eval pacemakers Flashcards
Ethics
Animal studies of the sleep/wake cycle are justified because there are very similar mechanisms at work across species. The existence of an SCN and pineal gland in the brains of, say, chipmunks and hamsters, means that generalisations can be made to the human brain, as the mammalian brain has similar structures. This is because such processes occur at a biological level and have evolved as adaptive mechanisms in all species.
However, a more disturbing issue is the ethics involved in such research. The animals in, for instance, the DeCoursey et al. study (facing page) were exposed to considerable risk when they were returned to their natural habitat because their sleep-wake cycles had been altered, and most were killed by predators as a result. Critics of animal research, such as animal rights campaigners, would take issue with such research.
This suggests that studies of this nature which place animals at considerable risk are difficult to justify. Although what we learn from these studies can be applied to the human sleep/wake cycle, researchers should find ways to investigate the effects of endogenous pacemakers that do not endanger the animals studied.
Beyond the master clock
One limitation of SCN research is that it may obscure other body clocks.
Research has revealed that there are numerous circadian rhythms in many organs and cells in the body. These peripheral oscillators are found in the organs including the lungs, pancreas and skin. They are influenced by the actions of the SCN, but also act independently. Francesca Damiola et al. (2000) demonstrated how changing feeding patterns in mice could alter the circadian rhythms of cell in the liver by up to 12 hours whilst leaving the rhythms of the SCN Unaffected.
This suggests other complex influences on the sleep/wake cycle.
Interactionist system
Another limitation is that endogenous pacemakers cannot be studied in isolation.
Total isolation studies, such as Michael Siffre’s cave study (see page 46) are extremely rare.
Remember also that Siffre made use of artificial light which could have reset his biological clock every time he turned his lamp on. in everyday life, pacemakers and zeitgebers interact, and it may make little sense to separate the two for the purpose of research.
This suggests the more researchers attempt to isolate the influence of internal pacemakers, the lower the validity of the research.
