Dreaming – motivated or meaningless?

Mark Blagrove

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Mark Blagrove on a land still stubbornly slow to offer up its secrets.

There are two widely held views about dreams. One view is that they contain information about our waking life, including our waking cognition and emotions, and possibly even some information that we are motivated to ignore when awake: On this view, dreams are worth examining. The other view is that dreaming is a delirium, dreams are senseless and any ‘information’ in them is likely to be misleading, having little connection to reality: On this view, dreams are best ignored. These two views are each widely held in the lay population, and amongst psychologists (see authors included in Pace-Schott et al., 2003).
Dreams can be defined as the images and thoughts that are experienced during sleep.
Approximately 14 per cent of people report dreaming every night, and 6 per cent report never dreaming; dream recall frequency decreases with age (Strauch & Meier, 1996). Positive interest in dreams is associated with higher dream recall, but despite many studies over the last decades very few personality correlates of frequency of dream recall have been found (Blagrove, 2007). It is thus unclear why some people report more dreams than others. People who are more creative have been found to recall more dreams, and to report more dreams that are bizarre, but it is not clear if their dream content and actual occurrence of dreams are different from those of less creative people; they may have a greater interest in dreams than less creative people, and thus may just be more willing to report bizarreness or to retrospectively report a high frequency of dreaming (Blagrove, 2007). Individual differences in dream content salience and intensity have been proposed to account for the fact that some people report more frequent dreams than others, but this hypothesis is problematic because the salience of dream content is difficult to assess independently of dream recall.

Dreaming and the brain

Sleep in humans is divided into light sleep (stages 1 and 2), deep sleep (stages 3 and 4), and rapid eye movement sleep (REM sleep). REM sleep occurs approximately every 90 minutes, each REM period becoming longer across the night; the last REM period can be as long as 40 minutes, the first as short as 5 minutes. These eye movements can be visible to a person watching. Brainwaves during REM sleep have some similarity to waking brainwaves, and some parts of the brain are very active, while muscle tone is very low; for this reason, REM sleep has been termed paradoxical sleep.
Aserinsky and Kleitman (1953) found that dream recall was more likely if people were woken from REM sleep than from sleep stages 1 to 4 (non-REM sleep). However, in 1962 Foulkes showed that dreams can occur in non-REM sleep but that they were usually shorter and less dramatic and vivid than REM dreams. It is currently a matter of dispute whether differences between REM and non-REM dreams are just due to non-REM dreams being shorter on average than REM dreams, or due to non-REM sleep not allowing the recall of dreams as well as does REM sleep, or whether there are fundamental differences between the two types of sleep in how they produce dreams (Nielsen, 2000). For example, Hobson et
al. (2000) propose a cholinergic neurochemical difference between REM sleep and both wake and non-REM sleep, to explain the amnesic and irrational nature of REM dreams. In various studies since the 1970s Hobson has proposed a physiological basis for other dream characteristics, such as the activation in REM sleep of areas of the parietal lobe being related to visual imagery, activation of the amgydala and paralimbic cortex in REM sleep causing the emotionality of dreams, and random stimulation of the cortex by the brainstem during REM sleep causing scene changes and bizarreness. Hobson’s early activation-synthesis theory of dreaming holds that memories are randomly stimulated by the periodic brainstem activation during REM sleep, with the disparate images being synthesised by the cortex to make a more sensible plot.
However, Solms (1997) points out that whereas non-REM dreams are on average shorter than REM dreams, 20 per cent of non-REM dreams are indistinguishable from REM dreams, and, indeed, many of the characteristics of REM dreams occur also in non-REM dreams. Hobson’s recent work (e.g. Hobson et al., 2000) tries to account for this. Solms shows from his own work and from over a century of the neuropsychological literature that lesions to the ventral-mesial quadrant of the frontal lobe, which is involved with emotional motivation and wishes, or to the parietotemporo-occipital junction (a sensory area), results in the loss of dream recall, but with REM sleep preserved. These brain areas thus seem to be important for creating dreams, with dream production being independent of REM sleep. A debate between Solms and Hobson on whether dreaming is especially associated with REM sleep can be purchased via www.dreamdebate.com.

Dream content

Specific emotions or moods occur in 75 per cent of dreams, with positive and negative emotions occurring equally often across individuals, joy being the most common single emotion, and anger and fear as next most common (Strauch & Meier, 1996). When an unselected sample of all dreams over a period is collected from an individual, rather than relying on the recollection of particular interesting dreams, or their impression of their dreams in general, bizarreness is found to occur infrequently, in only about 10 per cent of dreams.