Attenuated prefrontal and temporal neural activity during working memory as a potential biomarker of suicidal ideation in veterans with PTSD

Background: Suicide is a significant health concern among veterans, and suicidal ideation is a common and functionally debilitating condition that frequently precedes suicidal behavior. Characterizing neurobiological substrates associated with suicidal ideation in veterans may inform evaluation of risk for this population. Associations between suicidal ideation and functional abnormalities in prefrontal, temporal, and striatal regions supporting cognitive task performance have been documented in individuals with mood and psychotic disorders, suggesting a potential role for neurocognitive vulnerabilities in this condition. To date, however, relatively little research has explored neural correlates of suicidal ideation, particularly among individuals with posttraumatic stress disorder (PTSD).

Methods: Twenty three combat veterans diagnosed with PTSD completed an adapted Reading Span (Rspan) working memory task during functional magnetic resonance imaging (fMRI). Participants were classified based on presence of current SI. We evaluated differences between these groups on neural activation in response to interference-based working memory demands within the task. Primary analyses were conducted using a voxel-wise between-group t-test.

Results: Task-based activations were observed in regions including the cingulate, middle frontal, parietal, and occipital cortex, striatum, and cerebellum. Relative to individuals without SI, individuals with SI demonstrated less activation in a large region spanning the lateral prefrontal cortex and cingulate cortex, as well as the inferior temporal cortex, in response to interference demands.

Conclusions: Results are consistent with models proposing that prefrontal neural substrates involved in cognitive regulation are implicated in suicidal ideation. Involvement of temporal functioning may also exist based on current findings. Future research is needed to understand whether disturbances in prefrontal regulatory control reflect a specific profile subtype with distinct neural correlates, and how such neural patterns may be used to improve detection and treatment personalization.