title: Parietal EEG alpha suppression time of memory retrieval reflects memory load while the alpha power of memory maintenance is a composite of the visual process according to simultaneous and successive Sternberg memory tasks.
abstract: The present study investigated EEG alpha activity during visual Sternberg memory tasks using two different stimulus presentation modes to elucidate how the presentation mode affected parietal alpha activity. EEGs were recorded from 10 healthy adults during the Sternberg tasks in which memory items were presented simultaneously and successively. EEG power and suppression time (ST) in the alpha band (8-13Hz) were computed for the memory maintenance and retrieval phases. The alpha activity differed according to the presentation mode during the maintenance phase but not during the retrieval phase. Results indicated that parietal alpha power recorded during the maintenance phase did not reflect the memory load alone. In contrast, ST during the retrieval phase increased with the memory load for both presentation modes, indicating a serial memory scanning process, regardless of the presentation mode. These results indicate that there was a dynamic transition in the memory process from the maintenance phase, which was sensitive to external factors, toward the retrieval phase, during which the process converged on the sequential scanning process, the Sternberg task essentially required.
authors.affiliation: Graduate School of Engineering, Kyoto University, Kyoto Daigaku Katsura, Nishikyoku, Kyoto 615-8510, Japan; Japan Society for the Promotion of Science (JSPS), 5-3-1 Kojimachi, Chiyodaku, Tokyo 102-0083, Japan. Electronic address: sokuhata@kuee.kyoto-u.ac.jp.
authors.forename: Shiho
authors.initials: S
authors.lastname: Okuhata
authors.forename: Takuya
authors.initials: T
authors.lastname: Kusanagi
authors.forename: Tetsuo
authors.initials: T
authors.lastname: Kobayashi
mesh_terms: D000328:Adult; D000513:Alpha Rhythm; D005260:Female; D006801:Humans; D008297:Male; D008568:Memory / Q000502:physiology*; D010775:Photic Stimulation; D011930:Reaction Time; D014796:Visual Perception; D055815:Young Adult
keywords: Alpha suppression time; EEG; Parietal alpha power; Simultaneous and successive presentation; Sternberg memory task