Walter Rudolf Hess

Walter Rudolf Hess (1881-1973), Swiss physiologist and Nobel Prize winner whose experiments demonstrated how specific regions deep within the brain—and especially an area known as the hypothalamus—control involuntary bodily processes such as blood pressure and heart rate. Hess was awarded the 1949 Nobel Prize in physiology or medicine, which he shared with the Portuguese neurosurgeon António Egas Moniz, who also made groundbreaking studies of the brain.

Born in Frauenfeld, Switzerland, Hess studied medicine at the University of Lausanne, receiving his medical degree in 1906 from the University of Zürich. After building a successful practice as an ophthalmologist, Hess decided to pursue physiological research. In 1917 he accepted a position at the University of Zürich's Physiology Institute, where he spent the rest of his career until his retirement in 1951.

For nearly a decade, Hess studied the circulatory system, examining the regulation of the heart rate and blood pressure. In 1925, however, he decided to make a closer examination of how these functions are controlled by the autonomic, or involuntary, nervous system. Specifically, he examined an area deep in the brain known as the diencephalon, or interbrain. A key problem was the difficulty of reaching tissue so far inside the brain without damaging other, surrounding areas. Using great technical skill, Hess was able to place small electrodes through holes cut into the skulls of laboratory cats. Choosing specific sites in the interbrain, Hess placed electrodes and carefully secured them, so that the cats could move around relatively freely without being placed under anesthetic. Hess could then monitor their reactions when he stimulated these regions by sending weak electrical current through the electrodes.

Making careful observations and filmed records of his experiments, Hess built a detailed picture of how specific regions in the interbrain affect involuntary internal processes. The hypothalamus, in particular—an area located at the base of the brain—emerged as a key control center for blood pressure, respiration, body temperature, and other functions. Such responses as hunger, fear, and anger also seemed to center in the hypothalamus. In general, by his meticulous observations of how the regions in the brain influence specific bodily processes, Hess did much to provide a more exact, integrated understanding of brain and nervous-system function. Having worked for nearly a quarter of a century in relative isolation, Hess presented his considerable body of findings to the world in 1948.

After his retirement from the Physiology Institute in 1951, Hess continued his research on the function of the interbrain. He also helped to establish an institute for brain research.