Functional abnormality of the prefrontal cortex in posttraumatic stress disorder: Psychophysiology and treatment studies assessed by near-infrared spectroscopy

Abstract

A growing number of functional neuroimaging studies on posttraumatic stress disorder(PTSD) have described the abnormal response of amygdala and prefrontalcortex to traumatic stimuli (Bremner et al, 1999; Shin et al, 2001; 2004; Lanius2001; Zubieta et al 1999; Matsuo et al. 2003a). Furthermore, it has been reportedthat these abnormalities respond to treatment (Levin et al. 1999; Seedat et al. 2004;Carey et al. 2004). A large number of the studies on the prefrontal cortex in PTSDhave shown diminished activation of this region in response to trauma-related stimuli(Bremner et al. 1999; Shin et al. 2001, 2004; Lanius et al. 2001). In contrast,several studies have shown greater activation of the prefrontal cortex (Zubieta et al.1999; Matsuo et al. 2003a). In a positron emission tomography (PET) study (Bremneret al. 1999), combat veterans with PTSD showed diminished activation of themedial prefrontal cortex in response to trauma-related stimuli. Moreover, the decreasedblood flow in the medial prefrontal cortex was found to be negatively correlatedwith increased blood flow in the amygdala in response to the traumatic stimuliand positively correlated with the severity of the symptoms. This suggested thatinsufficient suppression of the medial prefrontal cortex in response to the overactivationof the amygdala could be considered as a pathophysiological model of PTSD(Shin et al. 2004). Functional magnetic resonance imaging (fMRI) studies haveshown similar findings (Lanius et al. 2001; Shin et al. 2001). Using single photonemission computed tomography (SPECT), Zubieta et al. (1999) examined regionalcerebral blood flow (rCBF) responses to a combat stress-related auditory stimulusin Vietnam war veterans with PTSD and found that PTSD patients showed a significantincrease in blood flow to the medial prefrontal cortex, which correlated at trend levels with psychophysical measures of stress response. In summary, abnormal activationof some parts of the prefrontal cortex might possibly be involved in thepathophysiology of PTSD.