2013 Basic Research: Derek Pope

Auburn University

The study supported by this grant concerns differences in delay discounting between BALB/c and C57Bl/6 mice. BALB/c mice display greater sensitivity to reinforcer magnitude and discount at a much higher rate than C57Bl/6 mice. Researchers were interested in how systematic environmental manipulations could help explain the mechanisms responsible for these differences. The findings of the study suggest that phenotypic differences in discount rates between these two strains depend, in part, on the presence of delay-correlated stimuli. They may also suggest that discount rate or delay sensitivity is more affected by events other than the delays to reward and may imply that the prevailing stimuli are signaling different aspects of the procedural context for each strain. Researchers hypothesized that the effects of d-amphetamine on delay discounting would depend not only on the strain of mouse in question, but also the stimulus conditions correlated with the contingencies maintaining choice. Preliminary findings show that for BALBs, amphetamine reduced both delay and magnitude sensitivity in a dose-dependent fashion regardless of which schedule was in effect. For C57s, d-amphetamine increased delay and magnitude sensitivity under the mixed schedule, but decreased delay and magnitude sensitivity under the multiple schedule.  


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