Neural correlates of attention bias in posttraumatic stress disorder

Patients suffering from posttraumatic stress disorder (PTSD) exhibit hyper arousal symptoms and attention problems which were frequently investigated using the P3 event-related potentials (ERPs). Our study aimed at providing more precise knowledge of the functional significance of the P3 alteration seen in PTSD by revealing its spatio-temporal dynamics.

Fifteen PTSD patients and fifteen healthy trauma-exposed controls participated in a three-tone "oddball" task while their brain activity was recorded by magnetoencephalography (MEG). They were asked to detect rare target tones and ignore standard tones and infrequent threatening distractors. An adaptive spatial-filter method (SAM beamformer) was applied for source estimation.

Compared with controls, PTSD patients had more incorrect responses to standard stimuli. On the brain level, PTSD patients showed hyperactivity in the dorsolateral prefrontal cortex and anterior cingulate cortex in response to standard sounds, decreased activity in those regions in response to threatening distractors, and decreased orbitofrontal activity in response to target stimuli.

Increased frontal activation in response to standard, neutral, stimuli may reflect greater resource allocation dedicated to cognitive control mechanisms during routine functioning in PTSD. Decreased frontal activation in response to rare stimuli may reflect subsequently reduced residual resources for detecting rare stimuli and for emotion regulation. This may explain the hypervigilance and attention problems commonly reported by patients.

The current findings contribute to a better understanding of the mechanisms underlying the attention deficiency in PTSD, and highlight altered activity in specific frontal regions as potential biomarkers.