It turns out that the suprachiasmatic nucleus (SCN) is not the only circadian clock in the body. We recently found that the choroid plexus clock exceeds even the SCN clock in terms of robustness (2018) and the kidney clock can influence the behavioral circadian rhythms, potentially through feedback to the master clock (2019). These investigations recast the role of the SCN as the master coordinator of the distributed local circadian clocks, rather than the master pacemaker, and let us think that the circadian organization of the body is likely democratic, and not strictly hierarchical.



References
· The kidney clock contributes to timekeeping by the master circadian clock (2019)
· The choroid plexus is an important circadian clock component (2018)

While a single cell is fully capable of maintaining a circadian clock, evolution chose a multi-cellular clock system in mammals. We have previously found that the main circadian clock, the suprachiasmatic nucleus (SCN), can be reduced to a simple neural circuit of two oscillators. The two-oscillator model predicts novel stability pockets that enable previously unforeseen circadian behaviors. These new insights provide us with specific model-based strategies that we can test in vivo and ex vivo. We seek clinical applications of these findings to quickly stabilize circadian rhythms under unusual seasonal conditions or after abrupt transitions to a new day-night cycle.

Reference
· Love and hate of two circadian clocks (2018)
· Encoding seasonal information in a two-oscillator model ... (2018)
· GABA-mediated repulsive coupling ... (2015)


Emergence of circadian clocks
MOST PPG project with NCKU

The society of circadian clocks emerge slowly and sequentially over the developmental time course. We track and consider this emergence time course in light of preterm development in the neonatal intensive care unit (NICU).

References
· Development of Circadian Clock Functions (2021)

The seasonality is an important cue for mood fluctuation, as evidenced by a seasonal peak of suicide rate among the major depression and affective disorder patients (let us recite T.S. Eliot's "April is the cruelest month"). Psychological studies show that the second-to-minute scale time perception can be a good indicator of the mood state. There is strong evidence that the perceived time length is a function of dopamine and serotonin release, which are likely to be regulated by circadian and seasonal rhythms. We are putting these clues together to understand how circadian rhythms modulate degrees of time perception and distinct mood states. These studies have substantial potential to open up new avenues of treatment for abnormal mood conditions.

References
· Philosophizing and Physiologizing on Time and Mood in the Brain (2016)
· Institute for Advanced Study in Berlin Year Book 2016/2017. pp.157-159.
· A neuroscientist's "brief history of time" (2017)