Walking through a Maze Alters the Architecture of Sleep

Abstract

Human and animal studies imply that sleep is a critical period for consolidation of recent memories. Whereas the majority of researchers focussed on the procedural learning, the present human study concerns how storing of spatial information and episodic memory are linked to sleep stages. Two city mazes, a simple and a complex one, were created by means of a computer program. Local aspects of these mazes appeared as street scenes on a TV-screen. Our subjects sat in front of the screen and manoeuvered through the maze by the help of a three-button PC mouse. Thus, each subject took a 'mental walk' through an imaginary city. The task was to find various end-points and to find the way back to the starting point. Subjects of two experimental groups 'walked' through either the simple or complex city maze for eight hours. Afterwards the subjects slept in our laboratory, where their sleep stages could be measured polygraphically. Subjects who had explored the simple maze showed considerable alteration in sleep architecture. They remained significantly longer in sleep Stage 2 than subjects who had explored the complex maze. Moreover, with successful orientation in the simple maze sleep stages occurred aperiodically, whereas walking through the complex maze was associated with sleep stages in accordance with ultradian cycles, as observed in a control group. Compared to subjects of the control group who had experienced neither maze, the subjects of both experimental groups had significantly enhanced EEG sleep spindle activities. Alteration in temporal architecture of sleep and selective prolongation of sleep Stage 2 following spatial orientation point to a functional linkage between cognitive mapping of space and sleep Stage 2 with enhanced EEG spindle activity.

Elevated Sleep Spindle Density after Learning or after Retrieval in Rats

“…The learning-dependent activation of corticothalamic networks, expressed as an increase in spindle density during SWS, has been described in humans by several investigators (Meier-Koll et al, 1999;Fogel et al, 2002;Gais et al, 2002;Clemens et al, 2005). The present study is the first demonstration of the same phenomenon in rats and substantially extends findings in humans.…”

“…Sleep spindles, 12-15 Hz oscillations superimposed on slow waves , may promote neural plasticity underlying learning and memory (Steriade and Timofeev, 2003;Rosanova and Ulrich, 2005). Moreover, there is recent evidence for an increase in spindle density after verbal learning Clemens et al, 2005) or motor learning (Smith and MacNeill, 1994;Meier-Koll et al, 1999;Fogel et al, 2002).…”

Low acetylcholine during slow-wave sleep is critical for declarative memory consolidation

“…39 and 40) and can be explained when SWS is seen as a permissive factor for memory consolidation: SWS always occurs without regard to the actual amount of learning that has taken place. Accordingly, SWS does not increase after extensive declarative learning, and there is no increase in memory performance with increasing amounts of SWS in normal subjects (38,41). Only when large amounts of SWS are missing can impaired memory consolidation be seen (4,14).…”

Learned material content and acquisition level modulate cerebral reactivation during posttraining rapid-eye-movements sleep

“…A similar situation involves material so complex that its underlying structure cannot be extracted through practice. For instance, post-training modifications of the sleep architecture (in this case, increases of Stage 2 sleep duration) have been reported in humans after virtual maze exploration only when the complexity of the maze allowed subjects to learn their way and form a cognitive map (Meier-Koll et al, 1999).…”