Dr Werner P Koella, aged 91 years, passed away on 13 January 2008. After graduating from the University of Zurich in 1942, he started his career at the Clinic of Neurosurgery of the Zurich University Hospital. After 2 years of clinical activity, his interest in the functioning of the central nervous system led him to join the Institute of Physiology. Under the guidance of Professor WR Hess, Nobel laureate in medicine and physiology, he first directed his research efforts toward the experimental study of nystagmus and the role of the hypothalamus in fluid excretion. He made use of the technique of electrical brain stimulation in the unanesthetized cat and reported in 1952 together with K Akert and R Hess Jr on the sleep-inducing action of thalamic stimuli. In the following year, the same authors published the paper ‘Cortical and subcortical recordings in natural and artificially induced sleep in cats,’ which has been highly cited and marks the beginning of Koella's career in experimental sleep research. In 1951, he moved to the Department of Physiology of the University of Minnesota, where he joined the neurophysiology laboratory of Ernst Gellhorn. There he studied the effects of ambient temperature on the EEG and began to use the method of evoked responses to monitor central nervous structures. From Minneapolis he moved to Shrewsbury, Massachusetts, where he joined Peter J Morgane at the Worcester Foundation of Experimental Biology. From very early on, Werner Koella recognized the important role of serotonin in brain mechanisms. Already in 1959, he published the first papers on the effects of serotonin and LSD on evoked potentials. In the following years, serotonin became the major focus of his research, culminating in his most highly cited paper on the effect of serotonin depletion by parachlorophenylalanine on sleep, which he published in 1968 with Feldstein and Czicman. Because at that time serotonin was considered to be the major sleep-promoting transmitter, he suggested jocularly that its name be changed to somnotonin.

After returning to Switzerland in 1968, Werner Koella continued his research at the Department of Biological Research of Ciba-Geigy in Basel. He examined the action of the GABA-B receptor agonist baclofen and investigated potential therapeutic agents of anxiety disorder and epilepsy. Still, hypnotics and mechanisms of vigilance remained at the center of his interest. In 1972, he organized the first European Sleep Research Congress in Basel and became the Founding President of the European Sleep Research Society (ESRS). The new society flourished under his presidency and held its congresses every 2 years in another European city. Werner Koella was instrumental in forging contacts between different groups of basic and clinical research, thereby contributing to the establishment of a sleep research community in Europe. Although his office as ESRS president ended in 1976, he remained a driving force of the society. From 1972 till 1986, he was the editor of the congress proceedings that were published at 2-year intervals as hard-bound volumes.

Werner Koella's wide-ranging expertise in basic and clinical neuroscience is reflected also by the other books he authored (Physiologie des Schlafs 1982), coauthored (Tolerance to Beneficial and Adverse Effects of Antiepileptic Drugs 1986), and coedited (Temporal Lobe Epilepsy, Mania and Schizophrenia and the Limbic System 1982). He was a dedicated teacher and held professorships at Boston University and the University of Berne.

Werner Koella was a man of great energy, assertiveness, and experience, always ready to help. After his retirement, he continued to lead an active life. He was an enthusiastic hiker and trekker, crisscrossing Switzerland on foot several times. At the age of 75, he extolled the rejuvenating effect of these exploits. As an accomplished trumpet player, he was a member of the Basel Brass Choir. His friends, colleagues, and former students will remember Werner as an outstanding neuroscientist, an excellent manager, and a most sociable and generous person. He is survived by his wife Doris and his three sons.