Increased generalization of learned associations is related to re-experiencing symptoms in veterans with symptoms of post-traumatic stress

Abstract

One interpretation of re-experiencing symptoms in post-traumatic stress disorder (PTSD) is that memories related to emotional information are stored strongly, but with insufficient specificity, so that stimuli which are minimally related to the traumatic event are sufficient to trigger recall. If so, re-experiencing symptoms may reflect a general bias against encoding background information during a learning experience, and this tendency might not be limited to learning about traumatic or even autobiographical events. To test this possibility, we administered a discrimination-and-transfer task to 60 Veterans (11.2% female, mean age 54.0 years) self-assessed for PTSD symptoms in order to examine whether re-experiencing symptoms were associated with increased generalization following associative learning. The discrimination task involved learning to choose the rewarded object from each of six object pairs; each pair differed in color or shape but not both. In the transfer phase, the irrelevant feature in each pair was altered. Regression analysis revealed no relationships between re-experiencing symptoms and initial discrimination learning. However, re-experiencing symptom scores contributed to the prediction of transfer performance. Other PTSD symptom clusters (avoidance/numbing, hyperarousal) did not account for significant additional variance. The results are consistent with an emerging interpretation of re-experiencing symptoms as reflecting a learning bias that favors generalization at the expense of specificity. Future studies will be needed to determine whether this learning bias may pre-date and confer risk for, re-experiencing symptoms in individuals subsequently exposed to trauma, or emerges only in the wake of trauma exposure and PTSD symptom development.

Keywords: Anxiety; associative learning; declarative memory; stress; transfer; veterans.

Figure 1

The discrimination-and-transfer test. (A) Two sample discrimination trials, with a pair of objects that differ in one relevant feature (on the top, colour is the relevant feature and on the bottom, shape is the relevant feature). (B) The subject chooses an object, which is raised; if correct, a smiley face is revealed underneath. (C) Two sample transfer phase trials, in which the irrelevant feature of each object pair is changed (on the top, shape is the irrelevant feature that has changed and on the bottom, colour is the irrelevant feature that has changed).

Figure 2

Mean errors for each of the 6 training stages of the discrimination-and-transfer task and mean errors for the transfer phase.

Figure 3

Transfer phase performance. (A) Mean errors on the transfer phase decreased with increasing number of PTSD Cluster B symptoms endorsed. (B) There was also a negative correlation between transfer errors and educational attainment.