Extinction in multiple virtual reality contexts diminishes fear reinstatement in humans

Abstract

Although conditioned fear can be effectively extinguished by unreinforced exposure to a threat cue, fear responses tend to return when the cue is encountered some time after extinction (spontaneous recovery), in a novel environment (renewal), or following presentation of an aversive stimulus (reinstatement). As extinction represents a context-dependent form of new learning, one possible strategy to circumvent the return of fear is to conduct extinction across several environments. Here, we tested the effectiveness of multiple context extinction in a two-day fear conditioning experiment using 3-D virtual reality technology to create immersive, ecologically-valid context changes. Fear-potentiated startle served as the dependent measure. All three experimental groups initially acquired fear in a single context. A multiple extinction group then underwent extinction in three contexts, while a second group underwent extinction in the acquisition context and a third group underwent extinction in a single different context. All groups returned 24h later to test for return of fear in the extinction context (spontaneous recovery) and a novel context (renewal and reinstatement/test). Extinction in multiple contexts attenuated reinstatement of fear but did not reduce spontaneous recovery. Results from fear renewal were tendential. Our findings suggest that multi-context extinction can reduce fear relapse following an aversive event--an event that often induces return of fear in real-world settings--and provides empirical support for conducting exposure-based clinical treatments across a variety of environments.

Keywords: Anxiety; Extinction; Fear conditioning; Fear-potentiated startle; Virtual reality.

Figure 1

Experimental design. Fear conditioning (Acquisition) was performed identically across three experimental groups on Day 1. During Extinction on the same day, one group (ABC) received extinction training in three virtual contexts, whereas the two other groups extinguished in a single virtual context -- either in the fear conditioning context (Group A) or a novel context (Group B). On Day 2, which took place 24 hrs following Extinction, participants came back for tests of Spontaneous Recovery, Renewal and Reinstatement. Numbers below Acquisition indicate the number of trials that were reinforced by a shock and those that were not. The conditioned stimuli were never reinforced during the other portions of the experiment. CS+ = reinforced conditioned stimulus, CS− = unreinforced conditioned stimulus, ITI = inter-trial interval.

Figure 2

Fear-potentiated startle results from Acquisition and Extinction (Day 1) and Spontaneous Recovery and Renewal (Day 2). (a) Subjects in all three groups exhibited greater responses to the CS+ (reinforced conditioned stimulus) versus the CS− (unreinforced conditioned stimulus) during fear conditioning, indicating successful acquisition of conditioned fear. (b) By late extinction, there were no differences in responses between the CS+ versus the CS− in any group, indicating successful immediate fear extinction on Day 1. (c) All groups exhibited spontaneous recovery when tested in the extinction context. Note that Group ABC was tested for spontaneous recovery in the acquisition context (A). (d) There was little evidence of fear renewal following the recovery test. ** denotes P < .001, * denotes P < .05. ITI = probes presented during intertrial interval.

Figure 3

Fear-potentiated startle results from the Reinstatement test (Day 2). (a) Reinstatement evoked enhanced responses to the CS+ (reinforced conditioned stimulus) versus the CS− (unreinforced conditioned stimulus) in Group A and Group B, but not in Group ABC. (b) Difference scores (CS+ minus CS−) were calculated for each subject for acquisition and reinstatement. Difference scores from acquisition were subtracted from reinstatement to yield a fear-retention index, where positive values indicate an increase in differential fear from acquisition to reinstatement and negative values indicate a decrease in differential fear. While Group A and Group B exhibited similar levels of differential responding between acquisition and reinstatement test, subjects in Group ABC showed a significant decline in startle. ** denotes P < .001, * denotes P < .05. ITI = baseline startle probes presented during the intertrial interval.