Biological clock study challenged. (Biology).A report in the July 26 Science disputes the controversial notion that bright light applied to skin can reset a person's biological clock. In 1998, a research group reported, also in Science, that shining light on the back of a person's knees could delay or advance the brain-driven daily rhythm that influences body temperature, wakefulness wakefulness believed to occur when the tonic flow of impulses from the reticular activating system exceeds the critical level for sustaining consciousness; reduction of reticular activating system activity is the basis of the pharmacological induction of sedation. , and many other physiological features. The discovery was hailed as potentially a new way to treat jet lag jet lag Period of adjustment of biological rhythm after moving from one time zone to another, experienced as fatigue and lowered efficiency. It reflects a delay in the synchronization of changes in the level of blood cortisol, the major steroid produced by the adrenal cortex and other disruptions of the body's biological clock (SN: 7/11/98,p. 24). The study, however, prompted skepticism from many researchers. Some suggested that the test subjects didn't have their eyes properly shielded from light. Conventional thinking holds that light gathered by the eye is the only way to entrain entrain /en·train/ (en-tran´) to modulate the cardiac rhythm by gaining control of the rate of the pacemaker with an external stimulus. the body's internal timepiece. In the new work, Kenneth P. Wright Jr. and Charles Czeisler of Brigham and Women's Hospital Brigham and Women's Hospital (BWH) is a hospital in the Longwood Area of the Boston, Massachusetts neighborhood of Mission Hill. With Massachusetts General Hospital, it is one of the two founding members of Partners HealthCare. in Boston tried to duplicate the original study, while taking extra steps to prevent participants from seeing any light. Shining light behind a person's knees had no effect on his or her biological clock, they found. The "suggestion that photic photic /pho·tic/ (fo´tik) pertaining to light. pho·tic adj. 1. Of or relating to light. 2. Penetrated by or receiving light. 3. signals are carried from the back of the knee to the human brain via the circulatory system is not supported by our data," they conclude.--J.T. |
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