Associative and temporal processes: a dual process approach

Abstract

Approaches to the study of associative learning and interval timing have traditionally diverged on methodological and theoretical levels of analysis. However, more recent attempts have been made to explain one class of phenomena in terms of the other using various single-process approaches. In this paper we suggest that an interactive dual-process approach might more accurately reflect underlying behavioral and neural processes. We will argue that timing in Pavlovian conditioning is best understood in terms of an abstract temporal code that is not a feature of the predictive stimulus (i.e., the conditioned stimulus, CS), per se. Rather, we assume that the time between the CS and the unconditioned stimulus (US) is encoded in the form of an abstract representation of this temporal interval produced as an output of a central multiple-oscillator interval timing system. As such, associations can then develop between the CS and this abstract temporal code in much the same way that the CS develops associations with different features of the US. To support the dual-process approach, we first show that exposure to a Pavlovian zero contingency procedure results in a failure to acquire new associations, not a failure to express learning due to some temporally defined performance mask. We also consider evidence that supports the abstract temporal coding idea in a US preexposure task, and, finally, present some evidence to encourage the dissociation between basic associative and temporal learning processes by exploring reward devaluation effects in a peak timing task.

Keywords: Multiple oscillators; Sensory specific associations; US devaluation; US preexposure; Zero contingency degradation.

Figure 1

Mean magazine responding is displayed during CS and Pre CS periods across 6 extinction sessions for the groups given zero or positive contingency (Zero, Pos) training followed by context extinction or not (Ctx Ext, No Ext).

Figure 2

Data from Pavlovian-to-instrumental transfer tests showing instrumental responding in 5 successive intervals during the Pre stimulus period and also during the stimulus but separated in terms of the response that was previously reinforced with the same or different outcome as that signaled by the CS. The data are shown for separate groups of rats given a different amounts of Pavlovian training in which the US was always presented either early or late in the CSs.

Figure 3

Mean magazine responding during CS presentations in the extinction test sessions after one of the USs had been devalued (CS dev) or not (CS not dev). Responding is shown in 12, successive 5-s intervals within the CS. Mean % time in the food magazine is shown in the upper panel while those data were expressed as a ratio of baseline responding in the lower panel.

Figure 4

Three different models for approaching timing in Pavlovian learning. Panel A shows a multi-component model where the CS is assumed to form distinct associations with sensory (US_S) and emotive (US_E) features of the US as well as with a representation of the time of occurrence of the US (US_T). Panel B displays a multiple oscillator model where different oscillators are assumed to have different periodicities. Panel C shows a dual process model where associations are assumed to be formed between the CS and a temporal US representation that itself is established through input from separate oscillators (Osc 1, 2, 3). The degree of activation of these temporal units is coded by their degree of shading.