A mechanistic trial of the neurobiology of extinction learning and intraparietal sulcus stimulation: Protocol

Post-traumatic stress disorder (PTSD) links to impaired extinction learning post-trauma. While treatments like prolonged exposure therapy improve this learning, they benefit only 40-60 % of patients. Optimal arousal supports extinction learning, but excessive arousal can hinder it. The intraparietal sulcus (IPS) is involved in arousal regulation but has not yet been targeted using continuous theta burst stimulation (cTBS) in PTSD. This study is the first to explore the effect of IPS cTBS on extinction learning in PTSD. This study aims to 1) evaluate the impact of IPS cTBS on anxiety potentiated startle (APS) among patients with PTSD compared to sham IPS cTBS, 2) examine whether IPS cTBS improves extinction learning relative to neutral learning, and 3) identify the ideal dose of cTBS. Adults with PTSD will participate in six visits, involving clinical assessments, functional MRI (fMRI), and IPS cTBS. Participants will undergo diagnostic interviews, generate trauma and neutral scripts, and complete script-driven imagery tasks. They will receive active or sham cTBS (counterbalanced) paired with trauma or neutral scripts during separate visits. Follow-up assessments occur at 24 h and 30 days post-intervention. IRB approval and preliminary preparations began in January 2024. Recruitment started in April 2024 and is projected to conclude by April 2028. Ethical procedures are approved by the University of Pennsylvania IRB (Protocol Number: 849571). This will be the first study to evaluate the synergistic effects of extinction training with IPS cTBS in individuals with PTSD. Our findings will strengthen the neurobiological basis of augmenting extinction training with IPS cTBS.