Walking through a maze alters the architecture of sleep

Human and animal studies imply that sleep is a critical period for consolid ation of recent memories. Whereas the majority of researchers focussed on t he procedural learning, the present human study concerns how storing of spa tial information and episodic memory are linked to sleep stages. Two city m azes, a simple and a complex one, were created by means of a computer progr am. 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 wal k' through an imaginary city. The task was to find various end-points and t o find the way back to the starting point. Subjects of two experimental gro ups '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 ma ze showed considerable alteration in sleep architecture. They remained sign ificantly longer in sleep Stage 2 than subjects who had explored the comple x maze. Moreover, with successful orientation in the simple maze sleep stag es occurred aperiodically, whereas walking through the complex maze was ass ociated with sleep stages in accordance with ultradian cycles, as observed in a control group. Compared to subjects of the control group who had exper ienced neither maze, the subjects of both experimental groups had significa ntly enhanced EEG sleep spindle activities. Alteration in temporal architec ture of sleep and selective prolongation of sleep Stage 2 following spatial orientation point to a functional linkage between cognitive mapping of spa ce and sleep Stage 2 with enhanced EEG spindle activity.