Imaging Brain Fluids During Breathing

Neuroimaging the Impact of Respiration and Respiratory-gated Neuromodulation on Human Glymphatic Physiology

This study will perform magnetic resonance imaging (MRI) measurements of hemodynamics and cerebrospinal fluid flow across breathing tasks and during breath-locked neuromodulation.

Cerebrospinal fluid (CSF) flow is essential for brain health, as it clears waste products from the brain. This study will investigate how breathing affects the flow of CSF around the brain. The investigators will perform high resolution magnetic resonance imaging (MRI) scans in participants who are breathing in specific patterns or performing simple tasks and test the effects on CSF flow. Participants will complete an imaging study visit in which the investigators will image their brain activity while they perform simple tasks, including paced breathing tasks. The participants will be split into two arms: (1) paced breathing (25 participants low resolution, 15 participants high resolution), (2) transcutaneous vagal nerve stimulation (25 participants low resolution, 15 participants high resolution). The MRI scans will take place in the 7 Tesla MRI scanner at Massachusetts General Hospital.

Inclusion Criteria:

• Adult age 18-70 years

Exclusion Criteria:

• No ferrous metal implanted in head or body
• No history of major head trauma
• No neurological or psychiatric disorder
• Not using medication that affects brain function
• No implanted electronic devices (e.g. pacemaker)
• No implant that poses an MR contraindication
• Not pregnant, suspect they are pregnant, or seeking to become pregnant
• Not claustrophobic
• No piercings or jewelry that cannot be removed
• Does not weigh more than 250 pounds
• Normal or contact-corrected normal vision

Exclusion for transcutaneous vagus nerve stimulation (tVNS) arm:

• Conditions of skin or anatomy that affect left auricle or forehead skin and could impact placement of electrodes for tVNS or forehead stimulation
• Diagnosis of significant cardiovascular or cerebrovascular disease [e.g. congestive heart failure, stroke, cardiac conduction disorders (including: bundle branch block, heart block, long Q-T syndrome), history of asystole or non-sustained ventricular tachycardia.
• Bradycardia (defined as resting heart rate <50 bpm)
• Hypotension defined as blood pressure <90/60 mmHg