Within-subjects positive and negative contrast effects in rats.

Abstract

Rats were given alternating 1-min. access periods to 2 tubes containing either 32% or 4% sucrose solutions for daily 6-min. test sessions. Lick rate for 32% was higher under comparison (32 vs. 4) than noncomparison (32 vs. 32) conditions; and lick rate for 4% was lower under comparison conditions (4 vs. 32) than under noncomparison conditions (4 vs. 4). All sucrose conditions were varied within subjects and both positive and negative contrast were obtained with a small n. In addition to lick rate, intake and latency measures also revealed contrast effects. Deprivation conditions altered latency but not lick rate measures of contrast. Reducing the test session to 3 min. (alternating 30-sec. access periods) did not greatly affect contrast. Additional experiments provided evidence for distinct withindays and between-days contrast effects, as well as a between-groups contrast effect.

Successive Negative Contrast as a Function of Deprivation Condition Following Shifts in Sucrose Concentration

“…At present, data supporting this idea are somewhat equivocal. Flaherty and Largen (1975) found large positive contrast effects that did not diminish over the course of the study in ad libitum rats. Panskepp and Trowill (1971), however, found large but transitive positive contrast in low-drive subjects.…”

“…Following the second shift in the present study, the ad lib group again showed a durable contrast effect which did not dissipate over days and appeared to be as large or larger than contrast shown following the first shift. Flaherty and Largen (1975), using 32% and 4% sucrose solutions, also reported a tendency for ad libitum animals to show increased negative contrast following repeated shifts in a within-subject contrast paradigm. Using a similar within-subject procedure, Panskepp and Trowill (1971) also found a negative contrast effect in low-drive animals following a reduction in sucrose, but contrast shown by low-drive subjects was, if anything, less durable than that of high-drive subjects.…”

Role of gustatory thalamus in anticipation and comparison of rewards over time in rats

“…Indeed, in each case, the role of the gustatory thalamus has been assessed when comparing 0.15% saccharin to 1.0 M sucrose. In the simultaneous contrast paradigm, the rewards are compared within a daily session over a relatively short time frame (5,14). Specifically, the rats are given a total of three alternating 60-s access periods to each of the two levels of reward within a daily session (41).…”

Effects of alcohol and saccharin deprivations on concurrent ethanol and saccharin operant self-administration by alcohol-preferring (P) rats

“…Thus, P rats given concurrent operant access to EtOH and sucrose display a 'positive contrast' in selfadministration behaviors. Positive-contrast is a well established learning phenomenon in which animals given two reinforcers increases the self-administration of both reinforcers compared to levels of self-administration when only a single reinforcer is available (Flaherty and Largen, 1975). In addition, P rats given concurrent access to sucrose and EtOH in operant situations will self-administer concentrations of EtOH that are not self-administered when EtOH is paired with water (e.g., P rats will self-administered 45 and 60% EtOH when 2% sucrose is concurrently available).…”