A Selective Effect of Partial Sleep Deprivation on Metaphor Generation Among Healthy Young Adults.

Partial sleep deprivation (SD), a common phenomenon in modern life, is known to impair cognitive and linguistic processes. This study investigates its selective effect on metaphor generation, differentiating between conventional and novel metaphors. Twenty-five healthy young adults underwent two sessions involving either regular sleep or partial SD conditions. Participants completed tasks evaluating metaphor generation, cognitive flexibility (Stroop Test), and executive function (Wisconsin Card Sorting Test). Results revealed that partial SD increased the production of conventional metaphors, associated with bottom-up processes and default mode network (DMN) activation. However, it did not significantly affect novel metaphor generation, which relies on top-down cognitive control and frontoparietal network (FPN) activity. Furthermore, Stroop Test findings showed slower reaction times under incongruent conditions after partial SD, indicating reduced cognitive control. These results suggest that partial SD selectively impairs top-down processes while enhancing bottom-up retrieval, leading to a shift in metaphor generation patterns. This research highlights the distinct neural mechanisms underlying different types of metaphor generation and their differential sensitivity to partial SD, providing theoretical and psycholinguistic insights into the cognitive effects of SD.