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Right hemisphere superiority for the night and left hemisphere superiority for the day: a re-patterning of laterality across wake-sleep-wake states.
No full textDuring the sleep onset period (SOP), there is a state-specific relative advantage of the right hemisphere (RH). This superiority could either be due to the ability of the RH when operating at levels of reduced arousal, as suggested by its superiority in sustaining vigilance, or it could depend on a more pronounced homeostatic deactivation of the left hemisphere (LH). To evaluate whether variations of lateralization from wake to sleep are consistent with one of these two hypotheses, we considered a finger tapping task (FTT) bimanually performed during two wakeful conditions, during the SOP, upon experimental awakenings from stage 2 and REM sleep in the first and in the second part of the night, and upon morning awakening. The RH advantage in sustaining vigilance would be supported if the relative RH advantage was present throughout the sleep period. Finding that the repatterning of hemispheric asymmetry is present and/or prominent in the first part of the night would support the homeostatic hypothesis, i.e. when the homeostatic process is more pronounced. Results from 16 subjects revealed a significant superiority of the LH during the two wakeful conditions. At sleep onset, a clear reversal of dominance was observed and it was followed by a steady RH superiority upon both REM and NREM sleep awakenings, and upon the morning sleep–wake transition. Therefore, performance in a FTT reveals a repatterning of laterality across wake–sleep–wake states. These results are interpreted as consistent with the hypothesis concerning an advantage of the RH in sustaining vigilance
The sleep-wake transition: hemispheric asymmetries upon morning awakening evaluated by a finger tapping task.
No full textLaterality of sleep onset process: which hemisphere goes to sleep first?
No full textThis study aims to assess whether the hemispheric asymmetry inversion observed in the wake-sleep transition can also be revealed by the latency of inter tapping intervals 2.5 s for each hand and the latency of theta burst 2.5 s in symmetrical loci of the two hemispheres during the sleep onset process. Data collected from 16 right-handed subjects showed a hemispheric asymmetry in the sleep onset latency with both behavioural and EEG indices. For the first time, a hemispheric asymmetry in the sleep onset latency was found considering a visual analysis of EEG. Results suggest that the hemispheric pattern found during sleep onset can be considered a steady characteristic of the transition from wake to sleep, relatively independent of homeostatic and time of night effects. These results are interpreted as being consistent with the hypothesis concerning an advantage of the right hemisphere in sustaining vigilance
Transizione sonno-veglia: asimmetrie motorie al risveglio valutate mediante un compito di tapping.
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The postawakening testing technique in the investigation of cognitive asymmetries during sleep
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