Fig. 7.

Disrupting the medial prefrontal cortex (mPFC) reduced deliberative vicarious trial and error (VTE) behavior. A: example passes through the choice point. VTE was quantitatively measured as the integrated absolute angular velocity (IdPhi) of the rat’s head across the pass through the choice point (see methods). Large log IdPhi scores are indicative of VTE events (left column) whereas low log IdPhi scores are indicative of non-VTE (nVTE) events (right column). B: On a task with VTE trials, as in Restaurant Row, the IdPhi distribution will be positively skewed, with the size of the shoulder indicative of the proportion of VTE trials. VTE distributions for clozapine N-oxide (CNO) and vehicle (Veh) days for a rat administered designer receptors exclusively activated by designer drugs (DREADDs; DREADDs+; top) and a rat not given DREADDs (DREADDs−; bottom). C: compromising the mPFC reduced VTE behavior. D: on Restaurant Row rats can encounter “good deals” (delay < threshold), “bad deals” (delay > threshold), and “difficult decisions” (delay≈threshold). DREADDs+ rats showed reduced VTE specifically on difficult decisions. E: in contrast, no differences were seen between Veh and CNO days for DREADDs− rats. F and G: the average theta cycle size was measured for VTE and nVTE. Theta cycle size increased on VTE trials on both Veh (F) and CNO (G) days. H: the size of the theta cycle correlated with running speed; however, CNO reduced this relationship. I: we measured the phase locking of hippocampal place cells to hippocampal theta during VTE and nVTE trials. Interestingly, the proportion of significantly phase-locked cells dropped during VTE trials. J: we measured the asymmetry index (AI) of individual theta cycles for VTE and nVTE trials. VTE trials had a smaller AI than nVTE trials for both Veh and CNO trials, suggesting more nonlocal representations of space during VTE. K: we measured the length of the ascending and descending phase of VTE and nVTE trials. The duration of the ascending phase of theta cycles increased during VTE trials on Veh and CNO days. L and M: to further examine this we measured the posterior probability in relation to the rat’s location immediately behind and in front of the rat (rat is at 0). L: the posterior probability was higher for local representations on nVTE trials than VTE trials. In contrast, the decoded probability was higher for nonlocal representations in front of the rat on VTE trials (difference in the mean ± CI 99.50%). M: this relationship was not apparent on CNO days (difference in the mean ± CI 99.50%). +P < 0.08; *P < 0.05, ***P < 0.005.