Ken-Ichi Honma

Ken-Ichi Honma (born in November 10, 1946) is a Japanese chronobiologist who researches the biological mechanisms underlying circadian rhythms. After graduating from Hokkaido University School of Medicine, he practiced clinical psychiatry before beginning his research. His recent research efforts are centered around photic and non-photic entrainment, the structure of circadian clocks, and the ontogeny of circadian clocks. He often collaborates with his wife, Sato Honma, on work involving the mammalian suprachiasmatic nucleus (SCN).

He was born in Sapporo, Hokkaido, and currently lives with Sato Honma, his wife, in Japan, with their only daughter.

Honma was the former vice-president of the Japanese Society of Sleep Research (2007–2021), the former council chair of the Japanese Society for Chronobiology (2005–2011). Honma is the chairman of the Sapporo Symposium on Biological Rhythms (1995–present), which holds an international symposium centered around chronobiology biannually. He served as the head of a Japan-U.S. joint project on Biological Timing, where he was responsible for sending many Japanese scientists to the United States (1993–1995). While he was the president-elect of the Japanese Society of Chronobiology (2005 to 2010), he co-organized the biannual meetings of the European Biological Rhythms Society (EBRS) and held the first world congress of chronobiology in 2003 at Sapporo as the founding president of the World Federation for Societies of Chronobiology (2001–2011). He has tried to establish a forum among Chronobiologists in Asia as the council chief of the Asian Forum on Chronobiology (2015).

Awards and honors In 2020, Honma received the SRBR Director’s Award for mentoring. The SRBR Award honors members of the Society for Research on Biological Rhythms for their contributions.

Scientific contributions Honma has authored over 200 scholarly articles and has published several edited volumes in the field of chronobiology.

Initially, his research revolved around understanding the photic and non-photic entrainment of circadian rhythms and raised hypotheses about the role of feeding in the entrainment of the circadian clock, as well as the ways in which endogenous rhythms can entrain to artificial bright light before later focusing on uncovering the structure of the circadian clock. Earlier in his career, Honma made the discovery that body temperature, locomotor activity, and plasma levels of corticosterone—all circadian processes—are likely coupled to one common internal oscillator in rats. However, his current research is centered around the ontogeny of circadian rhythms and understanding the physiological aspects of chronobiology.

Earlier works Honma described "a phase response curve (PRC) to a single bright light pulse in human subjects living under isolation." He developed a model in animals for a sleep-wake cycle that is desynchronized from other circadian rhythms in the body such as the plasma levels of melatonin.

Later works In 2014, Honma and his colleagues published a paper that highlighted the effects of postnatal light on cryptochrome-deficient mice. The authors showed that exposure to constant light by placing newborn mice in constant light for three weeks after they were born can partially restore rhythms in the SCN, even though the mice lose sleep-wake rhythms upon weaning. The authors demonstrated that physical activity could also shift the plasma levels of melatonin.

In 2019, Honma, with his collaborators, uncovered the role of GABAergic neurons in inhibiting cells in the suprachiasmatic nucleus (the central oscillator in mammals). They concluded that GABA neither establishes nor maintains circadian patterns in the body, but rather that it "refine the circadian firing rhythm to ensure noiseless communications with neurons outside the SCN."