Differential reinforcement of low rates differentially decreased timing precision

Abstract

Timing processes have been implicated as potential mechanisms that underlie self-controlled choice. To investigate the impact of an intervention that has been shown to increase self-controlled choice on timing processes, accuracy and precision of temporal discrimination were assessed in an 18-s peak procedure (18-s fixed interval trials; 54-s peak trials). During an intervention phase, mice in three treatment groups experienced differential reinforcement of low rate (DRL) schedules of reinforcement of 27 s, 18 s, or 9 s. A fourth group received continued exposure to the peak procedure. After the DRL intervention, timing was reassessed using the peak procedure. In contrast to previous reports, the DRL intervention resulted in less precise timing as indicated by increased peak spread and disrupted single-trial measures of temporal control. These effects were only detected just after the DRL intervention suggesting a transient effect of DRL exposure on timing. The increase in peak spread in the present experiment suggests delay exposure via DRL schedules may produce a "dose-dependent" effect on temporal discrimination, which may also increase self-controlled choice.

Keywords: DRL intervention; Interval timing; Mice; Peak procedure.

Fig. 1

Inter-response time (IRT) histograms for each group during the last five sessions of the differential reinforcement of low rate (DRL) intervention. Each panel shows histograms for different DRL groups as indicated in the bottom right. Bars show group means.

Fig. 2

Average peak trial response distributions for each group across select time points. The bottom right of each panel denotes the selected time point with session number in parentheses. Data points represent averages of five sessions within groups.

Fig. 3

Gaussian parameter estimates of peak spread and peak time for each group. Estimates were derived for the two blocks of 5 sessions before the differential reinforcement of low rate (DRL) intervention and for each block of 5 sessions after DRL. Data represent means (+/− SEM). Asterisks (*) denote values that were significantly (p < .05) different than Pre-DRL (−1) baseline average.

Fig. 4

Single trial measures for the last 10 Pre-DRL sessions and the first 10 Post-DRL sessions for each group. Data points represent group means.

Fig. 5

Average peak spread during the first 10 Post-DRL sessions as a function of reinforcement rate during the last five DRL sessions. Dotted lines show the line of best fit for each group.