Cognitive asymmetries after waking from REM and NONREM sleep: effects of delayed testing and handedness

The present paper describes two experiments designed to investigate cognitive asymmetry after awakening from REM and NONREM sleep as a function of time after the awakening and handedness. Two groups of 9 right-handed male subjects each participated in the first experiment. Subjects were awakened from REM and NONREM sleep and after 35 min (Group 1), or 75 min (Group 2), tested on a 6-test battery designed to measure cognitive asymmetry. In contrast to our previous findings in subjects tested within 1-2 min after the awakening who showed a significant sleep-stage dependent shift in cognitive asymmetry, the present results did not show significant differences in performance between the two awakening conditions for any of the groups. Two groups of 12 male and 12 female left-handed subjects participated in the second experiment. All subjects were tested within 1-2 min after the awakenings from REM and NONREM sleep on the same 6-test battery as in experiment 1. Also in contrast to our previous findings in right handers, left-handers did not show any consistent shifts in cognitive asymmetry after the awakenings.