Linguistic hemispheric asymmetries from Awake state to REM sleep

A right hemisphere (RH) superiority, as compared to left hemisphere (LH), has been shown during REM sleep with respect to Wake and NREM states for RH tasks (e.g. 1). The question can be raised wether the increasing of RH asymmetry during REM is related to RH tasks only, or it is of more general nature. As matter of fact no variations in interhemispheric differences has been found in REM LH tasks (2, 3). These findings however might be dependent upon the type of linguistic tasks used: lateralized Letter Recognition Task, with both vowels and consonants (2); linguistic dichotic task in which a phonological code could be request (3). Both the tasks demand a strictly specific LH strategy. Aim of this research is to study whether hemispheric shiftings during REM sleep can be observed also with LH tasks more accessible to RH strategies, like a lateralized Consonant Recognition Task (CRT), in which stimuli can be processed also with a RH strategy (e.g. 4). METHOD. During one experimental night 12 male Ss (out of 16) - previously adapted to sleep Lab. - were tested in a CRT during Wake and upon awakenings from REM and NREM states. RESULTS AND CONCLUSIONS. ANOVA shows : 1) a main effect (p<.05) indicating a general LH superiority; 2) a slightly significant (p<.09) STATE x HEMISPHERE interaction showing a decrease of interhemispheric asymmetry upon awakening from REM state. Although preliminary and not yet completed this study supports the hypothesis that RH superiority in REM sleep may not be restricted to RH tasks.