Understanding Sleep and Dreaming by William H. Moorcroft

Understanding Sleep and Dreaming by William H. Moorcroft

Author:William H. Moorcroft
Language: eng
Format: mobi, epub, pdf
Tags: Psychology
ISBN: 9780387249650
Publisher: Springer
Published: 2002-01-02T06:00:00+00:00


194

8

Dreaming

Fig. 8.1 The functional

organization of the brain

during REMS showing how it

produces dreaming. Based on

information from

neurophysiological,

neuropsychological and

neuroimaging studies.

Redrawn from (Hobson et al.

2000). Locations of areas in

figure are approximate

8.4.3 Rhythmic Influences on Dreaming

Tore Nielsen (2011), Ph.D., a Professor in the Department of Psychiatry,

University of Montreal where he is the Director of the Dream and Nightmare

Laboratory, has reviewed research that suggests REMS dreaming and NREMS

mentation are shaped by rhythmic influences that emanate from the brain (see Sect.

8.4

The Process of Dreaming

195

3.2.2). These include the 90 min REMS-NREMS ultradian cycle, the sleep-wake circadian rhythm, and the increase in REMS propensity as a night of sleep progresses. While the research done to date is far from conclusive, different aspects of

dreaming seem to be affected, such as the likelihood of a dream or mentation

recall, the length of recall reports, and the intensity of the visual perception.

Nielsen concludes that both the quality and quantity of REMS dreams and

NREMS mentation are varied by one or several ‘‘imagery generators’’ with a

90 min ultradian rhythm. For example, during REMS, dream reports are longest

when obtained during the middle of a REMS period but shorter before or after this;

for NREMS mentation recalls the pattern is just the opposite. That is, the peak of

the ultradian influence is in the middle of the REMS period and lowest during the

middle of the NREMS period. In addition, qualitative aspects such as how vivid,

intense, and dreamlike the recalls are seem also to vary with a 90 min frequency.

Research on REMS dreams and NREMS mentations through the night indicate

circadian and sleep-dependent influences. Changes in the length of dreams as well

as their organization, substance, and how well they are remembered imply cir-

cadian-like variations. Additionally, the reports obtained from the first third of the

sleep period are markedly different in quality from those obtained during

the remainder of the sleep period. For example, REMS dream reports get longer as

the night goes on even if all the reports are gathered after about 5 min into the

REMS period have elapsed. Likewise, the number of events per story, but not the

number of statements in the episode gradually increase during the sleep period.

Also dreams tend to become more realistic and engrossing later in sleep. However,

it is also possible that these qualitative differences may be due to changes in the

length of the reports that also get longer as the night goes on, so these conclusions

have to be considered tentative.

Sleep-dependent influences have also been reported. Compared to shorter

episodes (less than a minute), dreams during longer REMS episodes (over 9 min)

are livelier, more theatrical, and more vibrant, but with more distortion, emo-

tionality, anxiousness, disagreeableness, antagonism, and violence. In addition

there are a greater variety of scenes and more scenes where the imagining is more

clear. Yet elements like believability and reasonableness of the dream remain

constant.

8.5 Conclusion

Dreams, like sleep, occur between two periods of wakefulness. They are influ-

enced by prior waking and can influence subsequent waking. Cartwright captures

this with the title of her book The Twenty-four Hour Mind (2010). Earlier in

history and in other cultures people had other views of the sources of



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