You need to talk to the patient safety folks in your lab. University Labs and Hospitals I have worked in typically had stringent safety protocols which were especially rigorous when it came to experimentation on healthy humans...
AFAICR, we were not allowed to have a DC path between any AC-line-powered equipment such as your Function Gen or Scope and the subject, even if the equipment was powered via an isolation transformer. About 35 years ago I built a stimulator used to stimulate the occipital cortex of human subjects; it was battery powered and optically-isolated. Perhaps, since your application is less invasive, your human-experimentation committee might agree that the isolation transformer is sufficient.