William H. Obermeyer

Sleep and Behavior Problems in School-Aged Children

Objectives. The primary purposes of the present study were to survey the prevalence of sleep problems in school-aged children and to examine these associations with parental perception of sleep problems, medical history, and childhood psychopathology. Methods. Sleep and medical history questionnaires and the Child Behavior Checklist were administered to the parents of 472 children between ages 4 and 12 years receiving routine pediatric care from urban, rural, and suburban pediatric practices. Results. Although sleep problems were reported for 10.8% of the sample during the past 6 months, less than one half of the parents who identified sleep problems reported that they had discussed sleep with their childs pediatrician. The best predictor of current sleep problems was a history of sleep problems before age 2 years. Sleep problems such as snoring, tiredness during the day, and taking excessive time to fall asleep were very common, occurring at least 1 night per week in over 20% of the total sample. Factor analysis of the sleep problems questionnaire resulted in 5 sleep problem factors that accounted for 58.7% of the variance. Specific sleep problem factors include: parasomnias, enuresis/gags, tiredness, noisy sleep, and insomnia. Sleep problem factor scores were differentially associated with medical history variables and measures of childhood psychopathology. Children rated highly on parasomnias were more likely to have frequent falls and to display pica. Parasomnias and noisy sleep were inversely associated with socioeconomic status (SES). Children from lower SES families were rated higher on these factors than children from higher SES families. Enuresis/gags was the only sleep problem factor associated with age. Younger children scored higher on this factor. Duration of naps was highly correlated with age and with bed times during the week and weekends. As expected, younger children were more likely to nap for longer periods and to have earlier bed times. In addition, higher tiredness factor scores were associated with napping and with later bed times during the week and weekend. Boys were much more likely than were girls to have higher scores on enuresis/gags, and higher enuresis/gags scores were associated with an increased prevalence of trauma and falls. Bed times were not associated with any other sleep problem factor score. Children rated highly on tiredness were more likely to have a history of hospitalizations. Tiredness factor scores were strongly associated with the sleep practice of sharing a bed but not with sharing a room. Sharing a room was not associated with any sleep problem factor score. High scores on noisy sleep were associated with allergies, falls frequently, and with sharing a bed. Children with high scores on the insomnias were also more likely to display an increased prevalence of allergies. Conclusions. Parental perception of global sleep problems was surprisingly common in school-aged children receiving routine pediatric care. Parental reports of their childrens sleep problems may be a red flag for specific sleep problems and psychiatric, social, or medical problems. Sleep problems should be queried about during pediatric visits for school-aged children.

Migratory sleeplessness in the white-crowned sparrow (Zonotrichia leucophrys gambelii)

Twice a year, normally diurnal songbirds engage in long-distance nocturnal migrations between their wintering and breeding grounds. If and how songbirds sleep during these periods of increased activity has remained a mystery. We used a combination of electrophysiological recording and neurobehavioral testing to characterize seasonal changes in sleep and cognition in captive white-crowned sparrows (Zonotrichia leucophrys gambelii) across nonmigratory and migratory seasons. Compared to sparrows in a nonmigratory state, migratory sparrows spent approximately two-thirds less time sleeping. Despite reducing sleep during migration, accuracy and responding on a repeated-acquisition task remained at a high level in sparrows in a migratory state. This resistance to sleep loss during the prolonged migratory season is in direct contrast to the decline in accuracy and responding observed following as little as one night of experimenter-induced sleep restriction in the same birds during the nonmigratory season. Our results suggest that despite being adversely affected by sleep loss during the nonmigratory season, songbirds exhibit an unprecedented capacity to reduce sleep during migration for long periods of time without associated deficits in cognitive function. Understanding the mechanisms that mediate migratory sleeplessness may provide insights into the etiology of changes in sleep and behavior in seasonal mood disorders, as well as into the functions of sleep itself.

Sleep and mood disorders

Mood disorders are found in one-third to one-half of patients with chronic sleep problems. Likewise, most patients with mood disorders experience insomnia, but a minority obtain significantly increased amounts of sleep. Although mood disorders cause significant morbidity and mortality, they often go undiagnosed. Attention to sleep complaints could lead to better identification of mood disorders. Management of sleep problems in patients with mood disorders should focus on treating underlying mood disorders with attention to the nature of the sleep complaint. Patients with depression show characteristic abnormalities in sleep continuity, slow-wave sleep and REM sleep patterns. Differences in sleep patterns cannot reliably distinguish patients with depression from those with other psychiatric disorders, but sleep changes may provide a window on neurobiologieal abnormalities in depression.

Effects of drugs on sleep.

Many commonly prescribed medications and substances of abuse can have significant effects on sleep and wakefulness. Chronic use or abuse of certain drugs may lead to the development of substance-related sleep disorders. Primary sleep disorders, such as apnea, periodic movement disorders, and parasomnias, may be exacerbated by various drugs. This article summarizes the effects of widely used medications and recreational drugs on sleep.

EEG alpha power and alpha power asymmetry in sleep and wakefulness

Asymmetry of waking electroencephalography (EEG) alpha power in frontal regions has been correlated with waking emotional reactivity and the emotional content of dream reports. Little is known regarding alpha asymmetry during sleep. The present study was performed to compare alpha power and alpha power asymmetry in various brain regions across states of sleep and wakefulness. Waking and sleep EEG were recorded in a group of patients undergoing polysomnographic evaluation for possible sleep disorders. Alpha EEG asymmetry in frontal and temporal regions was significantly correlated in waking versus sleep, particularly during rapid eye movement (REM) sleep. These results suggest that patterns of frontal alpha asymmetry are stable across sleep and waking and may be related to emotional reactivity during dreaming. During sleep, alpha power was highest during slow-wave sleep and lowest during REM sleep. Implications of these data for understanding the functional significance of alpha power during waking and sleeping are considered.

Effects of amygdala lesions on sleep in rhesus monkeys

The amygdala is important in processing emotion and in the acquisition and expression of fear and anxiety. It also appears to be involved in the regulation of sleep and wakefulness. The purpose of this study was to assess the effects of, fiber-sparing lesions of the amygdala on sleep in rhesus monkeys (Macaca mulatta). We recorded sleep from 18 age-matched male rhesus monkeys, 11 of which had previously received ibotenic acid lesions of the amygdala and seven of which were normal controls. Surface electrodes for sleep recording were attached and the subjects were seated in a restraint chair (to which they had been adapted) for the nocturnal sleep period. Despite adaptation, control animals had sleep patterns characterized by frequent arousals. Sleep was least disrupted in animals with large bilateral lesions of the amygdala. They had more sleep and a higher proportion of rapid-eye-movement (REM) sleep than did either animals with smaller lesions or control animals. Based on these results, it seems likely that, in the primate, the amygdala plays a role in sleep regulation and may be important in mediating the effects of emotions/stress on sleep. These findings may also be relevant to understanding sleep disturbances associated with psychopathology.

Fos immunoreactivity in rat subcortical visual shell in response to illuminance changes

Immediate early gene expression has been used frequently as a marker of activity in the circadian visual system. Recent evidence suggests that the pretectum participates in orchestrating sleep and circadian responses to light. Lesions of the pretectum eliminate dark shift-induced rapid eye movement sleep triggering in albino rats, and compromise circadian phase shifts in hamsters. We hypothesized that regions of the pretectum respond to light with robust and region-specific Fos activation, similar to the suprachiasmatic nucleus and intergeniculate leaflet. We used Fos expression, the protein product of the immediate early gene c-fos, as a functional marker to measure the responses of neurons following acute lighting changes. Rats maintained on a 12:12 light-dark cycle were subjected to a shift from light-to-dark or from dark-to-light at midday (Zeitgeber time 6) or midnight (Zeitgeber time 18). Fos expression was visualized with immunocytochemistry and quantified with an automated scoring system. We found three regions in the pretectum (the olivary pretectal nucleus, posterior limitans, and a region homologous to the hamster commissural pretectal nucleus), and two regions in the lateral geniculate complex (the intergeniculate leaflet and ventral lateral geniculate nucleus) that demonstrated significant Fos activation in response to light. Furthermore, the olivary pretectal nucleus, the posterior limitans, and the ventral lateral geniculate nucleus showed preferential Fos activation after acute light onset rather than following chronic exposure to light at midday, whereas at midnight these nuclei showed Fos activation following both chronic light exposure and acute light onset. Given the extensive anatomical connections between pretectal nuclei and other nuclei in the subcortical visual shell, as well as with centers for sleep and arousal, it is highly plausible that these pretectal nuclei integrate information about changes in illuminance, and aid in the coordination of acute behavioral responses to light.

Increased Basal REM Sleep But No Difference in Dark Induction or Light Suppression of REM Sleep in Flinders Rats with Cholinergic Supersensitivity

Increased cholinergic sensitivity in the central nervous system has been postulated to account for some of the neuroendocrine abnormalities and sleep disturbances seen in human depressives. The Flinders Sensitive Line (FSL) rats, which exhibit increased sensitivity to cholinergic agents, have been shown to have REM sleep patterns similar to those seen in depressives, including shorter REM sleep latency and increased daily percentage of REM sleep.We studied the response of FSL and control rats to brief dark pulses administered during the normal light period (which are known to stimulate REM sleep in albino rats) and to brief light pulses during the normal dark period (which suppress REM sleep in albino rats) to determine whether these responses are affected by central cholinergic hypersensitivity. FSL rats showed REM sleep patterns indistinguishable from controls during light or dark pulses, which does not support the primary involvement of cholinergic systems in this mechanism of REM sleep regulation.We also examined REM and non-REM (NREM) sleep patterns in FSL rats and their controls to determine whether they show sleep continuity disturbances or decreased sleep intensity as seen in depression. In agreement with an earlier study, we found that FSL rats had more daily REM sleep and accumulated less NREM sleep between REM bouts than controls. Duration of NREM sleep bouts, total daily NREM sleep time, and EEG amplitude of NREM sleep did not differ between FSL and control rats, suggesting that the cholinergic abnormalities in FSL rats do not produce substantial NREM sleep changes.

The pretectum mediates rapid eye movement sleep regulation by light.

A variety of sensory stimuli (e.g., visual, auditory, and thermal) are known to induce rapid eye movement (REM) sleep in mammals. Studies have examined the induction of REM sleep in albino rats by light-to-dark transitions, a phenomenon referred to as REM sleep triggering. Recent research has demonstrated that aspiration lesions of the superior colliculus (SC) and pretectal area attenuated REM sleep triggering. To define more specifically the area or areas involved in mediating REM sleep responses to changes in illumination, fiber-sparing neurotoxic lesions were made to the pretectum (PT) or the SC. Lesions of the PT attenuated REM sleep triggering, whereas lesions of the SC did not. Thus, the role of the PT may be expanded to include the regulation of REM sleep in response to photic stimulation in albino rats. These findings provide a paradigm in which to study mechanisms of REM sleep generation and the effects of light on behavioral state.

Sleep deprivation in the pigeon using the Disk-Over-Water method

A well-defined sleep deprivation (SD) syndrome has been observed in studies with rats under conditions of severe sleep loss on the Disk-Over-Water (DOW) apparatus. Observation of the sleep deprivation syndrome across taxa would assist in the elucidation of the function of sleep. In the present study, the effects of total sleep deprivation were assessed in pigeons, a biologically relevant choice given that birds are the only non-mammalian taxon known to exhibit unequivocal rapid-eye-movement (REM) sleep and non-REM (NREM) sleep. Pigeons were deprived of sleep for 24-29 days on the DOW by rotating the disk and requiring them to walk whenever sleep was initiated. Control (C) birds were also housed on the DOW and required to walk only when the deprived (D) birds were required to walk due to sleep initiation. NREM and REM sleep amounts were reduced from baseline during the deprivation for both D and C birds, although D birds obtained less NREM sleep than controls. Across the deprivation, D birds had their total sleep reduced by 54% of baseline (scored in 4 s epochs), whereas previous studies in rats on the DOW reported total sleep reduction of as much as 91% (scored in 30 s epochs). Pigeons proved to be more resistant to sleep deprivation by the DOW method and were much more difficult to deprive over the course of the experiment. Overall, the pigeons showed recovery sleep patterns similar to those seen in rats; i.e., rebound sleep during recovery was disproportionately composed of REM sleep. They did not, however, show the obvious external physical signs of the SD syndrome nor the large metabolic and thermoregulatory changes associated with the syndrome. The DOW method was thus effective in producing sleep loss in the pigeon, but was not as effective as it is in rats. The absence of the full SD syndrome is discussed in the context of limitations of the DOW apparatus and the possibility of species-specific adaptations that birds may possess to withstand or adapt to conditions of limited sleep opportunity.