Neurological Reactivity to Personalized Odors and Sounds in Combat-related Posttraumatic Stress Disorder

Functional near-infrared spectroscopy (fNIRS) is a neurophysiological procedure that offers immense clinical utility due to its cost effectiveness, ease of use, and mobile application. Using fNIRS to measure neurological reactions to personalized trauma-related cues might strengthen diagnostic screening, tailor treatment planning, and improve detection of remission among individuals with posttraumatic stress disorder (PTSD). Odors elicit strong emotional responses but remain underutilized in clinical research. This fNIRS study examined whether personalizing combat-related odors and sounds to have a higher or lower match to distressing combat experiences increased the observed neurological effect among combat veterans with and without combat-related PTSD. This study gathered data from 58 male, right-handed combat veterans of Iraq or Afghanistan, ages 26 to 68, recruited from the community. The results indicated a significant increase in activation at the left ventral lateral prefrontal cortex (VLPFC) following an interaction between higher PTSD severity and higher match ratings for the combat-related odors (R2 = .20, p = .003; f2 = .25). Furthermore, the left VLPFC showed a significant increase in activation following an interaction between having a PTSD diagnosis and higher match ratings for the combat-related odors (R2 = .25, p = .005; f2 = .33). The findings for the combat-related sounds were less clear. The left VLPFC is associated with facilitating regulation of memory and emotional processes. Overall, the presentation of odors with higher similarity to distressing combat experiences altered the neurological response of the prefrontal cortex and may contribute to better understanding of the neurophysiological mechanisms of combat-related PTSD