Abstract
Individual differences or vulnerabilities must exist which bias some individuals toward psychopathology while others remain resilient in the face of trauma. Recent work has studied the effects of uncertainty on individuals expressing behavioral inhibition (BI). The current study extended this work with uncertainty to Wistar Kyoto (WKY) rats which are a behaviorally inhibited inbred strain that models learning vulnerabilities for anxiety disorders and posttraumatic stress disorder (PTSD). WKY rats exhibit superior avoidance performance in a signaled bar press avoidance task in which a tone conditioned stimulus (CS) signals a foot shock unconditional stimulus (US) when compared with non-inhibited Sprague-Dawley (SD) rats. In addition, WKY rats express enhanced eyeblink conditioning. Recent work with behaviorally inhibited humans has indicated that this enhanced eyeblink conditioning is more evident in conditions that insert CS- or US-alone trials into CS-US paired training, resulting in uncertain and suboptimal learning conditions. The current study examined the effects of partial predictability training, in which the CS signaled the US only one-half of the time, on the acquisition and expression of avoidance. Standard training with a fixed 60-s CS which predicted shock on 100% of trials was compared with training in which the CS predicted shock on 50% of trials (partial predictability) using a pseudorandom schedule. As expected, WKY rats acquired avoidance responses faster and to a greater degree than SD rats. Partial predictability of the US essentially reduced SD rats to escape responding. Partial predictability also reduced avoidance in WKY rats; however, adjusting avoidance rates for the number of potential pairings of the CS and US early in training suggested a similar degree of avoidance expression late in the last session of training. Enhanced active avoidance expression, even in uncertain learning conditions, can be interpreted as behaviorally inhibited WKY rats responding to the expectancy of the shock by avoiding, whereas non-inhibited SD rats were responding to the presence of the shock by escaping. Future work should explore how WKY and SD rats as well as behaviorally inhibited humans acquire and extinguish avoidance responses in uncertain learning situations.
Highlights
Since most individuals who experience a traumatic event do not go on to develop post-traumatic stress disorder (PTSD), individual differences or vulnerabilities must exist that bias some individuals toward psychopathology while others remain resilient in the face of trauma
receiver operator curves (ROCs) analysis suggests that active coping with stressors with partial predictability is as strong a strain characteristic as inhibited temperament
The major finding of the current study was that behaviorally inhibited Wistar Kyoto (WKY) rats trained with a 50% conditioned stimulus (CS)-alone schedule of partial predictability outperformed non-inhibited SD rats trained with a 100% CS-unconditional stimulus (US) schedule
Summary
Since most individuals who experience a traumatic event do not go on to develop post-traumatic stress disorder (PTSD), individual differences or vulnerabilities must exist that bias some individuals toward psychopathology while others remain resilient in the face of trauma. Pre-trauma intolerance of uncertainty predicts PTSD symptoms [5], intolerance of uncertainty is a moderator between worry and PTSD hyperarousal symptoms [6], and intolerance of uncertainty is related to all symptoms of PTSD except re-experiencing [7] Another such vulnerability that has received much attention is avoidance, in which an individual takes effortful steps to alter the form and/or frequency of events that may be tied to experiences evoking anxiety-like responses [8]. Exaggerated avoidance would be especially maladaptive in uncertain situations in which an aversive event has a low chance to occur In these situations, the individual may express high levels of avoidance. In its various forms, is a core feature of anxiety disorders, posttraumatic stress disorder (PTSD), and obsessivecompulsive disorder (OCD) and individual differences in the tendency to express avoidance to an excessive degree is a source of vulnerability to develop these psychopathologies
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