Neuro-Cardiac-Guided Transcranial Magnetic Stimulation: a Method to Probe the Depression Network. Replication and Dose-response

Autonomic regulation is disturbed in patients with major depressive disorder (MDD), indicated by a higher heart rate (HR) and lower heart rate variability (HRV). Moreover, the heart seems to be functionally connected via the vagus nerve (VN) to other brain structures that are dysregulated in depression, such as the subgenual anterior cingulate cortex (sgACC), and the dorsolateral prefrontal cortex (DLPFC), suggesting dysregulated network function in MDD. In line with this network dysregulation hypothesis of MDD, optimal transcranial magnetic stimulation (TMS) sites are currently thought to be those that show functional connectivity to the sgACC such as the DLPFC and multiple studies have shown that stimulation of the DLPFC, sgACC and nervus vagus decreased heart rate, suggestive of parasymphatetic action. It is hypothesized that this influence on parasympathetic activity can be used as a functional outcome measure reflecting adequate targeting of the DLPFC-sgACC network, similar to the motor evoked potential (MEP) as functional key measure for primary motor cortex stimulation. Recently, a pilot study was conducted, proposing a new functional neuronavigation method for localizing the frontal area representation of DLPFC-sgACC connectivity using HR, called: Neuro-Cardiac-Guided TMS (NCG-TMS), which is being replicated in the current study. .