| dc.description.abstract | With aging, the issue and emphasis on cognitive decline among human population has become more serious. Research addressing the relationship between aging and cognitive function has also been receiving greater attention recently. Among all the cognitive functions, working memory is considered to be one of the most sensitive ones to aging. In prior studies, the complex internal structure of working memory and the experimental assignments and experimental settings used by the researchers are different, making the research results diverse and complex. In summary, working memory tasks that emphasize the ability to perform processing have a greater age effect. However, in order to better comprehend the brain mechanism of working memory decline, researchers used electroencephalography (EEG) in the study and proposed that neural oscillations and their synchronization play an important role in cognitive functions that require rapid formation of neural assemblies, such as visual working memory. Alpha power is believed to be related to the performance of focusing on external information and maintaining memory in the execution of working memory tasks. Past studies have shown that the alpha power before stimulation is related to the subsequent performance, and the alpha suppression in the encoding phase is also related to the ability to process stimuli, but there is currently no systematic literature on the relationship between aging of working memory and alpha power.
In order to understand the relationship between aging and working memory, the current study recruited 39 young adult (19-39 years old), 30 middle-aged (40-64 years old) and 30 elderly participants (over 65 years old). All participants had done working memory binding task that emphasize the ability to perform processing, with recoding EEG simultaneously. The analysis method calculation was used Pashler′s K value, d′ and reaction time according to the signal detection theory. EEG analysis used the masking empirical mode decomposition in the Hilbert-Huang Transform. We took the 5th intrinsic mode function as the alpha wave, and calculates the average power of the occipital lobe electrode as the EEG index.
It was observed that the behavioral performance results of the middle-aged group and the young group did not reach the standard of significant difference in Pashler′s K and d′, but the reaction time of the middle-aged group was significantly longer than that of the young group. However, the behavioral performance of the elderly group is significantly worse than that of the young and middle-aged groups in all three indicators. These results had a similar trend with other aging-related studies using different working memory tasks.
In the EEG results, It was observed that prestimulus alpha power is significantly lower in the elderly group than the young group and there is no significant difference between the middle-aged group and the young group. Further analysis, positive correlation between the prestimulus alpha power and Pashler′s K value / d′ was observed, while negative correlation between the prestimulus alpha power and reaction time was observed. In addition, the young group is significantly different from the middle-aged group and the elderly group on the value of alpha suppression in the encoding stage. Positive correlation between the alpha suppression in the encoding stage and Pashler′s K value / d′ was observed.
In summary, this study replicates the results of the decline in working memory with aging in the past, and proposes the relationship between alpha power before stimulation and alpha suppression in encoding stage and working memory aging, and provides objective indicators of working memory performance and aging mechanisms. | en_US |