Preservation of within-compound associations after blocked preexposure to two compound flavors

Three experiments investigated the extinction of the within-compound A↔X association established when two compound flavors, AX and BX, are preexposed in blocks (i.e., AX, AX, AX, ... BX, BX, BX). In Experiment 1, a group of rats received preexposure to a block of AX trials followed by a second block of BX trials (AX-BX), while a second group received blocked preexposure to the same stimuli in the opposite order (BX-AX). Subsequently, flavor A was paired with lithium chloride. This conditioning resulted in a similar reduction of consumption of flavor X in both groups. In Experiment 2 four groups of rats received blocked preexposure to AX-BX, AX-B, A-BX, or A-X. After aversive conditioning of X, consumption of A and B was significantly lower for the groups which received these flavors paired with X than for the groups for which these flavors were presented isolated. In Experiment 3 a group of rats was preexposed to a block of SaltX presentations followed by a block of BX presentations (SaltX-BX), and a second group received blocked preexposure to (BX-SaltX). After subsequent sodium depletion, consumption of X was high and similar for the SaltX-BX and for the BX-SaltX groups. These results indicate that the within-compound association established in the first block of a blocked preexposure is not extinguished when the preexposure phase is concluded.