J Psychiatry Neurosci 2010; 35(5): 258-266
Judith K. Daniels, PhD; Alexander C. McFarlane, MD; Robyn L. Bluhm, PhD; Kathryn A. Moores, PhD; C. Richard Clark, PhD; Marnie E. Shaw, PhD;
Peter C. Williamson, MD; Maria Densmore, BSc; Ruth A. Lanius, MD, PhD
Daniels, Williamson, Densmore, Lanius — Department of Psychiatry, Schulich School of Medicine and Dentistry, The University of Western Ontario, London, Ont.; Daniels — University Medical Center Hamburg-Eppendorf, University of Hamburg, Germany; McFarlane — The Centre of Military and Veterans’ Health and Department of Psychiatry, University of Adelaide, Adelaide, Australia; Bluhm — Department of Philosophy and Religious Studies, Old Dominion University, Norfolk, Va.; Moores, Clark — Cognitive Neuroscience Laboratory, School of Psychology, Flinders University, Adelaide, Australia; Shaw — Brain Research Institute, Florey Neuroscience Institutes, Melbourne, Australia
Background: Working memory processing and resting-state connectivity in the default mode network are altered in patients with posttraumatic stress disorder (PTSD). Because the ability to effortlessly switch between concentration on a task and an idling state during rest is implicated in both these alterations, we undertook a functional magnetic resonance imaging study with a block design to analyze task-induced modulations in connectivity.
Methods: We performed a working memory task and psychophysiologic interaction analyses with the posterior cingulate cortex and the medial prefrontal cortex as seed regions during fixation in 12 patients with severe, chronic PTSD and 12 healthy controls.
Results: During the working memory task, the control group showed significantly stronger connectivity with areas implicated in the salience and executive networks, including the right inferior frontal gyrus and the right inferior parietal lobule. The PTSD group showed stronger connectivity with areas implicated in the default mode network, namely enhanced connectivity between the posterior cingulate cortex and the right superior frontal gyrus and between the medial prefrontal cortex and the left parahippocampal gyrus.
Limitations: Because we were studying alterations in patients with severe, chronic PTSD, we could not exclude patients taking medication. The small sample size may have limited the power of our analyses. To avoid multiple testing in a small sample, we only used 2 seed regions for our analyses.
Conclusions: The different patterns of connectivity imply significant group differences with task-induced switches (i.e., engaging and disengaging the default mode network and the central-executive network).
Submitted Dec. 2, 2009; Revised Feb. 11, 2010; Accepted Feb. 11, 2010.
Acknowledgments: This study was supported by the Australia Research Council (grant no. A00105227) and the National Health and Medical Research Council of Australia (grant no. 981270.
Competing interests: None declared for Drs. Daniels, Shaw,
Williamson and Lanius and Ms. Densmore. Dr. McFarlane and his institute have received National Health and Medical Research Council (NHMRC) program and project grants. Dr. Bluhm has received payment for writing and reviewing the a manuscript from The University of Western Ontario as part of her postdoctoral fellowship. Drs. Moores’s and Clark’s institutions have received NHMRC grants.
Contributors: Drs. Daniels, McFarlane, Bluhm, Moores and Lanius designed the study. Drs. McFarlane, Moores and Clark and Ms. Densmore acquired the data, which all authors analyzed. Drs. Daniels, McFarlane, Bluhm and Lanius wrote the article. All authors reviewed the article and approved its publication.
Correspondence to: Dr. R.A. Lanius, University Campus, London Health Sciences Centre, 339 Windermere Rd., London ON N6A 5A5; fax 519 663-3935; firstname.lastname@example.org