Temporal Bisection and Effects of d-Amphetamine Administration in Lewis and Fischer 344 Rats

Abstract

Temporal Bisection and Effects of d-Amphetamine Administration in Lewis and Fischer 344 Rats Marissa Turturici Temporal control concerns the discrimination of intervals of time. Individuals with various psychological disorders have shown differences in temporal control when compared to control populations. It is unknown whether and how temporal control might be linked with impulsivity, another measure that predicts problem behavior such as attention-deficit/hyperactivity disorder. Because Lewis (LEW) rats reliably show greater impulsive choice relative to Fischer 344 (F344) rats, the present study examined responding in these two strains under a temporal-bisection procedure that assesses temporal control. In the temporal-bisection procedure, rats are trained to discriminate between two durations. Intermediate durations are subsequently presented to determine the duration at which responding is nearly equally distributed between the original training durations. This duration is the bisection point. Because LEW rats show greater impulsive choice, it was hypothesized that LEW rats would show overestimation of duration (shorter bisection points). This effect would indicate that the subjective experience of duration, or delay, is longer for LEW rats. Results indicated that LEW rats' bisection points were shorter on average than F344 rats' bisection points in the baseline phase of the experiment. The baseline difference between LEW and F344 was not replicated during a subsequent phase of the experiment, but LEW and F344 rats did show differential effects of d-amphetamine on behavior during select conditions and doses. Effects of d-amphetamine replicated previous studies that showed apparent loss of stimulus control with increasing d-amphetamine doses, as opposed to underestimation or overestimation of temporal duration. The results generally add to the evidence supporting a link between impulsivity and temporal control. Nonhuman Animal Studies .