Sleep and the Control of Visceral Functions

Visceral theory of sleep and origins of mental disorders

Visceral theory of sleep states that the same brain neurons, which process external information in wakefulness, during sleep switch to the processing of internal information coming from various visceral systems. Here we hypothesize that a failure in the commutation of exteroceptive and interoceptive information flows in the brain can manifest itself as a mental illness.

Actigraphically Measured Sleep-Wake Behavior After Mild Traumatic Brain Injury: A Case-Control Study

OBJECTIVE

To characterize and compare the sleep-wake behavior of individuals following a mild traumatic brain injury (mTBI) with that of noninjured healthy controls.

SETTING

Community.

PARTICIPANTS

Fourteen participants with a recent mTBI (Mage = 28.07; SD = 10.45; n = 10 females) and 34 noninjured controls (Mage = 23.70; SD = 7.30; n = 31 females).

DESIGN

Cross-sectional.

MAIN MEASURES

Battery of subjective sleep measures and 14 days of sleep-wake monitoring via actigraphy (objective measurement) and concurrent daily sleep diary.

RESULTS

Participants who had sustained an mTBI self-reported significantly higher sleep-related impairment, poorer nightly sleep quality, and more frequently met criteria for clinical insomnia, compared with controls (d = 0.76-1.11, large effects). The only significant between-group difference on objective sleep metrics occurred on sleep timing. On average, people with a recent history of mTBI fell asleep and woke approximately 1 hour earlier than did the controls (d = 0.62-0.92, medium to large effects).

CONCLUSION

Participants with a history of mTBI had several subjective sleep complaints but relatively few objective sleep changes with the exception of earlier sleep timing. Future research is needed to understand the clinical significance of these findings and how these symptoms can be alleviated. Interventions addressing subjective sleep complaints (eg, cognitive behavior therapy for insomnia) should be tested in this population.

The state of sleep and the current brain paradigm

Up to the present time cerebral cortex was considered as substrate for realization of the highest psychical functions including consciousness. Cortical sensory areas were regarded as structures specialized for processing of information coming from one particular modality (visual, auditory, somatosensory, and so on). However, studies of cortical activity in sleep-wake cycle demonstrated that during sleep the same neurons in the same cortical areas switch to processing of signals coming from the various visceral systems. After awakening these visceral responses disappear and the neurons return to processing of the information coming from the exteroreceptors. These observations indicate that most likely cortical areas are universal processors, which perform particular operations with incoming information independent of its origin. During wakefulness, results of the information processing on the cortical level should be directed to structures connected with organization of behavior and consciousness, while during sleep cortical outputs should be redirected to structures performing integration of the visceral information. Thus, results of sleep studies indicate that current brain paradigm should be changed.

Partial sleep in the context of augmentation of brain function

Inability to solve complex problems or errors in decision making is often attributed to poor brain processing, and raises the issue of brain augmentation. Investigation of neuronal activity in the cerebral cortex in the sleep-wake cycle offers insights into the mechanisms underlying the reduction in mental abilities for complex problem solving. Some cortical areas may transit into a sleep state while an organism is still awake. Such local sleep would reduce behavioral ability in the tasks for which the sleeping areas are crucial. The studies of this phenomenon have indicated that local sleep develops in high order cortical areas. This is why complex problem solving is mostly affected by local sleep, and prevention of local sleep might be a potential way of augmentation of brain function. For this approach to brain augmentation not to entail negative consequences for the organism, it is necessary to understand the functional role of sleep. Our studies have given an unexpected answer to this question. It was shown that cortical areas that process signals from extero- and proprioreceptors during wakefulness, switch to the processing of interoceptive information during sleep. It became clear that during sleep all "computational power" of the brain is directed to the restoration of the vital functions of internal organs. These results explain the logic behind the initiation of total and local sleep. Indeed, a mismatch between the current parameters of any visceral system and the genetically determined normal range would provide the feeling of tiredness, or sleep pressure. If an environmental situation allows falling asleep, the organism would transit to a normal total sleep in all cortical areas. However, if it is impossible to go to sleep immediately, partial sleep may develop in some cortical areas in the still behaviorally awake organism. This local sleep may reduce both the "intellectual power" and the restorative function of sleep for visceral organs.