Reliability of brain localization using task-based fMRI for late-life depression with suicidal risk

Late-life depression (LLD) is a heterogeneous mental disorder with a high risk of suicide, often linked to abnormalities in brain networks, particularly the prefrontal cortex. While transcranial magnetic stimulation targeting the dorsal and ventral lateral prefrontal cortex (DLPFC and VLPFC) has shown promise, its treatment efficacy may be compromised by the imprecise group-level standard methods. Although a personalized localization approach using fMRI is available, no study has yet systematically evaluated its reliability in LLD. This study evaluated the reliability of functional magnetic resonance imaging (fMRI) for targeting DLPFC and VLPFC using numerical Stroop and face/shape matching tasks in LLD patients with varying degrees of suicidality, the disorder's most devastating consequence. A total of 103 LLD patients, including 42 with non-suicidal risk (NS), 37 with suicidal ideation or plans (IP), and 24 with past suicide attempts (SA), underwent task-based fMRI. We performed both voxel-wise statistical analyses and the success rate of DLFPC/VLPFC localization in each subgroup by detecting significant brain activity within predefined masks. The numerical Stroop task reliably localized the bilateral DLPFC in all subgroups and the VLPFC in two-thirds. Success rates for localizing DLPFC were 98 % (41 out of 42 NS), 100 % (IP), and 100 % (SA), while VLPFC localization rates were 95 %, 97 %, and 88 %, respectively. Conversely, the face/shape matching task localized bilateral DLPFC in two-thirds and failed to detect the VLPFC in any subgroup. These findings underscore the potential of task-based fMRI, particularly the numerical Stroop task, as a reliable method for personalized targeting in LLD patients with different suicidality degrees.