Using context to resolve temporal ambiguity

Abstract

Three conditioned lick suppression experiments with rats examined the role of the context in the selection and integration of independently acquired interval relationships. In Experiment 1, rats were exposed to separate conditioned stimuli 1 and 2 (CS1-CS2) pairings with 2 different interval relationships, each in its own distinctive context, X or Y. The resultant integration was determined by the training context (X or Y) in which unconditioned stimulus (US)-CS2 backward pairings occurred, as assessed in a third neutral context (Z). In Experiment 2, rats experienced CS1-CS2 pairings with 2 different interval relationships as in Experiment 1, and then received US-CS2 pairings in both contexts X and Y. The testing context (i.e., X or Y) determined the resultant integration. In Experiment 3, rats were exposed to CS1-CS2 pairings in 2 different interval relationships each in different phases (i.e., Phases 1 and 2), and then in Phase 3 received US-CS2 pairings. The temporal context of testing (i.e., short or long retention interval) determined the resultant integration. Thus, both physical and temporal context can be used to disambiguate conflicting temporal information.

Figure 1

Design and hypothetical interval representation of Experiment 1. The light gray and the white squares represent cues CS1 (a 3-s click train) and CS2 (a 3-s tone), respectively. Footshock unconditioned stimuli (1.0-mA for 0.5-s) are represented by black rectangles under the time line. The ISI between the termination of CS1 and the onset of CS2 was either 5 s (denoted by large spaces between the cue CS1 and the cue CS2 representations) or 0 s (denoted by the lack of space between the cue CS1 and the cue CS2 representations). The ISI between the termination of the US and the onset of CS2 was 4.5 s. “/” means “unpaired with”; “CR” and “cr” indicate the expectation of robust and weak conditioned response, respectively, based on the TCH and Miller and Escobar's (2002) retrieval model.

Figure 2

Results of Experiment 1. Mean suppression to CS1 for both Groups X and Y, respectively. Error bars represent the standard error of the mean.

Figure 3

Design and hypothetical interval representation of Experiment 2. The light gray and the white squares represent cues CS1 (a 3-s click train) and CS2 (a 3-s tone), respectively. Footshock unconditioned stimuli (1.0 mA for 0.5 s) are represented by black rectangles under the time line. The ISI between the termination of CS1 and the onset of CS2 was either 5 s (denoted by large spaces between the cue CS1 and the cue CS2 representations) or 0 s (denoted by the lack of space between the cue CS1 and the cue CS2 representations). The ISI between the termination of the US and the onset of CS2 was 4.5 s. “/” means “unpaired with”; “CR” and “cr” indicate the expectation of robust and weak conditioned response, respectively, based on the TCH and Miller and Escobar's (2002) retrieval model.

Figure 4

Results of Experiment 2. Mean suppression to CS1 for both Groups X and Y, respectively. Error bars represent the standard error of the mean.

Figure 5

Design and hypothetical interval representation of Experiment 3. CS1 = a 3-s click train) and CS2 = a 3-s tone, respectively. US = footshock unconditioned stimuli (1.0 mA for 0.5 s) is indicated by black rectangles. The ISI between the termination of CS1 and the onset of CS2 was either 5 s (denoted by large space between the cue CS1 and the cue CS2 representations) or 0 s (denoted by the lack of spaces between the cue CS1 and the cue CS2 representations). The ISI between the termination of the US and the onset of CS2 was 4.5 s. “CR” and “cr” indicate the expectation of robust and weak conditioned response, respectively. Based on the TCH and Miller and Escobar's (2002) retrieval model. The designations “TD” and “DT” refer to the interval arrangement between CS1 and CS2 in Phases 1 and 2 (T = trace and D = delay). “Short” = short retention interval (3 days). “Long” = long retention interval (24 days).

Figure 6

Results of Experiment 3. Mean suppression to CS1 for Groups DT and TD tested after a short or a long retention interval. Error bars represent the standard error of the mean.