isolated brain isolated brain an isolated brain is a brain kept alive in vitro, either by perfusion or by a blood substitute, often an oxygenated solution of various salts, or by submerging the brain in oxygenated artificial cerebrospinal fluid (csf). it is the biological counterpart of brain in a vat. a related concept, attaching the brain or head to the circulatory system of another organism, is called a head transplant. an isolated brain, however, is more typically attached to an artificial perfusion device rather than a biological body.