title: Prefrontal responses to digit span memory phases in patients with post-traumatic stress disorder (PTSD): a functional near infrared spectroscopy study.
abstract: Neuroimaging studies of post-traumatic stress disorder (PTSD)-related memory impairments have consistently implicated abnormal activities in the frontal and parietal lobes. However, most studies have used block designs and could not dissociate the multiple phases of working memory. In this study, the involvement of the prefrontal cortex in working memory phases was assessed among veterans with PTSD and age-/gender-matched healthy controls. Multichannel functional near infrared spectroscopy (fNIRS) was utilized to measure prefrontal cortex hemodynamic activations during memory of neutral (i.e., not trauma-related) forward and backward digit span tasks. An event-related experimental design was utilized to dissociate the different phases (i.e., encoding, maintenance and retrieval) of working memory. The healthy controls showed robust hemodynamic activations during the encoding and retrieval processes. In contrast, the veterans with PTSD were found to have activations during the encoding process, but followed by distinct deactivations during the retrieval process. The PTSD participants, but not the controls, appeared to suppress prefrontal activity during memory retrieval. This deactivation was more pronounced in the right dorsolateral prefrontal cortex during the retrieval phase. These deactivations in PTSD patients might implicate an active inhibition of dorsolateral prefrontal neural activity during retrieval of working memory.
authors.affiliation: Department of Bioengineering, The University of Texas at Arlington, Arlington, USA.
authors.forename: Fenghua
authors.initials: F
authors.lastname: Tian
authors.affiliation: Department of Bioengineering, The University of Texas at Arlington, Arlington, USA.
authors.forename: Amarnath
authors.initials: A
authors.lastname: Yennu
authors.affiliation: School of Social Work, The University of Texas at Arlington, Arlington, USA.
authors.forename: Alexa
authors.initials: A
authors.lastname: Smith-Osborne
authors.affiliation: Department of Psychology, The University of Texas at Austin, Austin, USA.
authors.forename: F
authors.initials: F
authors.lastname: Gonzalez-Lima
authors.affiliation: VA North Texas Health Care System, Dallas, TX, USA ; Department of Psychiatry, The University of Texas Southwestern Medical Center, Dallas, TX, USA ; Department of Surgery, The University of Texas Southwestern Medical Center, Dallas, TX, USA.
authors.forename: Carol S
authors.initials: CS
authors.lastname: North
authors.affiliation: Department of Bioengineering, The University of Texas at Arlington, Arlington, USA.
authors.forename: Hanli
authors.initials: H
authors.lastname: Liu
mesh_terms: D000328:Adult; D000704:Analysis of Variance; D001931:Brain Mapping; D016022:Case-Control Studies; D006439:Hemodynamics / Q000502:physiology*; D006454:Hemoglobins / Q000378:metabolism; D006801:Humans; D007091:Image Processing, Computer-Assisted; D008279:Magnetic Resonance Imaging; D008297:Male; D008433:Mathematics; D008569:Memory Disorders / Q000209:etiology*; D008570:Memory, Short-Term / Q000502:physiology; D008875:Middle Aged; D017397:Prefrontal Cortex / Q000378:metabolism*; D019265:Spectroscopy, Near-Infrared; D013313:Stress Disorders, Post-Traumatic / Q000150:complications* / Q000473:pathology*; D055815:Young Adult
chemical_list: D006454:Hemoglobins
keywords: Digit span; Functional near infrared spectroscopy (fNIRS); Hemispheric emotional valence (HEV); Post-traumatic stress disorder (PTSD); Topography; Working memory