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| Within-Session Changes in Responding |
| Saturday, May 28, 2005 |
| 1:00 PM–2:20 PM |
| Boulevard A (2nd floor) |
| Area: EAB; Domain: Basic Research |
| Chair: Benjamin P. Kowal (Washington State University) |
| Abstract: The topic of within-session changes in responding continues to receive much empirical and theoretical attention. Some of the more recent exploits from this productive research topic include examinations of within-session changes during sessions of drug self-administration and investigations into post-session events that influence within-session patterns of responding. Examinations of drug self-administration suggest that variability and behavioral history are important factors that contribute to the regulation of drug taking. Investigations manipulating post-session events suggest roles for predictable up-coming events in determining the relative value of current reinforcement. The presentation of these investigations together will provide attendees with many ideas for future research and with a better understanding of the factors that contribute to within-session changes in responding. |
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| The Effects of Post-session Wheel Running on Within-session Changes in Responding |
| KENJIRO AOYAMA (Doshisha University, Japan) |
| Abstract: This study tested the effects of post-session wheel running on within-session changes in responding. Running after the consumption of food was supposed to produce a conditioned taste aversion. Lever pressing by six rats was reinforced by a food pellet under a continuous reinforcement (CRF) schedule in 30 min sessions. Two different flavored food pellets were used as reinforcers. In the experimental sessions, lever pressing was reinforced by one of the two flavored pellets. After those sessions, the rats were placed in running wheels for 30 minutes. In the baseline sessions, the other flavored pellets reinforced lever pressing. Following baseline sessions, the rats were immediately returned to their home cages. Subjects experienced the experimental and the baseline sessions on alternate days. Total number of food pellets eaten during the experimental sessions decreased with repeated exposure to post-session wheel running. Within-session decreases in responding were observed during both experimental and baseline sessions. In addition, response rates were well described as a linear function of the cumulative number of reinforcements (R2>.98). The regression lines for the experimental sessions had smaller y- and x-axis intercepts than those for the baseline sessions. However, slopes of the regression lines for experimental and baseline sessions were similar. |
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| Does Upcoming Food-pellet Reinforcement Alter Rats' Responding on a Delayed-Matching-to-Sample Task? |
| JEFFREY N. WEATHERLY (University of North Dakota), Jeri Nurnberger (University of North Dakota), Sarah Zidon (University of North Dakota) |
| Abstract: Research from our laboratory has demonstrated that rats' rates of responding for 1% sucrose are increased if food-pellet reinforcement will be upcoming within the same session. The present study investigated whether rats' responding on a delayed-matching-to-sample (DMTS) task for 1% sucrose reinforcement would also be influenced by upcoming food pellets and, if so, whether response rate, response accuracy, or both would be influenced. Rats responded on a DMTS procedure with delays of 0, 3, or 9 s between the presentation of the sample stimulus and the choice period. Each condition was conducted once when a 20-min period of non-contingent food-pellet reinforcement would follow the 30-min DMTS period and once when it would not. Four separate experiments produced one reliable result. Upcoming food pellets increased response rates on the DMTS task, but not accuracy. Thus, upcoming food-pellet reinforcement appears to influence the speed of responding, but does not appear to alter sensitivity to other contingencies. |
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| Reinstatement of Self-administration in Ethanol Preferring Rats |
| BENJAMIN P. KOWAL (Washington State University), Frances K. McSweeney (Washington State University), Benjamin L. Lawson (Washington State University), Roberta S. Varao (Washington State University) |
| Abstract: This study determines the training histories that produce more or less responding during reinstatement. Six female ethanol-preferring (P) rats responded on tandem variable interval (VI) – differential reinforcement of paced responding (DRP) schedules during training (i.e., tandem VI 15-s, 1 to 2-s IRT DRP; VI 15-s, 3 to 4-s IRT DRP; VI 60-s, 1 to 2-s IRT DRP; VI 60-s, 3 to 4-s IRT DRP; VI 240-s, 1 to 2-s IRT DRP; VI 240-s, 3 to 4-s IRT DRP). Responding on schedules with high rates of reinforcement (e.g., tandem VI 15-s, 1 to 2-s IRT DRP) produced reliable within session decreases in responding. Responding on schedules with low rates of reinforcement (e.g., tandem VI 240-s, 1 to 2-s IRT DRP) did not result in large within session changes in responding. Low and high DRP schedules produced similar within session changes in responding. Responding during reinstatement was greater after training with high DRP schedules (i.e., 1 to 2-s IRT DRP) then after training with low DRP schedules (i.e., 3 to 4-s IRT DRP). Responding usually did not vary as a function of the rate of reinforcement during training (i.e., VI 15-s vs. VI 240-s). |
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| Within-Session Changes in Ethanol-Reinforced Responding of Alcohol-Preferring Rats During Fixed- and Variable-Interval Schedules of Reinforcement |
| ERIC S. MURPHY (University of Alaska, Anchorage), Frances K. McSweeney (Washington State University), Benjamin P. Kowal (Washington State University), Jennifer McDonald (Washington State University), Roberta S. Varao (Washington State University) |
| Abstract: Five alcohol-preferring (P) rats responded on fixed-interval (FI) and variable-interval (VI) schedules that provided programmed rates of reinforcement ranging from 60 to 480 reinforcers per hour. In all conditions, reinforcers consisted of 5-s access to a 10% ethanol solution. Rate of responding increased, decreased, or increased and then decreased within the sessions. The within-session pattern of responding changed with changes in the programmed rate of reinforcement. Within-session decreases in responding were generally steeper during the FI than during the VI schedule that delivered the same rate of reinforcement. The results of the present experiment are generally consistent with the idea that sensitization and habituation to ethanol reinforcers contribute to within-session changes in ethanol-reinforced operant responding in P-rats (e.g., McSweeney, Murphy, & Kowal, in press; Murphy, 2003). |
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