Partial sleep in the context of augmentation of brain function

Abstract

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.

Keywords: cerebral cortex; local sleep; sleep function; slow wave sleep; visceral control.

Figure 1

Rhythmic stimulation by the optimal visual stimulus during wakefulness evokes sleep like slow wave activity in the cat visual cortex. The rows: (A) vertical component of eye movements which helps to distinguish sleep (upward deviation) from wakefulness (downward deviation); (B) general EEG recorded between electrodes over temporal and frontal cortical areas of the cat; (C) local field potentials (local EEG) recorded between two tungsten microelectrodes located 300 μm one from another within the cortical visual area V1; (D) power spectrum of the local EEG presented above in panel C. All parameters were collected during SWS (left column), during passive wakefulness (middle column), and during the procedure of “sleep EEG imitation” by visual stimulation in wakefulness, which produced strong excitation of the cortical neurons recorded by the microelectrodes (right column). Technical details of the study in Pigarev et al. (2013).

Figure 2

Periodic optimal somatic stimulation during wakefulness evokes sleep like slow wave activity in the cat somatosensory cortex. The rows: (A) vertical component of eye movements which helps to distinguish sleep (upward deviation) from wakefulness (downward deviation); (B) general EEG recorded between electrodes over temporal and frontal cortical areas of the cat; (C) local field potentials (local EEG) recorded between two tungsten microelectrodes located 300 mm one from another within the cortical somatosensory area 5; (D) power spectrum of the local EEG presented above in panel C. All parameters were collected during SWS (left column), during passive wakefulness (middle column), and during the procedure of “sleep EEG imitation” by visual stimulation in wakefulness, which produced strong excitation of the cortical neurons recorded by the microelectrodes (right column). Technical details of the study in Pigarev et al. (2013).

Figure 3

Responses of neurons in the cat cortical visual area V1 (A) and somatosensory area 5 (B) to intraperitoneal electrical stimulation delivered in sleep and in wakefulness. Responses presented as rasters where every line corresponds to single stimulation trial. Dots represent single spikes. Below are averaged histograms. Vertical red line–moment of intraperitoneal stimulation. n—number of averaged trials. Technical details of the study in Pigarev (1994).

Figure 4

Population response of 61 neurons (615 trials) in monkey’s cortical visual area V4 to magnetic stimulation of stomach during SWS. Vertical red line–moment of stimulation. Horizontal green line indicate mean background firing rate before stimulation taken as 100%. Technical details of the study in Pigarev et al. (2008).

Figure 5

Episode of SWS. (A) Spectrogram of the cat cortical EEG. Yellow color indicates higher power. (B) Myoelectrical activity of stomach. Technical details of the study in Pigarev et al. (2013).

Figure 6

Neuronal activity in the cat primary visual cortex synchronized with respiration during SWS. (A) Multiunit activity; (B) local field potentials (local EEG); (C) nasal air flow in relative units. Technical details of the study in Pigarev et al. (2013).