Hess, Walter Rudolf

(1881–1973) Swiss neurophysiologist: showed that localized areas in the brain control specific functions.

Hess studied medicine at five universities in Switzerland and Germany and became a specialist ophthalmologist, but gave up this career to work in physiology and from 1917–51 headed physiology in the university of Zürich. The precision surgery he had learned as an ophthalmologist was to prove useful; in the 1920s he began his study of the autonomic nervous system, which controls involuntary functions such as breathing, blood pressure, temperature and digestion.

It was already known roughly which parts of the brain are involved in this control; but Hess made this knowledge much more precise. He used cats into which, under anaesthetic, a fine insulated wire with a bare end was inserted so that the end was located at a defined point in the midbrain. When the animal was again conscious, a very small current was passed into the wire. Hess found that by this stimulation of small groups of cells in the midbrain he could induce a variety of reactions, including sleep, rage, evacuation and changes in blood pressure and respiration. Similarly, in the hypothalamus he located centres that appeared to control other parts of the sympathetic and parasympathetic components of the autonomic system. This influential work led to detailed mapping of the brain and began to relate physiology to psychiatry. He shared a Nobel Prize in 1949.