The Role of the Middle Temporal Gyrus in Suicide Risk

Over the last 20 years, suicide rates have steadily increased, and veterans, who are twice as likely to die by suicide than US civilians, are at increased risk. This risk is even higher for those with traumatic brain injury or psychiatric diagnoses such as PTSD and depression. Therefore, identifying veterans who have an increased risk for suicide is of urgent concern; however, there has been limited progress in identifying reliable predictors of suicide risk over the last 50 years. While suicide attempt history is one of the most reliable predictors of future suicide risk, little is known about the mechanisms that differentiate between those with a history of SA from those without. The PI has previously identified that the resting state functional connectivity of the right middle temporal gyrus (MTG) to the default mode network (a brain network involved in self-referential processing) significantly differentiated between veterans with and without a history of suicide attempt both before and after the reported suicide attempt. The MTG has been previously implicated in suicide-specific cognitions like self-death associations (i.e., self-referential thought) as assessed by the suicide implicit association test. It is also more generally involved in controlling multisensory integration of emotional stimuli, like emotional faces, music, and movies. However, it is unclear how the functions of the MTG may contribute to suicide risk. Taken together, the MTG potentially plays a critical role in suicide risk, but the nature of this role has yet to be determined. This proposal will seek to investigate the role of the MTG in those with a history of a suicide attempt. Specifically, this project will recruit a sample of veterans with a history of a suicide attempt (HoSA; n = 24) and a sample of veterans without a history of a suicide attempt (NHoSA; n = 24). Importantly, all participants in this study will have a current diagnosis of PTSD or depression, and we will assess current levels of suicidal ideation, PTSD, depression, and substance abuse symptoms to control and assess for potential differences between these two groups in psychiatric conditions that are often comorbid with suicide risk. We will measure brain activation of MTG during fMRI tasks that have previously implicated the MTG: emotional disengagement while watching emotional movies and the suicide implicit association test (SIAT). The aims of this study are to identify if brain activation of the MTG during these tasks differentiate between those with and without a history of a suicide attempt. Specifically, we hypothesize that the those with a history of a suicide attempt will show aberrant activation in the MTG during tasks that measure emotion disengagement and self-referential thought. This project will provide the PI with critical pilot data for a larger grant that will a.) investigate the reliability of these brain markers over time and b.) investigate modulating MTG activity as a potential treatment target to decrease suicide risk.