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Biomedical subjects

Michael Schredl

Publications and source records attributed to Michael Schredl.

At least 19 recordsLinked to original sources
PubMed2007

Dreaming in posttraumatic stress disorder: A critical review of phenomenology, psychophysiology and treatment.

This review summarizes the available knowledge on the phenomenology of posttraumatic dreams. Posttraumatic nightmares are reported by up to 70% of individuals suffering from posttraumatic stress disorder (PTSD). An extensive review of polysomnographic studies suggests that neither this high incidence nor the occurrence of posttraumatic nightmares throughout the sleep cycle can be explained by altered REM sleep parameters. The assumption that a reduction of dream recall may serve as a coping mechanism in PTSD patients is questionable. About 50% of posttraumatic dreams comprise exact replications of the traumatic events. Therefore dreams in PTSD do not have stereotypical content. Data characterizing non-replicative posttraumatic dreams and indicating a change in dream content over time must be considered preliminary. Occurrence of posttraumatic dreams is associated with psychopathological developments. Imagery Rehearsal Therapy has repeatedly been proven to be a valuable tool in treating patients suffering from posttraumatic dream disturbance. A deeper knowledge of posttraumatic dreams is essential for any theory of PTSD as well as for a better understanding of the overall function of dreaming.

Adult↗
PubMed2006

The relationship between REM sleep and memory consolidation in old age and effects of cholinergic medication.

BACKGROUND: Recent findings in young adults suggest that rapid eye movement (REM) sleep plays a role in procedural memory consolidation. The significance of REM sleep for memory consolidation in old age has not yet been investigated. METHODS: Effects of REM sleep manipulation on declarative and procedural memory consolidation were investigated in 107 healthy older adults, ages 60-82 years. Rapid eye movement sleep deprivation was achieved by REM sleep awakenings and compared with non-REM sleep awakenings. Rapid eye movement sleep augmentation was realized physiologically by REM sleep rebound and pharmacologically by administering an acetylcholinesterase inhibitor in a double-blind, placebo-controlled design. Memory performance was tested by a paired associate list and a mirror tracing task at 9:30 pm and 7:30 am with sleep intervening between 11:00 pm and 7:00 am. RESULTS: Although REM sleep deprivation led to a significant reduction in total and phasic REM sleep, memory consolidation remained unaffected. Both REM sleep augmentation groups showed a significant increase in phasic REM sleep, whereas only pharmacological cholinergic REM sleep manipulation exerted a significant positive effect on procedural memory consolidation. CONCLUSIONS: Because only after cholinergic stimulation of phasic REM sleep procedural memory consolidation is improved, cholinergic activation seems to be a crucial component of REM sleep-related memory consolidation in old age.

Aged↗
PubMed2006

Sleep quality in adult patients with attention deficit hyperactivity disorder (ADHD).

Sleep disorders are common in adults with attention deficit/hyperactivity disorder (ADHD). Two sleep questionnaires; the Brown ADD Scale, the Symptom-Checklist-90-R, and a self-developed symptom questionnaire were administered in this study. In a sample of 61 patients without comorbidity, current substance abuse and medication intake, sleep problems were reported more often than in healthy controls. A lack of being refreshed in the morning was very closely associated with ADHD symptomatology whereas insomnia was related to the presence of comorbidity and depressive symptoms. In the total sample (N = 120), medication intake (mainly stimulants) was not related to any of the sleep parameters. It seems important to screen adult patients with ADHD for the presence of sleep disorders, especially insomnia, restless legs syndrome, and sleep-related breathing disorders (the last in conjunction with the body mass index). Since primary sleep disorders are associated with cognitive impairment, one might expect that ADHD symptomatology may improve if comorbid sleep disorders are adequately treated in addition to the specific ADHD treatment.

Adolescent↗
PubMed2006

Nightmares and oxygen desaturations: is sleep apnea related to heightened nightmare frequency?

In the 19th century, several authors held the view that nightmares are caused by oxygen shortage. The present study was designed to study nightmare frequency in patients with obstructive sleep apnea syndrome and its relationship to respiratory parameters. A brief questionnaire was administered to 323 patients with sleep apnea syndrome before their first laboratory night. The reduction in nightmare frequency in the sleep apnea group was explained by the reduced dream recall frequency. Despite some illustrative examples of a correlation between oxygen desaturation and dream content, the respiratory parameters as measures of sleep apnea syndrome severity did not correlate substantially with nightmare frequency. Psychiatric comorbidity and an intake of psychotropic medication were associated with heightened nightmare frequency in this sample. It must be concluded that the oxygen hypothesis did not play a major role in explaining the occurrence of nightmares. As this might be partly explained by adaptation to the nightly desaturation periods, it will be fruitful to apply experimental procedures that interrupt airflow during (rapid eye movement) REM sleep for short periods in a systematic way without the knowledge of the sleeper and to then study their effects on dream content. Some patients reported a correlation between daytime stressors and nightmares, which is in line with modern etiological models of nightmares.

Adult↗
PubMed2006

Dream recall and the full moon.

There is ongoing debate on whether the full moon is associated with sleep and dreaming. The analysis of diaries kept by the participants (N = 196) over 28 to 111 nights showed no association of a full moon and dream recall. Psychological factors might explain why some persons associate a full moon with increased dream recall.

Adult↗
PubMed2006

Dream recall and nightmare frequency: a family study.

The present study investigated dream recall as well as nightmare frequency in families. Whereas a positive correlation for nightmare frequencies between children and mothers was found (but not for children and their fathers), the relationship for dream recall frequency was small and nonsignificant. Assuming that mothers are still the primary caregivers in the modern family, and, thus, might encourage or discourage children to talk about their dreams, the findings of the study support Cohen's 1973 hypothesis of a socialization effect on nightmare frequency and maybe a smaller effect on dream recall frequency.

Adult↗
PubMed2006

[Treatment of nightmares].

Childhood nightmares are a common phenomenon; the prevalence rates indicate that up to 5% of the children suffer from quite frequent nightmares. The etiology of nightmares is best explained by a vulnerability/stress model but one has to take cognitive avoidance as a maintaining factor into consideration. The therapeutic approach consisting of confrontation, coping and training is easily applied--even by non-professionals--and the efficacy has been demonstrated for adult nightmare sufferers.

Child↗
PubMed2005

Nightmares: from anxiety symptom to sleep disorder.

The DSM-IV-TR definition of nightmares-extremely frightening dreams from which the person wakes up directly-is unnecessarily narrow. Other emotions (anger, grief) have also been reported in nightmares, and direct awakening from a bad dream seems to be unrelated to increased distress. In addition, assessment of nightmares is problematic. Polysomnographic recordings have an ameliorating effect on nightmare frequency, retrospective measurements tend to underestimate nightmare frequency, and persons with frequent nightmares may feel reluctant to fill out (daily) prospective measurements. For studying nightmares, it is necessary to distinguish idiopathic nightmares from posttraumatic nightmares, which are part of a posttraumatic stress reaction or disorder that may result from experiencing a traumatic event. Both types of nightmares have been associated with an elevated level of periodic limb movements, although only posttraumatic nightmares seem to be related to more and longer nocturnal awakenings. Nightmares have also been repeatedly associated with the general level of psychopathology, or the so-called personality factor neuroticism. Nightmare distress, the impact on daily functioning caused by nightmares, may function as a mediating variable. Several studies in the last decades have shown that nightmares can be treated with several cognitive-behavioral techniques. The cognitive-restructuring technique imagery rehearsal therapy is the treatment of choice for nightmares, although a randomized controlled trial with an attention control-group has not yet been carried out. Nightmares are more than a symptom of a larger (anxiety) syndrome and need to be viewed from a sleep medicine perspective: nightmares are a highly prevalent and separate sleep disorder that can and should receive specific treatment.

Anxiety↗
PubMed2005

Manipulating REM sleep in older adults by selective REM sleep deprivation and physiological as well as pharmacological REM sleep augmentation methods.

Experimental approaches to manipulate REM sleep within the cognitive neuroscience of sleep are usually based on sleep deprivation paradigms and focus on younger adults. In the present study, a traditional selective REM sleep deprivation paradigm as well as two alternative manipulation paradigms targeting REM sleep augmentation were investigated in healthy older adults. The study sample consisted of 107 participants, male and female, between the ages of 60 and 82 years, who had been randomly assigned to five experimental groups. During the study night, a first group was deprived of REM sleep by selective REM sleep awakenings, while a second group was woken during stage 2 NREM sleep in matched frequency. Physiological REM sleep augmentation was realized by REM sleep rebound after selective REM sleep deprivation, pharmacological REM sleep augmentation by administering an acetylcholinesterase inhibitor in a double-blind, placebo-controlled design. Deprivation and augmentation paradigms manipulated REM sleep significantly, the former affecting more global measures such as REM sleep minutes and percentage, the latter more organizational aspects such as stage shifts to REM sleep, REM latency, REM density (only pharmacological augmentation) and phasic REM sleep duration. According to our findings, selective REM sleep deprivation seems to be an efficient method of REM sleep manipulation in healthy older adults. While physiological rebound-based and pharmacological cholinergic REM sleep augmentation methods both failed to affect global measures of REM sleep, their efficiency in manipulating organizational aspects of REM sleep extends the traditional scope of REM sleep manipulation methods within the cognitive neuroscience of sleep.

Aged↗
PubMed2005

Dream recall and sleep duration: state or trait factor.

Previous research regarding the relationship between habitual sleep duration and frequency of dream recall yielded conflicting results, whereas experimental manipulation of sleep duration showed a significant effect on dream recall. In this study analyzing both effects simultaneously, the findings from diaries kept by the 196 participants over 28 to 111 days indicated that intra-individual fluctuations in sleep duration were significantly related to dream recall whereas interindividual differences in dream recall were not associated with differences in sleep duration. Sleep inertia might be an explanation for this finding.

Adult↗
PubMed2004

Reliability and stability of a dream recall frequency scale.

Dream recall frequency varies widely between people as well as within individuals. To explore the relationship between dream recall frequency and trait variables such as personality dimensions, a measure of stable interindividual differences is necessary. In the present study (N = 198 patients with sleep disorders; 115 women, 83 men; M age = 45.8 +/- 15.3 yr.) a high retest reliability of the 7-point Dream Recall Frequency scale developed by Schredl in 2002a was found. If the participants' focus was not directed explicitly towards dream recall when the scale was presented within a general sleep questionnaire, the hitherto-reported increase of dream recall due to measuring dream recall frequency did not occur. In conclusion, the present scale is well suited for measuring interindividual differences in dream recall frequency reliably.

Dreams↗
PubMed2004

Seasons in dreams.

Based on the continuity hypothesis of dreaming, whether season-related themes are more often found in five dreams collected over a 2-wk. period in particular seasons was examined for 376 women and 68 men. Whereas for winter-related themes the continuity hypothesis was supported, the percentage of summer-related themes did not differ between dream samples collected in the winter or summer months, respectively. Researchers should include the amount of time spent with season-related activities, conversations, and films to test whether in dreams the relation is direct between waking life and dreaming about seasons.

Dreams↗
PubMed2004

Time required for motor activity in lucid dreams.

The present study investigated the relationship between the time required for specific tasks (counting and performing squats) in lucid dreams and in the waking state. Five proficient lucid dreamers (26-34 yr. old, M=29.8, SD=3.0; one woman and four men) participated. Analysis showed that the time needed for counting in a lucid dream is comparable to the time needed for counting in wakefulness, but motor activities required more time in lucid dreams than in the waking state.

Adult↗
PubMed2004

Typical dreams: stability and gender differences.

Although the variability of dream content is large, typical dream themes that occur quite often and are reported by many people can be identified (e.g., being chased, falling, flying, failing an examination, being unable to find a toilet or restroom). The present study is an investigation of the stability of the rank order of the dream themes and of gender differences in the content of dreams. The authors administered A. L. Zadra and T. A. Nielsen's (1997) Typical Dream Questionnaire to 444 participants. The findings indicated that most of the 55 dream themes occurred at least once in most of the participants' lifetimes. In addition, the correlation coefficients for the rank order of the themes were very high; that is, the relative frequencies were stable. The gender differences in the present study were in line with content analytic findings; for example, men reported dreams about physical aggression more often than did women. Overall, previous research and the present data indicate that available research results of the measurement of typical dream themes are reliable and valid. The question of the meaning of these themes or the relationship between typical dream contents and waking life experiences, however, has not yet been answered and is open to future research.

Adult↗
PubMed2003

Effects of state and trait factors on nightmare frequency.

In a new approach, this study compared the effects of trait and state factors on nightmare frequency in a non-clinical sample. Although neuroticism and boundary thinness were related to nightmare frequency, regression analyses indicated that the trait measures did not add to the variance explained by the state measures. This finding supports the so-called continuity hypothesis of dreaming, i. e., nightmares reflect negative waking-life experiences. Second, the moderate relationship between nightmare frequency and poor sleep quality was partly explained by the day-time measures of neuroticism and stress, but it can be assumed that nightmares are an independent factor contributing to complaints of insomnia. Longitudinal studies measuring nightmare frequency and stress on a daily basis will shed light on the temporal relationship between daytime measures and the occurrence of nightmares. It will be also very interesting to study the relationship between stress and nightmare frequency in a sample who have undergone cognitive-behavioral treatment for nightmares.

Adolescent↗
PubMed2003

Continuity between waking activities and dream activities.

Empirical studies largely support the continuity hypothesis of dreaming. Despite of previous research efforts, the exact formulation of the continuity hypothesis remains vague. The present paper focuses on two aspects: (1) the differential incorporation rate of different waking-life activities and (2) the magnitude of which interindividual differences in waking-life activities are reflected in corresponding differences in dream content. Using a correlational design, a positive, non-zero correlation coefficient will support the continuity hypothesis. Although many researchers stress the importance of emotional involvement on the incorporation rate of waking-life experiences into dreams, formulated the hypothesis that highly focused cognitive processes such as reading, writing, etc. are rarely found in dreams due to the cholinergic activation of the brain during dreaming. The present findings based on dream diaries and the exact measurement of waking activities replicated two recent questionnaire studies. These findings indicate that it will be necessary to specify the continuity hypothesis more fully and include factors (e.g., type of waking-life experience, emotional involvement) which modulate the incorporation rate of waking-life experiences into dreams. Whether the cholinergic state of the brain during REM sleep or other alterations of brain physiology (e.g., down-regulation of the dorsolateral prefrontal cortex) are the underlying factors of the rare occurrence of highly focused cognitive processes in dreaming remains an open question. Although continuity between waking life and dreaming has been demonstrated, i.e., interindividual differences in the amount of time spent with specific waking-life activities are reflected in dream content, methodological issues (averaging over a two-week period, small number of dreams) have limited the capacity for detecting substantial relationships in all areas. Nevertheless, it might be concluded that the continuity hypothesis in its present general form is not valid and should be elaborated and tested in a more specific way.

Adult↗
PubMed2003

Factors of home dream recall: a structural equation model.

Previous research has indicated that personality factors such as openness to experience, creativity, visual memory, attitude toward dreams, and sleep behavior is related to home dream recall frequency (DRF). However, a study investigating all areas simultaneously within one sample in order to determine the percentage of variance explained by all variables and to take intercorrelations between the influencing factors into account has not been performed till now. The present study with 444 participants fills this gap. Using several indicators for each of the variables mentioned above, a structural equation model was tested. Although the model fit was satisfying, the four factors which were significantly related to DRF: personality (openness to experience, thin boundaries, absorption), creativity, nocturnal awakenings, and attitude toward dreams, explained only 8.4% of the total variance. As this value is considerably lower than those of studies investigating a single influencing factor and using similar measurement instruments in similar samples, one might speculate about possible expectancy effects in these previous studies, an effect which has been demonstrated for DRF in the laboratory setting. In addition, the small percentage of explained variance of each single factors (<3%) may indicate that other, in this study unmeasured, variables such as sleep duration (state aspect), introspection, and cognitive functioning immediately upon awakening (sleep inertia) show substantial covariance with the interindividual differences in DRF. Future studies should focus on longitudinal aspects in order to differentiate between state versus trait factors (although methodologic issues, e.g. the effect of the measurement technique on DRF itself, have to be clarified) and investigate additional variables which might be associated with DRF (see above).

Attitude↗