Extinction learning is slower, weaker and less context specific after alcohol

Abstract

Alcohol is frequently involved in psychological trauma and often used by individuals to reduce fear and anxiety. We examined the effects of alcohol on fear acquisition and extinction within a virtual environment. Healthy volunteers were administered alcohol (0.4g/kg) or placebo and underwent acquisition and extinction from different viewpoints of a virtual courtyard, in which the conditioned stimulus, paired with a mild electric shock, was centrally located. Participants returned the following day to test fear recall from both viewpoints of the courtyard. Skin conductance responses were recorded as an index of conditioned fear. Successful fear acquisition under alcohol contrasted with impaired extinction learning evidenced by persistent conditioned responses (Experiment 1). Participants' impairments in extinction under alcohol correlated with impairments in remembering object-locations in the courtyard seen from one viewpoint when tested from the other viewpoint. Alcohol-induced extinction impairments were overcome by increasing the number of extinction trials (Experiment 2). However, a test of fear recall the next day showed persistent fear in the alcohol group across both viewpoints. Thus, alcohol impaired extinction rather than acquisition of fear, suggesting that extinction is more dependent than acquisition on alcohol-sensitive representations of spatial context. Overall, extinction learning under alcohol was slower, weaker and less context-specific, resulting in persistent fear at test that generalized to the extinction viewpoint. The selective effect on extinction suggests an effect of alcohol on prefrontal involvement, while the reduced context-specificity implicates the hippocampus. These findings have important implications for the use of alcohol by individuals with clinical anxiety disorders.

Keywords: Alcohol; Extinction; Fear memory.

Fig. 1

Fear memory was tested in a virtual reality environment. (A) Illustration of the virtual courtyard from above showing the starting location of each trial (A) and locations from which acquisition and extinction were performed (B or C, with corresponding viewpoints from each location). (D) The general procedure involved fear acquisition on day 1 from one viewpoint (B or C; dark shading) and extinction from the other viewpoint (light shading). A test of fear recall was performed on day 2 with interleaved presentations of the CS+ and CS− from each viewpoint.

Fig. 2

Experiment 1, mean normalized and range-corrected skin conductance responses for fear acquisition and extinction on day-1 and recall from acquisition and extinction viewpoints on day-2 as a function of treatment group. Each block represents the mean of 2 trials of learning. Error bars represent SEM.

Fig. 3

Mean percentage of correctly recognized object locations as a function of condition and group for (A) same-view and (B) shifted-view performance in Experiment 1. Error bars represent SEM.

Fig. 4

Experiment 2, mean normalized skin conductance responses for fear acquisition and extinction on day-1 and recall from both acquisition and extinction viewpoints on day-2 as a function of treatment group. Each block consists of 2 trials of learning. Error bars represent SEM.