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Evidence of voluntary control of other muscle groups during REM was found by LaBerge, Nagel, Dement, and Zarcone (1981) while testing a variety of lucidity signals. They observed that a sequence of left and right dream-fist clenches resulted in a corresponding sequence of left and right forearm twitches as measured by EMG. However, the amplitude of the twitches bore an unreliable relationship to the subjective intensity of the dreamed action. Because all skeletal muscle groups except those that govern eye-movements and breathing are profoundly inhibited during REM sleep for, it is to be expected that most muscular responses to dreamed movements will be feeble. Nonetheless, these responses faithfully reflect the motor patterns of the original dream. Similar observations have been made by Fenwick et al. (1984).
Following reports of cognitive task dependency of lateralization of EEG alpha activity in the waking state by many researchers, LaBerge & Dement (1982b) undertook a pilot study demonstrating the feasibility of similar investigations in the lucid dream state. The two tasks selected for comparison were dreamed singing and dreamed counting, activities expected to result in relatively greater engagement of the subjects' left and right cerebral hemispheres, respectively.
Integrated alpha band EEG activity was derived from electrodes placed over right and left temporal lobes while four subjects sang and estimated 10 seconds by counting in their lucid dreams (marking the beginning and end of each task by eye movement signals). The results supported the hypothesized lateralization of alpha activity: the right hemisphere was more active than the left during singing; during counting the reverse was true. These shifts were similar to those observed during actual singing and counting. In contrast, a control condition with imagined singing and counting showed no significant laterality shifts. Because of the small number of subjects, the conclusions of this study must be regarded as suggestive at best.
LaBerge & Dement noted an important implication of their results for the interpretation of EEG alpha activity during REM sleep. Since continuous alpha activity occurs when a subject awakens, sleep researchers have usually assumed that increased alpha activity in the context of sleep is always a sign of wakefulness or relative cortical activation. The findings just discussed suggest the contrary: alpha activity during REM sleep is, as in waking, inversely related to cortical activation. When a person awakens from a vivid dream to a dark room, his cortical (occipital, at least) activation has decreased, not increased, with the resultant appearance of elevated alpha power.
In this view, it is a straightforward prediction that occipital alpha power during REM sleep will correlate negatively with subsequently reported dream vividness. This could provide the proper explanation for the finding that awakenings following REM periods with high levels of alpha activity are more likely to yield "thinking" reports than awakenings from low-alpha REM periods which yield more "dreaming" reports (Antrobus, Dement & Fisher (1964).
Sexual activity is a rather commonly reported theme of lucid dreams (Garfield, 1979; LaBerge, 1985). LaBerge, Greenleaf, and Kedzierski (1983) undertook a pilot study to determine the extent to which subjectively experienced sexual activity during REM lucid dreaming would be reflected in physiological responses.
Sixteen channels of physiological data, including EEG, EOG, EMG, respiration, skin conductance level (SCL), heart rate, vaginal EMG (VEMG) and vaginal pulse amplitude (VPA), were recorded from a single subject. The experimental protocol called for her to make specific eye movement signals at the following points: when she realized she was dreaming (i.e., the onset of the lucid dream); when she began sexual activity (in the dream); and when she experienced orgasm.
The subject reported a lucid dream in which she carried out the experimental task exactly as agreed upon. Data analysis revealed a significant correspondence between her subjective report and all but one of the autonomic measures; during the 15 second orgasm epoch, mean levels for VEMG activity, VPA, SCL, and respiration rate reached their highest values and were significantly elevated compared to means for other REM epochs. Contrary to expectation, heart rate increased only slightly and non-significantly.
lucidity
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