Research
Hess used brain stimulation that were developed in the late 1920s, using electrodes to stimulate the brain at well-defined anatomical regions. This allowed him to map regions of the brain to specific physiological responses. He developed a special technique he called "interrupted direct-current (DC) stimulation" which used stimuli of long duration (typically 12.5 or 25 ms) with ramp-like upward and downward slopes. Also, the stimuli were rather weak (around 0.5–1.5 V) and of low frequency (2–12 Hz, usually 8 Hz) and he used very fine electrodes with a diameter of 0.25 mm.
By stimulating the hypothalamus, he could induce behaviors from excitement to apathy; depending on the region of stimulation. He found that he could induce different types of responses when stimulating the anterior (lateral) hypothalamus compared to stimulating the posterior ventromedial hypothalamus. When stimulating the anterior part, he could induce fall of blood pressure, slowing of respiration and responses such as hunger, thirst, micturition (urination) and defecation. On the other hand, stimulation of the posterior part led to extreme excitement and defense-like behavior.
Hess also found that he could induce sleep in cats - a finding that was highly controversial at the time but later confirmed by other researches, including his son Rudolf Max Hess.
Read more about this topic: Walter Rudolf Hess
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