Exploring the relationship between synaptic density marker SV2A PET imaging and acute neuroplastic potential with interleaved TMS-fMRI in treatment resistant depression
Depression is a common mental health condition that affects millions of Canadians. While there are treatment options available, some patients do not respond to conventional antidepressants and receive direct-to-brain stimulation therapy with repetitive transcranial magnetic stimulation (rTMS). rTMS is a non-invasive treatment that uses magnetic pulses to stimulate specific areas of the brain that are dysfunctional in depression. Unfortunately, rTMS is ineffective in one third of patients, and it is unclear whether this is due to a lack of connections among brain cells (synapses) in depression. This study will explore the relationship between the
brain’s synaptic density and the effectiveness of rTMS in stimulating brain circuits altered in depression.
Functional magnetic resonance imaging (fMRI) will be used to probe brain activity during TMS stimulation, while a novel imaging technique called positron emission tomography (PET) will measure the brain’s synaptic density, thought to play a role in depression. The connection between synaptic density and the brain’s acute response to TMS will be compared before patients receive rTMS therapy. Additionally, the study will investigate if measures of brain function are associated with changes in synaptic density after rTMS treatment.
Overall, this study aims to improve our understanding of how rTMS works to treat depression. If successful, these findings would support the idea that impaired synaptic connectivity is associated with response to brain stimulation and open new therapeutic pathways for enhancing rTMS outcomes in persons with low synaptic density.
Sean Nestor , University of Toronto