The present study applies encephalography (EEG) to examine the neural nature of procrastination. Concerning the development of the paradigm of modern EEG research, we assume the relationship of procrastination with a separate memory subsystem, which stores information about life events and intentions for future actions. This type of memory has been called prospective memory instead of classical retrospective memory (Ericson, 2017). In developing this study, we suggest different tasks combining two types of linguistic stimuli: task giving an access to working memory and task activating prospective memory. We suggested two tasks to the subjects simultaneously. Moreover, prospective stimuli included perceptual stimulus (Raskin et al., 2011) and semantic stimulus (West, 2008; Crystal & Wilson, 2015). The current study aims to is to examine the brain activity of individuals with different levels of procrastination. The study applies EEG data analysis with different levels of linguistic stimuli complexity (letter and semantic word), allowing to change the cognitive load and register the electrical activity of the cerebral cortex while performing tasks with two different stimuli: perceptual and semantic.
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The electrodes were placed according to the international system of 10/20% in 21 symmetrical points of the left and right hemispheres of the brain. The experiment applies referent ear electrodes A1 and A2, and additional referent electrodes N and Ref. During the Fourier transform, the epoch of analysis was 500 ms. Analog signal sampling frequency – 2 ms; input resistance for in-phase signal – more than 100 Mohm. High-frequency filters are set to 50 Hz, low – 0.1 Hz – limits of possible relative error when measuring voltage and time intervals of electroencephalographic signals – ± 5%. The study applies ICA analysis to screen EEG artefacts. Subsequently, the ISA components were filtered with the artefact signal and composition of non-artefact ISA, resulting in general patterns of EEG. In the cases that artefact activity could not be filtered by ISA treatment, artefact EEG segments were manually excised from the EEG. The study registered electrical activity of the cerebral cortex while performing test tasks of two types, introducing perceptual and semantic stimuli. 1. Prospective memory test using a perceptual stimulus. We instructed the subject to indicate the presence/absence of a semantic pair by pressing the "left" key in case of a semantic pair or "right" in its absence (a task for the use of working memory). If a word starts with a capital letter appearing on the screen, the subject must press the "down" key (prospective memory task). After pressing the appropriate key, the subject received feedback on the correctness of choice. The total duration of the test was 15 min and involved sorting 200 words, of which 20 were with capital letters. To avoid an automatic response by the subjects, the interval of presentation of stimuli ranged from 1 to 1.5 s, the duration of the demonstration of words – 2 s. 2. Test for prospective memory using a semantic stimulus. We asked the subjects to indicate the presence/absence of a semantic pair with the demonstrated word by pressing the "left" key in the case of semantic pair or "right" in its absence (a task for the use of working memory). If a word denoting animal appeared on the screen, the subject had to press the "down" key (prospective memory task). After pressing the appropriate key, the subject received feedback on the correctness of choice. The total duration of the test was 15 min and involved the sorting of 200 words, 20 of which contained the names of animals. Although to avoid an automatic response by the subjects, the interval of presentation of stimuli ranged from 1 to 1.5 s, the duration of the demonstration of words was 2 s.