Post-traumatic stress symptoms are associated with better performance on a delayed match-to-position task.

Meghan D Caulfield,Catherine E Myers

doi:10.7717/peerj.4701

Abstract

Many individuals with posttraumatic stress disorder (PTSD) report experiencing frequent intrusive memories of the original traumatic event (e.g., flashbacks). These memories can be triggered by situations or stimuli that reflect aspects of the trauma and may reflect basic processes in learning and memory, such as generalization. It is possible that, through increased generalization, non-threatening stimuli that once evoked normal memories become associated with traumatic memories. Previous research has reported increased generalization in PTSD, but the role of visual discrimination processes has not been examined. To investigate visual discrimination in PTSD, 143 participants (Veterans and civilians) self-assessed for symptom severity were grouped according to the presence of severe PTSD symptoms (PTSS) vs. few/no symptoms (noPTSS). Participants were given a visual match-to-sample pattern separation task that varied trials by spatial separation (Low, Medium, High) and temporal delays (5, 10, 20, 30 s). Unexpectedly, the PTSS group demonstrated better discrimination performance than the noPTSS group at the most difficult spatial trials (Low spatial separation). Further assessment of accuracy and reaction time using diffusion drift modeling indicated that the better performance by the PTSS group on the hardest trials was not explained by slower reaction times, but rather a faster accumulation of evidence during decision making in conjunction with a reduced threshold, indicating a tendency in the PTSS group to decide quickly rather than waiting for additional evidence to support the decision. This result supports the need for future studies examining the precise role of discrimination and generalization in PTSD, and how these cognitive processes might contribute to expression and maintenance of PTSD symptoms.

Highlights

When exposed to a traumatic event, some individuals develop posttraumatic stress disorder (PTSD), including re-experiencing symptoms such as frequent intrusive memories, believed to be triggered by situations that resemble aspects of the traumatic event (e.g., Elzinga & Bremner, 2002; Brewin & Holmes, 2003; How to cite this article Caulfield and Myers (2018), Post-traumatic stress symptoms are associated with better performance on a delayed match-to-position task
To determine if poor visual discrimination underlies increased generalization previously observed in Veterans with PTSD we used a visual match-to-sample pattern separation task
Given prior research documenting increased generalization in PTSD, it might be expected that the PTSD symptoms (PTSS) group would show correspondingly decreased discrimination, on the more difficult trials

Summary

Introduction

When exposed to a traumatic event, some individuals develop posttraumatic stress disorder (PTSD), including re-experiencing symptoms such as frequent intrusive memories (e.g., flashbacks), believed to be triggered by situations that resemble aspects of the traumatic event (e.g., Elzinga & Bremner, 2002; Brewin & Holmes, 2003; How to cite this article Caulfield and Myers (2018), Post-traumatic stress symptoms are associated with better performance on a delayed match-to-position task. Learning and memory processes such as generalization and discrimination may underlie re-experiencing symptoms in PTSD. Patients with PTSD may be impaired at discrimination, the ability to distinguish and respond differently to similar stimuli, and/or may show increased generalization, the ability to take what is learned about one stimulus and apply it to other. A consequence of increased generalization is that stimuli, which once evoked normal memories, become capable of evoking traumatic memories (e.g., Tryon, 1998; Van Meurs et al, 2014)

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