Combining pleasant Olfactory and BRAin stimulations in treatment-resistant depression (COBRA): study protocol for a randomized controlled trial.

Background: Anhedonia, including social, physical, and less-known, olfactory, stands as a core symptom of major depressive disorder (MDD). At the neurobiological level, anhedonia has been associated with abnormal activity within the reward system, suggesting a key role for dopamine. Repetitive Transcranial Magnetic Stimulation (rTMS) has emerged as an innovative treatment for alleviating depressive symptoms.

Combining a Breath-Synchronized Olfactometer with Brain Simulation to Study the Impact of Odors on Corticospinal Excitability and Effective Connectivity.

It is widely accepted that olfactory stimulation elicits motor behaviors, such as approaching pleasant odorants and avoiding unpleasant ones, in animals and humans. Recently, studies using electroencephalography and transcranial magnetic stimulation (TMS) have demonstrated a strong link between processing in the olfactory system and activity in the motor cortex in humans. To better understand the interactions between the olfactory and the motor systems and to overcome some of the previous methodological limitations, we developed a new method combining an olfactometer that synchronizes the random order presentation of odorants with different hedonic values and the TMS (single- and dual-coil) triggering with nasal breathing phases.