start of the session. Consistent with other recent results, this finding suggests that some variable, other than reinforcement, contributes to early-session increases in responding.  相似文献   

16.
Two groups of 20 Ss each run individually in a soundproff chamber heated to 115 F and humidified to 100%. Ss in the experimental group received brief presentation of cool air contingent upon wmitted GSRs during 20 min of acquisition. Control Ss were matched on at a time in operant rate and were yoked one at a time to receive the cool air on a response-independent schedule. Both groups increased significantly in rate of unelicited GSRs during acquisition, with the experimental Ss' curve rising more rapidly and both groups attaining equivalent terminal levels. During extinction, the groups maintained high levels of responding and did not differ. Examination of basal skin conductance data ruled our an activation hypothesis. In the control Ss, terminal response frequency was significantly correlated with percentage of fortuitous response-contigent reinforcement. It was concluded that both croups were conditioned, with the controls receiving intermittent reinforcement sufficiently often to elevate their responding. The cool air was judged to be an effective reinforcer of unelicited GSRs, perhaps more effective than those used in previous studies.  相似文献   

17.
Reward magnitude and timing in pigeons   总被引:1,自引:0,他引:1  
We investigated the interaction of motivation and timing by manipulating the expected reward magnitude during a peak procedure. Four pigeons were tested with three different reward magnitudes, operationalized as duration of food access. Each stimulus predicted a different reward magnitude on a 5 s fixed-interval schedule. Trials with different reward magnitudes were randomly intermingled in a session. Most pigeons responded less often and started responding later on peak trials when a smaller reward was expected, but showed no differences in response termination or peak times. Reward magnitude was independently corroborated through unreinforced choice trials, when pigeons chose between the three stimuli presented simultaneously. These results contribute to a growing body of evidence that the expected reward magnitude influences the decision to start anticipatory responding in tasks where the reward becomes available after a fixed interval, but does not alter peak times, nor the decision to stop responding on peak trials.  相似文献   

18.
Previous studies have shown that amphetamine significantly alters operant responding on the behavior maintained on a schedule of differential reinforcement of low-rate (DRL). As such, behavioral deficiency of DRL responding has been observed by the drug-induced increase of non-reinforced responses and a leftward shift of inter-response time (IRT) curve on DRL responding in the rat. However, the neurochemical basis for amphetamine-induced DRL behavioral alternations remain to be elucidated. The present study was then designed to examine whether the effects of amphetamine were dependent on dopamine-subtyped receptors, this was carried out by the co-administration of the selective D1 and D2 receptor antagonists, SCH23390 and raclopride respectively. Rats were first trained to perform on DRL 10-sec task and then divided into four groups, which received separate types of double injections before the behavioral session. The four groups were the saline control group, the amphetamine alone group, the dopamine antagonist alone group, and the combination of [corrected] amphetamine and dopamine antagonist group. The saline control group performed DRL responding in an efficient manner with a major index for the peak time of the IRT curve, which was fairly localized within the 10-sec bin throughout the test phase. The subjects injected with amphetamine (1 mg/kg) significantly shortened IRT that led to a leftward shift of IRT curve, which was further revealed by a decreased peak time without significant effectiveness on the peak rate and burst response. Even though the group given SCH23390 or raclopride alone showed profound disruption on DRL behavior by flattening the IRT curve, the co-administration of amphetamine with SCH23390 or raclopride reversed the aforementioned amphetamine-induced behavioral deficiency on DRL task. Together, these results suggest that the dopamine D1 and D2 receptors are involved and important to the temporal regulation of DRL response under psychostimulant drug treatment. Furthermore, this highlights the involvement of the brain dopamine systems in the temporal regulation of DRL behavior performance.  相似文献   

19.
Two experiments with rats were conducted to study interval time-place learning when the spatiotemporal contingencies of food availability were more similar to those likely to be encountered in natural environments, than those employed in prior research. In Experiment 1, food was always available on three levers on a variable ratio (VR) 35 schedule. A VR8 schedule was in effect on Lever 1 for 5 min, then on Lever 2 for 5 min, and so forth. While rats learned to restrict the majority of their responding to the lever that provided the highest density of reinforcement, they seemed to rely on a win-stay/lose-shift strategy rather than a timing strategy. In Experiment 2, the four levers provided food on variable ratios of 15, 8, 15, and 30, each for 3 min. As expected the rats learned these contingencies. A novel finding was that the rats had a spike in response rate immediately following a change from a higher to lower reinforcement density. It is concluded that rats exposed to spatiotemporal contingencies behave so as to maximize the rate of obtained reinforcement.  相似文献   

20.
We investigated how the common measures of timing performance behaved in the course of training on the peak procedure in C3H mice. Following fixed interval (FI) pre-training, mice received 16 days of training in the peak procedure. The peak time and spread were derived from the average response rates while the start and stop times and their relative variability were derived from a single-trial analysis. Temporal precision (response spread) appeared to improve in the course of training. This apparent improvement in precision was, however, an averaging artifact; it was mediated by the staggered appearance of timed stops, rather than by the delayed occurrence of start times. Trial-by-trial analysis of the stop times for individual subjects revealed that stops appeared abruptly after three to five sessions and their timing did not change as training was prolonged. Start times and the precision of start and stop times were generally stable throughout training. Our results show that subjects do not gradually learn to time their start or stop of responding. Instead, they learn the duration of the FI, with robust temporal control over the start of the response; the control over the stop of response appears abruptly later.  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号