How Physiological Correlates to Hypnologic Experiences

When subjects are interrupted upon falling asleep and asked to report on any mental activity that might have been taking place, they usually have something to say about what was going on in their mind. Foulkes and Vogel (1966) describe a laboratory study in which standard EEG/EOG recordings were made and the subjects were questioned after periods of wakefulness, stage 1 sleep and stage 2 sleep. There was no clear relation between depth of sleep, as indicated by these measures, and the incidence of reports. Subjects came up with well-organized fantasy sequences after being roused from periods with high levels of EEG alpha and saccadic eye movements, consistent with relaxed wakefulness, but it was difficult to distinguish these reports from those which were more dreamlike and elicited from subjects roused from deeper levels of sleep.

The experimenters categorized the experiences in relation to the sensory modality principally involved and the connectedness of the plot. One example, of a 'dream' in the state of relaxed wakefulness, reads more like a fantasy of wish-fulfillment than a sleeping dream account, although others were remarkably dreamlike. Reports of thinking and directed imagery were also elicited from subjects woken from light stage 2 sleep.

There were, however, consistent differences in the quality of experience as wakefulness gave way to sleep. The subjects began to feel a loss of control over the course of their thinking. Their awareness of being in a laboratory declined, and similarly their awareness that they were under instruction to observe their own sensations become less strong.

Thinking and fantasizing seem to have constituted the majority of Foulkes and Vogel's subjects' reports, but while it was possible to make fine distinctions between degrees of sleep depth, using EEG/EOG measures, these did not seem to be very predictive of the quality of experience reported. Most surprising, perhaps, were the numbers of reports of 'everyday' thinking from subjects who were undoubtedly asleep, according to psycho physiological criteria. In addition, there were some reports of dreaming during wakefulness and light slow-wave sleep that were bizarre, quite well organized in terms of plot and involving unusual visual imagery - just like the fully fledged dreams of REM sleep.

Any hope of a unique syndrome of EEG/EOG patterns that might be associated with the odd experiences reported by McKellar's (1972) subjects must be abandoned. As we fall asleep our mental state becomes somewhat unpredictable and immune to such gross measures. Sometimes we appear to ourselves to be making sense, sometimes we seem to be obviously deranged and sometimes our thoughts are driven by the vivid imagery of dreams. The psycho physiologist cannot as yet match the experiences of going to sleep with the measures of brain function that are currently available. While the majority of us, if not all, probably have hypnologic experiences of the sort reported by McKellar, they were by no means typical of Foulkes and Vogel's drowsy subjects, and must represent the more memorable events in most people's half-sleeps, rather than the most common.