A MEDICAL MICROELECTRODE HAS A FRONT END, A REAR END AND A DENSITY AT 20°C OF FROM 0.80 TO 1.15. THE ELECTRODE COMPRISES ANY OF: ELECTRICALLY CONDUCTIVE TUBIFORM LEAD COMPRISING OR CONSISTING OF A METAL AND/OR AN ELECTRICALLY CONDUCTIVE POLYMER, THE LEAD HAVING AN OUTER SURFACE AND A SEALED LUMEN； ELECTRICALLY CONDUCTIVE WIRE LEAD COMPRISING OR CONSISTING OF A METAL AND/OR AN ELECTRICALLY CONDUCTIVE POLYMER, THE LEAD HAVING A SURFACE AND A BUOYANT ELEMENT OF A DENSITY OF LESS THAN 1.0 ATTACHED TO THE SURFACE. (FIG. 1)
