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G Dirlich

Publications and source records attributed to G Dirlich.

27 records · Page 2Linked to original sources
PubMed1976

[Studies on the stability of human ultradian rhythms (author's transl)].

It was investigated whether the REM-NREM (rapid eye movement-non-REM) sleep rhythm has a stable period during long-term observations. Sequences of 17 to 31 consecutive sleep records were analyzed for 6 test subjects and 1 patient. Period stability was confirmed for three experimental conditions: a) undisturbed night sleep, b) inversion of the sleep-waking cycle, c) absence of external timing mechanisms. The period of the ultradian REM sleep rhythm is no integral submultiple of 24 h, so that the remainder causes a daily drift in the REM sleep rhythm. It is assumed that the ultradian process is controlled endogenously. In contrast to the circadian rhythm the ultradian rhythm appears to be free-running under normal conditions. The stability of the ultradian period has been shown in long-term observations.

Circadian Rhythm↗
PubMed1975

Phase shift in the REM sleep rhythm.

The periodic alternation between REM and NREM sleep was analyzed. Usually, sleep records of consecutive nights of a subject are regarded to be independent events. However, it may be that consecutive nights are realizations of a continuously ongoing rhythm. This was tested in the present study. The temporal patterns of REM and NREM sleep in sequences of about 30 consecutive nights for 3 subjects were analyzed. The results show that only the onset of the first REM sleep phase during any one night may be predicted from the sleep onset time, whereas a systematic phase shift between consecutive nights was observed in the later REM sleep phases. Thus, the onset of later REM sleep phases is better predicted by assuming a rhythm with stable period length which controls the appearance of REM sleep phases in successive nights. Under the experimental conditions the phase shift was between 5 and 10 min per 24 hrs for the 3 subjects. The result is accordance with Kleitman's basic rest activity cycle (BRAC) hypothesis.

Adult↗
PubMedDate not supplied

Enhanced long-latency somatosensory potentials in major depressive disorder.

Bodily misperceptions are a frequent symptom in major depressive disorder. A reduced ability to deflect attention from somatosensory stimuli may contribute to the generation of unpleasant bodily sensations and co-occur with altered habituation of the brain electric reactions to somatosensory stimuli. The aim of the present study was to explore whether attention-related components of somatosensory evoked potentials (SSEP) and the habituation of these components are altered in major depression. Fifteen patients with major depressive disorder were compared to an age- and gender-matched group of 15 healthy controls. A series of identical, intrusive but not painful electric stimuli were applied to the left index finger for 48 min. Averaged SSEP were computed from multichannel EEG recordings for consecutive recording blocks of the experiment, each block containing 162 stimuli. Based on these data the habituation process of late components of the SSEP was analysed in two latency intervals (50-150, 170-370 ms). Patients showed significantly enhanced reactions throughout the entire experiment. The persistence of enhanced SSEP components throughout the habituation process may be caused by a deficit in reducing the activity of attention-related brain processes concerned with intrusive, yet behaviourally irrelevant, continued stimulation in the state of major depression.

Adult↗
PubMedDate not supplied

Are biological rhythms disturbed in depression?

In a large-scale investigation of circadian rhythms in endogenous depression, no free-running rhythms or indications of phase-advance were found in the patients compared with themselves after clinical recovery and with healthy controls. They exhibited a reduction of the amplitude of depression scales, partially due to a "ceiling effect" of highly elevated scores. A reduction of the amplitude of body temperature was probably related to a negative masking of the temperature rhythm by e.g. the patients' sleep disturbances. An increase in the amplitude of the cortisol rhythm, due to an elevation of the circadian maximum, was particularly pronounced in patients with significant diurnal variation in the severity of depression. It was thus probably related to a stress-induced positive masking of that rhythm. The acrophases of depression scores and the cortisol rhythm coincided roughly during but not outside depression. This may indicate a circadian modulation of the disease process and the activity of the hypothalamo-pituitary-adrenocortical system by the same clock-like mechanism within the hypothalamus.

Body Temperature↗