Misalignments of rest-activity rhythms in inpatients with schizophrenia.

AIMS: Rest-activity rhythms of human beings generally synchronize to a 24-h time cue. Very few detailed research studies have examined rest-activity rhythms in patients with schizophrenia. The present study aimed to explore (i) rest-activity rhythms in patients with schizophrenia, and (ii) factors relevant to their rhythm characteristics. METHODS: We selected only inpatients for this research, because the time cue for inpatients was considered more standardized than that of outpatients. Sixteen inpatients with schizophrenia wore an ActiTrac accelerometer-based activity monitor (IM Systems Inc., Baltimore, USA) for eight consecutive days to measure their activity. We used a chi(2) periodogram to compute rest-activity rhythms from the activity data, whereby the chi(2) value amplitude was regarded as an index of regularity. We conducted non-parametric tests to identify factors relevant to rhythm cycles and patterns. RESULTS: Half of the participants exhibited prolonged rest-activity cycles, and 25% also had irregular rest-activity patterns defined by insufficient chi(2) value amplitude, even though they were clearly under a 24-h time cue. Participants with misaligned rest-activity rhythms had attended daytime non-medical treatment programs less frequently, and had received more anti-anxiety/hypnotic medications than those with proper rhythms. CONCLUSION: Changes in rest-activity rhythms by optimizing pharmacological and non-pharmacological treatment could improve social adjustment or quality of life in patients with schizophrenia.

Effect of voluntary attention on auditory processing during REM sleep.

STUDY OBJECTIVES: The study investigates whether there is an effect of voluntary attention to external auditory stimuli during rapid eye movement (REM) sleep in humans by measuring event-related potentials (ERPs). DESIGN: Using a 2-tone auditory-discrimination task, a standard 1000-Hz tone and a deviant 2000-Hz tone were presented to participants when awake and during sleep. In the ATTENTIVE condition, participants were requested to detect the deviant stimuli during their sleep whenever possible. In the PASSIVE sleep condition, participants were only exposed to the tones. ERPs were measured during REM sleep and compared between the 2 conditions. SETTING: All experiments were conducted at the sleep laboratory of Hiroshima University. PARTICIPANTS: Twenty healthy university student volunteers. INTERVENTIONS: N/A. MEASUREMENTS AND RESULTS: In the tonic period of REM sleep (the period without REM), P200 and P400 were elicited by deviant stimuli, with scalp distributions maximal at central and occipital sites, respectively. The P400 in REM sleep showed larger amplitudes in the ATTENTIVE condition, whereas the P200 amplitude did not differ between the 2 conditions. No effects on ERPs due to attention were observed during stage 2 sleep. CONCLUSIONS: The instruction to pay attention to external stimuli during REM sleep influenced the late positive potentials. Thus electrophysiologic evidence of voluntary attention during REM sleep has been demonstrated.

Comparison of the event-related potentials between tonic and phasic periods of rapid eye movement sleep.

The event-related potentials (ERP) of eight young healthy volunteers were recorded during wakefulness and rapid eye movement (REM) sleep using an auditory discrimination task. REM sleep was classified into phasic and tonic periods according to the presence or absence of REM. In wakefulness, deviant stimuli elicited a P300 that was maximal over parieto-central areas. During the tonic period of REM sleep, deviant stimuli elicited a P200 and a P400. The P200 was distributed more anteriorly and the P400 was distributed more posteriorly than the P300; however, no prominent ERP components were observed during the phasic period. The study's findings suggest that the brain is less sensitive to external stimuli during the phasic period than during the tonic period of REM sleep.