Phase Response Experiments: First consider a control where an organism is demonstrating a cycling (appx 24 hours) of some physiological feature under constant conditions. For example a sleep wake cycle of a mouse in constant dark and with constant temperature; or the leaf movement of a plant in constant dim light and constant temperature. Now ask what happens if during those constant conditions an experimenter applies some perturbatiuon that one suspects might influence the circadian clock. For example turning on the lights for five minutes, or raising the temperature 10°C for 2 hours, or applying a drug for three hours. When one applies such a perturbation, it is common to observe that the time at which an event occurs (i.e. the phase) is often now different than a control that did not receive the perturbation. This is called a phase shift and is usually measured in hours from the control (or in degrees from a 360° cycle or in circadian time). One usually finds that the magnitude of the phase shift usually depends on the time in the cycle at which the perturbation was applied.
A Phase Response Curve (PRC) is a plot of the magnitude of phase shifting due to a pulse versus the time at which the pulse was applied. Experimenters have determined phase response curves for many organinsims, many oscillating types of physiology, and using many forms of pertubation. Carl Johnson of Vanderbilt University has compiled the data for most of the published phase response curves and has termed the compilation the PRC Atlas. With my help, that data has been put into computer format and is available for the asking. The best way to view the data is via the Hypercard PRC Atlas that can be downloaded from Carl Johnson's web site.
You can get the text format of the data by downloading one of the formats below. In this case you willl have to put the data into your own plotting program to see the actual plots. The data is fairly well structured so that it should be easy to insert into your favorite data spreadsheet program.
Excel 4.0 text file of PRC Atlas data.
PC windows text file of PRC Atlas data.
PC DOS text file of PRC Atlas data.
If you have comments or suggestions, email me at goochv@morris.umn.edu
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Last updated March 17, 2000