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| Habituation to the Reinforcer and Within-Session Changes in Responding |
| Saturday, May 29, 2004 |
| 3:30 PM–4:50 PM |
| Beacon D |
| Area: EAB/BPH; Domain: Applied Research |
| Chair: Eric S. Murphy (University of Alaska Anchorage) |
| Discussant: Frances K. McSweeney (Washington State University) |
| Abstract: . |
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| Within-Session Changes in Responding Reinforced by Water: Effects of Variability in the Duration of Reinforcement |
| KENJIRO AOYAMA (Doshisha University) |
| Abstract: This study tested the hypothesis (McSweeney & Swindell, 1999) that habituation contributes to within-session decreases in drinking. Six rats’ leverpressing was reinforced by water under a continuous reinforcement (CRF) schedule. Session length was 30-min. During the fixed amount sessions, duration of reinforcement was fixed at 3 seconds. Reinforcement duration varied from 1 to 5 seconds, with a mean of 3 seconds, during variable amount sessions. The experimental phase lasted 10 successive days and consisted of 5 fixed amount and 5 variable amount sessions, alternating day by day. Within-session decreases in responding were steeper during the fixed amount than during the variable amount sessions. A two-way repeated-measures ANOVA revealed a statistically-significant interaction between condition and 3-min block (F(9,45)=2.10, p<.05) In addition, response rates were well described as linear functions of cumulative number of reinforcements. The regression line for the fixed amount sessions had a steeper slope and a smaller x-axis intercept than those for the variable amount sessions. These results support the habituation hypothesis and are not explained by postingestive factors. |
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| Preloading with Ethanol before Sessions of Ethanol Self-Administration |
| BENJAMIN P. KOWAL (Washington State University), Frances K. McSweeney (Washington State University), Eric S. Murphy (University of Alaska Anchorage), Roberta S. Varao (Washington State University), Shea C. Bower (Washington State University) |
| Abstract: The present study asks if limited exposure to ethanol before sessions of ethanol self-administration contributes to changes in within-session responding. Five experimentally-experienced ethanol-preferring (P) rats responded on a simple variable interval (VI) 15-s schedule of reinforcement during 50 min sessions that were preceded by exposure to 0, 0.1, 0.5, 2.0, 5.0 or 15.0 ml of ethanol. Sessions were run until all subjects had been exposed to each of the preloading amounts for 5 sessions. Response rates were highest after 0.1 ml preloading. The largest amount of ethanol preloading (i.e., 15.0 ml) produced the lowest response rates. Peak responding occurred in the first 10 min for all preloading amounts. Additionally, within-session patterns of responding differed for the different preloading amounts. The present results suggest that preloading may increase the value of reinforcers presented early in sessions of self-administration of ethanol. |
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| Spontaneous Recovery and Dishabituation of Ethanol-Reinforced Responding in Alcohol-Preferring Rats |
| 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: Two experiments tested the hypothesis that habituation to the reinforcer occurs during sessions of ethanol-reinforced responding in alcohol-preferring (P) rats. In both experiments, P-rats’ leverpressing was reinforced by 5-s access to a 10% (v/v) ethanol solution on a variable interval 15-s schedule during 50 min sessions. In Experiment 1 (Spontaneous Recovery), experimental sessions were separated by 5-min, 2-hr, or 24-hr intersession intervals. Early-session rates of responding during Session 2 of the 5-min and 2-hr intersession intervals were lower than the corresponding rates of responding during Session 1. The rates and within-session patterns of responding during Sessions 1 and 2 were similar during the 24-hr inter-session interval. In Experiment 2 (Dishabituation), an extraneous stimulus (light or tone) was presented at 24 min and 55 s into the session. Rates of responding temporarily increased after both dishabituation manipulations. The results of both experiments support the idea that habituation to repeatedly-presented ethanol reinforcers occurs in P-rats. |
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