Reseach On Dynamic Mechanism Of Brain During Retention Period Of Working Memory

Working memory is a kind of memory system in which information can be shortly stored and frequently updated as well as quickly extracted. Being a transfer unit for information, retention period connects coding and extraction periods, which separately represent input and output of information. Brain mechanism of retention period is always a key field in working memory research even neural cognition process research of human. Duration of the retention period is generally defined as 10 s to 12 s, but most of previous studies were confined to how brain works within first 4s of the retention interval, lacking for the study of later period. There’s also research regarding a relatively long retention period as a whole to analysis, ignoring the dynamic changing process.This experiment uses the traditional working memory paradigm, the Sternberg paradigm, designs the same type of tasks in three workload conditions, chooses the alpha and theta band to explore the dynamic changing during the retention period of working memory according to the memory load effect. We separates the retention period into four stages. A spectral analysis and brain network analysis is separately studied within each stage of retention period and concentrated upon the theta and alpha band. The spectral power and coefficient of network are adopted in researching of memory load effect.This paper contains three main sections:Section one: Materials and methods. A detailed procedure including subjects, tasks, data acquisition and data analysis is given. The programs applied in this experiment and the Sternberg paradigm is also introduced.Section two: Results. This section presents the results of dynamic changing during retention period of working memory from three concepts, i.e. behavioral research, spectral analysis and brain network analysis. The memory load effect is explored using spectral power and coefficient of network. Confirm the brain mechanism during retention period being a dynamic process by observing changes of memory load effect within four stages.Section three: Discussion. Discussion and interpretation of the results are presented after reference and comparison with some previous memory-related studies. The discussion and interpretation include the mechanism of the alpha and theta oscillation, resource allocation of working memory related alpha and theta activity, demonstrations in brain network, influences of other working memory related neural process, such as keeping attention and central execution system, on the alpha and theta oscillation, etc.Primary results of the experiment:The theta band presents a positive load effect on the frontal cortex, whereas posterior positive load effect in the alpha band;Brain network shows an obviously change during four stages of retention period of working memory;As the retention period proceeding, memory load effect on the alpha and theta band changes according to different mode.