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Inhibited Personality Temperaments Translated Through Enhanced Avoidance and Associative Learning Increase Vulnerability for PTSD

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Review

Inhibited Personality Temperaments Translated Through Enhanced Avoidance and Associative Learning Increase Vulnerability for PTSD

Michael Todd Allen et al. Front Psychol.

Abstract

Although many individuals who experience a trauma go on to develop post-traumatic stress disorder (PTSD), the rate of PTSD following trauma is only about 15-24%. There must be some pre-existing conditions that impart increased vulnerability to some individuals and not others. Diathesis models of PTSD theorize that pre-existing vulnerabilities interact with traumatic experiences to produce psychopathology. Recent work has indicated that personality factors such as behavioral inhibition (BI), harm avoidance (HA), and distressed (Type D) personality are vulnerability factors for the development of PTSD and anxiety disorders. These personality temperaments produce enhanced acquisition or maintenance of associations, especially avoidance, which is a criterion symptom of PTSD. In this review, we highlight the evidence for a relationship between these personality types and enhanced avoidance and associative learning, which may increase risk for the development of PTSD. First, we provide the evidence confirming a relationship among BI, HA, distressed (Type D) personality, and PTSD. Second, we present recent findings that BI is associated with enhanced avoidance learning in both humans and animal models. Third, we will review evidence that BI is also associated with enhanced eyeblink conditioning in both humans and animal models. Overall, data from both humans and animals suggest that these personality traits promote enhanced avoidance and associative learning, as well as slowing of extinction in some training protocols, which all support the learning diathesis model. These findings of enhanced learning in vulnerable individuals can be used to develop objective behavioral measures to pre-identify individuals who are more at risk for development of PTSD following traumatic events, allowing for early (possibly preventative) intervention, as well as suggesting possible therapies for PTSD targeted on remediating avoidance or associative learning. Future work should explore the neural substrates of enhanced avoidance and associative learning for behaviorally inhibited individuals in both the animal model and human participants.

Keywords: PTSD; associative learning; avoidance learning; eyeblink conditioning; personality temperaments; rat model.

Figures

Figure 1
Figure 1
Acquisition and extinction of avoidance responses in response to tone that precedes a foot shock in WKY and SD rats. Behaviorally inhibited WKY rats acquired lever-press avoidance responses faster and to a higher degree than non-inhibited SD controls. When switched to extinction training, WKY rats continue to respond to the tone when the shock is no longer presented early in extinction training, while the SD control rats reduce responding more rapidly. Figure adapted from Jiao et al. (2011a) with permission of the authors.
Figure 2
Figure 2
Acquisition and extinction of avoidance responses (hiding during the warning period) in the computer-based task. Individuals with PTSD symptoms (PTSS) exhibited higher levels of avoidance than individuals without PTSD symptoms (noPTSS), but did not differ in avoidance responses during extinction training. Figure adapted from Sheynin et al. (2017) with permission of the authors.
Figure 3
Figure 3
Acquisition of conditioned eyeblinks in WKY and SD rats with a tone CS and eyeshock US. Behaviorally inhibited WKY rats acquired conditioned eyeblinks faster and to a higher degree than non-inhibited SD controls. WKY rats also had slower extinction than SD controls to CS-alone trials (blocks 18–20 as indicated by the gray bar). Figure adapted from data from Beck et al. (2011) with permission of the authors.
Figure 4
Figure 4
Acquisition and extinction of conditioned eyeblinks in behaviorally inhibited and non-inhibited individuals with a tone CS and air puff US. Behaviorally inhibited individuals acquired conditioned eyeblinks faster and to a greater degree than non-inhibited individuals to a 50% CS-alone schedule of partial reinforcement. When switched to CS-alone extinction training, behaviorally inhibited individuals had slower extinction than non-inhibited individuals. Figure adapted from Allen et al. (2014) with permission of the authors.
Figure 5
Figure 5
Acquisition and extinction of conditioned eyeblinks with a tone CS and air puff US in military personnel with PTSD symptoms (PTSD+) and without PTSD symptoms (PTSD-). PTSD was associated with faster acquisition to a 50% CS-alone schedule of partial reinforcement and continued responding during extinction (tone alone) training. Figure adapted from Behavioural Brain Research, 339, Handy, J.D., Avcu, P., Ko, N., Ortiz, A., Doria, M.J., and Servatius, R.J. Facilitated acquisition of the classically conditioned eyeblink response in active duty military expressing posttraumatic stress disorder symptoms. 106-113, (2017) with permission of Elsevier.
Figure 6
Figure 6
The learning diathesis model of PTSD. Inhibited temperaments interact with changes in avoidance and associative learning leading to increased PTSD vulnerability. This model is supported by the avoidance learning and eyeblink conditioning studies reviewed from the rodent and human literature.

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References

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