Hsiangtung Chang



Zhang Xiangtong (Hsiang-tung Chang), born on November 27, 1907, neurophysiologist, Member of Chinese Academy of Sciences, Honorary Director and Professor, Institute of Neuroscience, Chinese Academy of Sciences.
Dr. Chang obtained his Ph.D. degree (in Physiology) in Yale University in 1946, he was appointed as an Instructor and later Assistant Professor in Department of Physiology of Yale University School of Medicine in 1948-1952, and Associate of Rockefeller Institute for Medical Research from 1952 to 1956. At the end of 1956 he returned to China and became a Professor in Institute of Physiology, Chinese Academy of Sciences from 1957 to 1980, was appointed as Professor and Director of Shanghai Brain Research Institute of the Academy from 1980 until 1984, and became the Honorary Director of that Institute from 1984 to 1999.
Hsiang-tung Chang is one of the pioneers studying the function of dendrites of central neurons. In early 1950s, he investigated the functional characteristics of apical dendrites of pyramidal neurons in the cerebral cortex with electrophysiological approach. He hypothesized that dendrites were electrically excitable and action potentials could be conducted along apical dendrites. He also emphasized the importance of synapses formed on dendrites: as they are distributed all the way along the dendrites and many are formed with thin dendritic spines, these synapses may not be as efficient as those on the soma in inducing action potentials in postsynaptic neurons. However, he thought they are paramount important for subtly and accurately regulating and adjusting the excitability of the neurons. Hsiang-tung Chang's investigation had large impact at the time and in many years afterwards. His hypothesis that dendrites are able to conduct action potentials, in spite of controversies and objections in more than 30 years, is finally proved to be correct by leading laboratories very recently.
Hsiang-tung Chang has made other important contributions as well. He was included by Encyclopedia of Neuroscience in a name list of scientists who had made important contributions to development of neuroscience in the period before 1950 because of his two classical investigations: Topographical representation of muscles in motor cortex of monkeys and afferent fiber composition in muscle nerves. He found the photic potentiation phenomenon in which a background photic illumination  elevated the excitability of visual as well as auditory cortex.
Hsiang-tung Chang is also a pioneer in the study of neurophysiological basis of acupuncture analgesia. He and his groups' important contribution in this field is the demonstration that inputs from acupuncture stimulation interact with and thus depress pain-inducing signals at various levels of the central nervous system. This provided a good basis for further in-depth study on the mechanisms.