Target variability and stability of neuroimaging-guided transcranial magnetic stimulation of the amygdala circuitry for posttraumatic stress disorder

Background: Transcranial magnetic stimulation (TMS) is a non-invasive neuromodulation therapy that is applied across psychiatric conditions to modulate specific neural circuits and improve clinical symptoms. While functional magnetic resonance imaging (fMRI)-guided personalized TMS targets are increasingly used, there are critical unresolved methodological, neurobiological, and clinical questions. Addressing topographic variability, stability, and associations with clinical outcomes is essential for advancing clinical development and scalable precision neuromodulation. Methods: A precision neurocircuitry-based fMRI-guided TMS approach was developed to treat disorders of the amygdala. In a randomized clinical trial for posttraumatic stress disorder (PTSD; n=50), topographic variability and stability of patient-specific right dorsolateral prefrontal cortex (rDLPFC) targets with the strongest functional connectivity to the right amygdala were analyzed. Results: There was significant target variability between participants and between targeting methods, but target stability was observed after engaging the amygdala circuitry with behavioral threat-related tasks. Target topography did not change after 20 sessions of sham TMS. However, after active TMS (1Hz, 36,000 pulses) target topography was significantly different. A larger change in the medial-anterior direction correlated with greater PTSD symptom improvement. Conclusions: Target variability and stability for fMRI-guided TMS of the amygdala circuitry is demonstrated, supporting the use of patient-specific targeting strategies for TMS. A clinical change in PTSD symptoms was associated with greater change in target topography, which suggests neuroplastic adaptations in the targeted networks and a possible treatment-dependent shift towards more medial prefrontal control over amygdala regulation. These findings are important for fMRI-guided precision neuromodulation therapy development, particularly for the amygdala circuitry.