Effects of sleep reduction on the phonological and visuospatial components of working memory

Abstract

Sleep reduction impairs the performance of many tasks, so it may affect a basic cognitive process, such as working memory, crucial for the execution of a broad range of activities. Working memory has two storage components: a phonological and a visuospatial component. The objective of this study was to analyze the effects of sleep reduction for 5 days on the storage components of working memory. Thirteen undergraduate students (18.77±2.20 years of age), 5 men and 8 women, responded two N-Back tasks (auditory and visual), with three sections each (0-Back, 1-Back, and 2-Back). These tasks were performed at 13:00 h under the following conditions: before sleep reduction (control; C); on the first (SR1), fourth (SR4), and fifth (SR5) days of sleep reduction (4 h of sleep per night); and one day after they slept freely (recovery, R). Sleep reduction produced a decrement in accuracy on the auditory 2-Back section the fifth day of sleep reduction (C=87.86±13.35%; SR5=74.76±16.37%; F=14.57, p<0.01). In the visual 2-Back section accuracy decreased (C=88.10±9.95%; SR1=82.45±11.57%; SR5=77.76±14.14%; F=10.80, p<0.05), and reaction time increased (C=810.02±173.96 ms; SR1=913.51±172.25 ms; SR5=874.78±172.27 ms; F=10.80, p<0.05) on the first and fifth day of sleep reduction. In conclusion, five days of sleep reduction produces a decrease in the phonological and visuospatial storage components of working memory, which may interfere with processing verbal information and solving problems that require spatial analysis.

Keywords: Phonological storage; Sleep reduction; Visuospatial storage; Working memory.

Fig. 1

Auditory N-Back task. This task consists of presenting a series of auditory stimuli (syllables). It includes three sections: 0-Back, 1-Back, and 2-Back. During the 0-Back section, the participant must indicate whether each syllable presented is the same as the syllable presented at the beginning of the section. During the 1-Back section, the participant must indicate whether each syllable presented is the same as the one presented immediately prior. During the 2-Back section, the participant must indicate whether each syllable presented is the same as the syllable that appeared two events prior.

Fig. 2

Visual N-Back task. This task consists of presenting a series of visual stimuli (black boxes) in a certain location on the screen. This task has three sections: 0-Back, 1-Back, and 2-Back. During the 0-Back section, the participant must indicate whether the location of each box presented is the same as the position of the box presented at the beginning of the section. During the 1-Back section, the participant must indicate whether the location of each box presented is the same as the location of the box presented immediately prior. During the 2-Back section, the participant must indicate whether the location of each box is the same as the location of the box presented two events prior.