HI, I'M CHARLES CZEISLER

(born 1952) I'm an American physician and sleep researcher. I'm a researcher and author in the fields of both circadian rhythms and sleep medicine. 

Focus is the neurobiology of human circadian rhythm. I examines the relationship between the circadian oscillator and sleep homeostasis, and how this interaction affects health. My research interests encompass many areas including body temperature rhythms and the effects of melatonin on humans (2011). I investigates how the physiological system works to reset the circadian pacemaker. My team discovered that light transduced by non-visual input (melanopsin activation) could reset the circadian clock in patients without sight.[9] This indicated that some blind humans can entrain to light through non-visual photoreceptors (2007). I found that intrinsically photosensitive retinal ganglion cells (ipRGCs) influence both the circadian clock and visual perception, indicating that ipRGCs contribute to "visual" light perception even in the absence of rod and cone photoreceptors. Significantly, this challenged the misconception that rod and cone photoreceptors were the sole receptors for photo-entrainment in humans. In 2002, Czeisler published a study that defended the long-held notion that mammals do not have extra-occular photoreceptors. The findings of his study definitively refute those of the famous 1998 Science publication, "Extraocular Circadian Phototransduction in Humans," which found that bright light behind the knees can help regulated human circadian photoentrainment.