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Modeling the Effects of Post-Traumatic Stress on Hippocampal Volume

Authors
Ms. Briana Marie Smith
University of Washington ~ Psychology
Madison Chiu
University of Washington, United States of America
Ms. Yuxue Yang
University of Washington Seattle ~ Psychology
Dr. Catherine Sibert
University of Washington ~ Department of Psychology
Prof. Andrea Stocco
University of Washington ~ University of Washington
Abstract

Post-Traumatic Stress Disorder (PTSD) is a psychiatric disorder often characterized by the unwanted re-experiencing of a traumatic event through nightmares, flashbacks, and/or intrusive memories. This paper presents a neurocomputational model using the ACT-R cognitive architecture that simulates intrusive memory retrieval following a potentially traumatic event (PTE) and derives predictions about hippocampus volume observed in PTSD. Memory intrusions were captured in the ACT-R Bayesian framework by weighting the posterior probability with an emotional intensity term I to capture the degree to which an event was perceived as dangerous or traumatic. It is hypothesized that (1) Increasing the intensity I of a PTE will increase the odds of memory intrusions; and (2) Increased intrusions will result in a concurrent decrease in hippocampal size. A series of simulations were run and it was found that I had a significant effect on the probability of experiencing traumatic memory intrusions following a PTE. The model also found that I was a significant predictor of hippocampal volume reduction, where the mean and range of simulated volume loss match results of existing meta-analysis. The authors believe that this is the first model to both describe traumatic memory retrieval and provide a mechanistic account of changes in hippocampal volume, capturing one plausible link between PTSD and hippocampus size.

Discussion
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Questions Last updated 2 months ago

Hi, thanks for your presentation, very nice work! I found the implementation and explanation of the model very clear. I have two questions: 1. You increased the probability of recalling the traumatic memory by including an intensity value to the activation. I'm wondering if there could also be a change in the recall probability due to changes in...

Maarten van der Velde 0 comments

very interesting stuff! I was wondering whether you also have empirical data to support this idea that hippocampal volume decreases due to PTSD. And if so: could it be that those with a smaller hippocampus are more predisposed to PTSD? In addition, I was wondering why you chose a multiplicative effect of traumatic memories rather than, say, an add...

Marieke Van Vugt 0 comments
Thank you! Questions Last updated 3 months ago

Hi Briana, Many thanks for your presentation! It was very clear, and the project is very interesting. I have a few follow-up questions for you: 1) I understand why you would want to add a constant bias I(m) to encode the emotional intensity of specific memories (which you added as log(I(m)) in the computation of the total activation). However, I a...

Mr. Pierre Gianferrara 0 comments
Thank you! Last updated 3 months ago

Thank you for viewing my presentation of "Modeling the Effects of Post-Traumatic Stress on Hippocampal Volume." Please comment with any questions, ideas, and suggestions you may have about this project--all input is welcome. I look forward to hearing from you, Briana Smith

Ms. Briana Marie Smith 0 comments