Abstract: Beams of coherent microwaves or other frequencies of highly directional electromagnetic radiation are passed through the living human body to detect and provide a quantitative analysis of functional activity in the central nervous system and/or in muscle tissue such as that of the heart. Organs to be analyzed are situated in the space of an electrostatic field of oscillating intensity. The directional beam is passed through a body organ situated in this way. The method is of use in detecting degenerative subcortical disease in the brain (e.g., Sulphatide Lipidosis), tissue damage to nerve fibers due to toxic chemicals, and other types of tissue-based functional abnormality. Functional condition of brain and heart generally can be readily analyzed without exposure to ionizing radiation.