Abstract
Despite intensive study, the data regarding functional role of specific brain regions in the working memory processes still remain controversial. The study was aimed to determine the activation of cerebral cortex regions at different stages of the working memory task (information encoding, maintenance and retrieval). Functional magnetic resonance imaging (fMRI) with the modified Sternberg task was applied to 19 healthy volunteers. The objective of the task was to memorize and retain in memory the sequence of 7 letters with the subsequent comparison of one letter with the sequence. Activation was analyzed during three periods of the task compared to the rest period, as well as temporal dynamics of changes in BOLD signal intensity in three regions: left dorsolateral prefrontal, left posterior parietal and left occipital cortex. According to the results, significant activation of the regions in prefrontal and posterior parietal cortex was observed during all periods of the task (p < 0.05), but there were changes in its localization and lateralization. The activation pattern during the maintenance period corresponded to the fronto-parietal control network components. According to the analysis of temporal dynamics of changes in BOLD signal intensity, the most prominent activation of the dorsolateral prefrontal cortex and parietal cortex was observed in the end of the encoding period, during the maintenance period and in the beginning of the retrieval period, which confirmed the role of those areas in the working memory processes. The maximum of occipital cortex activation was observed during encoding period. The study confirmed the functional role of the dorsolateral prefrontal cortex and posterior parietal cortex in the working memory mechanisms during all stages of the Sternberg task.
Highlights
Author contribution: Bakulin IS, Fedorov MV, Gnedovskaya EV, Suponeva NA, Piradov MA — study planning and design; Bakulin IS, Zabirova AH — literature analysis; Bakulin IS, Poydasheva AG — data acquisition; Zabirova AH, Kopnin PN, Sinitsyn DO — data analysis; Bakulin IS, Zabirova AH, Sinitsyn DO, Fedorov MV, Gnedovskaya EV, Suponeva NA, Piradov MA — data interpretation; Bakulin IS, Zabirova AH — manuscript draft preparation; Kopnin PN, Sinitsyn DO, Poydasheva AG, Fedorov MV, Gnedovskaya EV, Suponeva NA, Piradov MA — manuscript draft editing; all the authors — final version of the article preparation
The study was performed as a part of the project “Effects of high-frequency repetitive transcranial magnetic stimulation over the left dorsolateral prefrontal cortex on working memory in healthy volunteers”
During the maintenance period significant activation was found in the medial parts of the frontal lobes, prefrontal cortex, parietal lobe
Summary
Author contribution: Bakulin IS, Fedorov MV, Gnedovskaya EV, Suponeva NA, Piradov MA — study planning and design; Bakulin IS, Zabirova AH — literature analysis; Bakulin IS, Poydasheva AG — data acquisition; Zabirova AH, Kopnin PN, Sinitsyn DO — data analysis; Bakulin IS, Zabirova AH, Sinitsyn DO, Fedorov MV, Gnedovskaya EV, Suponeva NA, Piradov MA — data interpretation; Bakulin IS, Zabirova AH — manuscript draft preparation; Kopnin PN, Sinitsyn DO, Poydasheva AG, Fedorov MV, Gnedovskaya EV, Suponeva NA, Piradov MA — manuscript draft editing; all the authors — final version of the article preparation. На протяжении всех периодов задачи наблюдали статистически значимую активацию участков ПФК и задней теменной коры (р < 0,05), но с изменением их локализации и латерализации. По результатам анализа изменения интенсивности BOLD-сигнала наиболее выраженную активацию ДЛПФК и теменной коры наблюдали в конце периода запечатления, периоде удержания и начале периода извлечения, что подтверждает роль данных областей в процессах РП. Данное исследование подтверждает функциональное значение ДЛПФК и задней теменной коры для процессов РП на всех этапах выполнения задачи Стернберга. One of the brain areas, most investigated in context of working memory, is the dorsolateral prefrontal cortex. The persistent neural activity during the maintenance period of the working memory task was firstly observed in the prefrontal cortex of primates [4]. A number of studies confirmed the importance of the persistent neural activity in prefrontal cortex. The temporary inactivation of the prefrontal cortex led to a more pronounced working memory decline than inactivation of the posterior parietal cortex [6]
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