Correlates of adaptation to the sleep laboratory. Behavior, sleep organization, quantitative EEG.

The present study aims at establishing to what extent adaptation phenomena should be taken into consideration for the definition of an independent baseline in sleep research. To this purpose we have studied: (1) a standard battery of neuropsychological test evaluating performance, subjective assessments of moods and sleep quality; (2) classical sleep parameters; (3) data derived from quantitative analysis of sleep EEG. 19 young male volunteers have been recorded for consecutive nights; 7 of them underwent the recordings for 3, 8 for 6 and 4 for 10 nights. Results can be summarized as follows: (A) both interindividual and intraindividual variability show a progressively decreasing trend toward homogeneity for most of the explored parameters; (B) steady state is reached in different times for different groups of parameters; (C) an adequate group homogeneity was achieved from the 5th night onwards. Implications of these data in sleep studies, namely in sleep active drug research are discussed.