Covert Waking Brain Activity Reveals Instantaneous Sleep Depth

The neural correlates of the wake-sleep continuum remain incompletely understood, limiting the development of adaptive drug delivery systems for promoting sleep maintenance. The most useful measure for resolving early positions along this continuum is the alpha oscillation, an 8–13 Hz electroencephalographic rhythm prominent over posterior scalp locations. The brain activation signature of wakefulness, alpha expression discloses immediate levels of alertness and dissipates in concert with fading awareness as sleep begins. This brain activity pattern, however, is largely ignored once sleep begins. Here we show that the intensity of spectral power in the alpha band actually continues to disclose instantaneous responsiveness to noise—a measure of sleep depth—throughout a night of sleep. By systematically challenging sleep with realistic and varied acoustic disruption, we found that sleepers exhibited markedly greater sensitivity to sounds during moments of elevated alpha expression. This result demonstrates that alpha power is not a binary marker of the transition between sleep and wakefulness, but carries rich information about immediate sleep stability. Further, it shows that an empirical and ecologically relevant form of sleep depth is revealed in real-time by EEG spectral content in the alpha band, a measure that affords prediction on the order of minutes. This signal, which transcends the boundaries of classical sleep stages, could potentially be used for real-time feedback to novel, adaptive drug delivery systems for inducing sleep

Coping and injury attribution in head-injured adults

The purpose of this study was to examine the coping styles, beliefs, and symptoms of head-injured adults during long term recovery. Twenty-eight head-injured and thirty-two control subjects suffering from non-neurological illnesses or injuries participated. Subjects completed the Ways of Coping Questionnaire and two questionnaires developed for this study: the "Why Me?" Questionnaire assessed subjects' causal attributions and beliefs about responsibility and the Head-Injury Symptom List provided self-report of the severity of symptoms of head-injury. The coping and belief profiles of the two groups were compared. Head-injured subjects were more likely to place responsibility for their injury on others and to undertake personal efforts to effect their recovery. Various relations between injury attributions and coping styles were obtained. Among both head-injured and control subjects those who endorsed beliefs of retribution were more likely to cope by wishing they could change their situation. Responses to the Head-Injury Symptom List identified tiredness as the most pervasive symptom. Greater symptomatology was related both to a coping style characterized by lack of ability or willingness to engage in social activity or to seek social support and to beliefs that the injury had occurred to serve a meaningful purpose. Consistent with these quantitative results, interviews with head-injured subjects revealed themes of both loss and enhancement. A majority compared their recovery favorably with that of other individuals. In support of cognitive coping theory, this research demonstrates the feasibility of studying the coping capacities of head-injured individuals and shows that they have distinctive coping styles and beliefs which are related to each other. This knowledge should aid those trying to support the recovery of head-injured individuals by adding to the framework upon which interventions are based

Spontaneous brain rhythms predict sleep stability in the face of noise

SummaryQuality sleep is an essential part of health and well-being. Yet fractured sleep is disturbingly prevalent in our society, partly due to insults from a variety of noises [1]. Common experience suggests that this fragility of sleep is highly variable between people, but it is unclear what mechanisms drive these differences. Here we show that it is possible to predict an individual's ability to maintain sleep in the face of sound using spontaneous brain rhythms from electroencephalography (EEG). The sleep spindle is a thalamocortical rhythm manifested on the EEG as a brief 11–15 Hz oscillation and is thought to be capable of modulating the influence of external stimuli [2]. Its rate of occurrence, while variable across people, is stable across nights [3]. We found that individuals who generated more sleep spindles during a quiet night of sleep went on to exhibit higher tolerance for noise during a subsequent, noisy night of sleep. This result shows that the sleeping brain's spontaneous activity heralds individual resilience to disruptive stimuli. Our finding sets the stage for future studies that attempt to augment spindle production to enhance sleep continuity when confronted with noise