RESEARCH ARTICLE


Exploring the Neurocircuitry Underpinning Predictability of Threat in Soldiers with PTSD Compared to Deployment Exposed Controls



Michael N. Dretsch*, a, b, Kimberly H. Woodc, Thomas A. Danield, f, Jeffrey S. Katzd, e, Gopikrishna Deshpanded, e, Adam M. Goodmand, f, Muriah D. Wheelockc, Kayli B. Woodc, Thomas S. Denney Jr.d, e, Stephanie Traynhama, David C. Knightc
a U.S. Army Aeromedical Research Laboratory, Fort Rucker, AL, USA
b Human Dimension Division, HQ TRADOC, 950 Jefferson Ave, Fort Eustis, VA 23604, USA
c Department of Psychology, University of Alabama at Birmingham, AL, USA
d Department of Psychology, Auburn University, Auburn, AL, USA
e AU MRI Research Center, Department of Electrical and Computer Engineering, Auburn University, Auburn, AL, USA
f Oak Ridge Institute for Science and Education, Oak Ridge, TN, USA


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© Dretsch et al.; Licensee Bentham Open.

open-access license: This is an open access article licensed under the terms of the Creative Commons Attribution-Non-Commercial 4.0 International Public License (CC BY-NC 4.0) (https://creativecommons.org/licenses/by-nc/4.0/legalcode), which permits unrestricted, non-commercial use, distribution and reproduction in any medium, provided the work is properly cited.

* Address correspondence to this author at the Human Dimension Division, HQ TRADOC, 950 Jefferson Ave, Fort Eustis, VA 23604, USA; Tel: 360.359.5950; Fax: 757.501.6419; E-mails: Michael.n.dretsch.mil@mail.mil, dretschphd@gmail.com


Abstract

Background:

Prior work examining emotional dysregulation observed in posttraumatic stress disorder (PTSD) has primarily been limited to fear-learning processes specific to anticipation, habituation, and extinction of threat. In contrast, the response to threat itself has not been systematically evaluated.

Objective:

To explore potential disruption in fear conditioning neurocircuitry in service members with PTSD, specifically in response to predictable versus unpredictable threats.

Method:

In the current study, active-duty U.S. Army soldiers with (PTSD group; n = 38) and without PTSD (deployment-exposed controls; DEC; n = 40), participated in a fear-conditioning study in which threat predictability was manipulated by presenting an aversive unconditioned stimulus (UCS) that was either preceded by a conditioned stimulus (i.e., predictable) or UCS alone (i.e., unpredictable). Threat expectation, skin conductance response (SCR), and functional magnetic resonance imaging (fMRI) signal to predictable and unpredictable threats (i.e., UCS) were assessed.

Results:

Both groups showed greater threat expectancy and diminished threat-elicited SCRs to predictable compared to unpredictable threat. Significant group differences were observed within the amygdala, hippocampus, insula, and superior and middle temporal gyri. Contrary to our predictions, the PTSD group showed a diminished threat-related response within each of these brain regions during predictable compared to unpredictable threat, whereas the DEC group showed increased activation.

Conclusion:

Although, the PTSD group showed greater threat-related diminution, hypersensitivity to unpredictable threat cannot be ruled out. Furthermore, pre-trauma, trait-like factors may have contributed to group differences in activation of the neurocircuitry underpinning fear conditioning.

Keywords: Amygdala, Fear-conditioning, Hippocampus, Insula, Military, Neuroimaging, PTSD.