WordNet records no synonym and no antonym for biofeedback. It is the only member of its synset, which is common for technical, taxonomic and single-sense vocabulary — there is no other English word that means the same thing. The broader and narrower terms below are the useful relations in that case.
Counts are distinct word forms across every sense. A synonym that appears under three senses is counted once here and shown three times below, under each sense it belongs to.
a training program in which a person is given information about physiological processes (heart rate or blood pressure) that is not normally available with the goal of gaining conscious control of them
Synonyms, antonyms and the broader and narrower relations for biofeedback come from Princeton University’s WordNet. Full sources and licences.