Walter Hess and his Mapping of the Brain

Walter Hess (1881 - 1971)

Walter Hess (1881 – 1971)

On March 17, 1881Swiss physiologist Walter Rudolf Hess was born. Hess shared the Nobel Prize in Physiology or Medicine in 1949 with Antonio Egas Moniz for his discovery of the functional organization of the interbrain as a coordinator of the activities of the internal organs.

In his early years, Walter Hess was supported by his father who was a physics teacher and allowed him to perform experiments in his laboratory. In 1899, Hess began to study medicine in Lausanne and later also in Berlin, Kiel and Zurich. After seven years, Hess earned his medical degree and began his training as a surgeon in Münsterlingen under Conrad Brunner. In 1912, when Walter Hess was already a family father with a position in a respected practice, he returned to the position of assistant, in physiology.

During the First World War Hess spent a year at the Physiological Institute of the University of Bonn under the physiologist Max Verworn. Walter Hess was appointed Director of the Physiological Institute at Zurich, along with teaching responsibilities. During the 1920s, Hess started using electrodes to stimulate the brain at well-defined anatomical regions. This technique allowed him to map regions of the brain to physiological responses. Walter Hess developed the interrupted direct-current stimulation using rather weak and low frequency stimuli for long duration. Hess found out that depending on the region of the induced stimulation, he was able to evoke behaviors from excitement to apathy. Hess was hence able to differentiate between responses when stimulating the anterior (lateral) hypothalamus or the posterior ventromedial hypothalamus. For instance, Hess could influence the fall of blood pressure, hunger, thirst, as well as defecation or excitement.

In his experiments, using electrodes in his brain, he succeeded in triggering emotions in cats. Similar experiments were later followed by Erich von Holst with chickens and José Manuel Rodriguez Delgado (Yale University) with apes and humans. In 1949 he and António Caetano de Abreu Freire Egas Moniz [4] jointly received the Nobel Prize for Physiology or Medicine: Hess for “discovering the functional organization of the interbrain for the coordination of the activity of internal organs“, and Moniz for “discovering the therapeutic value of prefrontal leukotomy in certain psychoses”.

Hess also dealt scientifically with the organization of motor skills, as a result of which he developed modern concepts of extrapyramidal motor skills. Until old age, he also studied the interaction between the vegetative nervous system and the psyche.

Walter Hess retired in 1951 and moved to Ascona in 1967. In 1973, Walter Rudolf Hess died in Locarno, Switzerland.

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