The Neural Mechanisms Of Implicit Memory And The Separation Of Implicit Long Memory Erps

The short- and long-term dissociation of explicit memory has been thoroughly investigated while such dissociation in implicit memory rarely received attention. There been different views on the relationship between working memory and consciousness. Most current studies on implicit working memory are behavioral. With sophisticated experimental design and reaction time index, they proved the existence of implicit component in working memory. However, these behavior studies lack for neurophysiological support and did not explore the different brain activities behind the reaction times. In this study, using the event-related ERP technology with high time resolution, in experiment 1 the existence and electrophysiological mechanism of implicit working memory was investigated in a modified visual pattern-reversal task. In experiment 2, the dynamic dissociation between short- and long term implicit memory was explored with a lexical decision task.The main results from the research are as follows:(1) The differences between "Pattern" and "Broken pattern" in experiment 1 and the dissociation between short- and long-term repetition priming in experiment 2 show that implicit working memory does exist.(2) The neural mechanisms of implicit spatial working memory share similarities with explicit spatial working memory, and it also has its unique features. Both of them show closely related P2 and late negative waveform. However, while the mid-term and late negative waveforms were largest in the centro-parietal site in implicit working memory, the largest waveforms were in the occipital site in the explicit working memory.(3)The priming effect of the words can be divided into two components in the time course. The short-term component followed by a fast and steady decay and the long-term component maintained for approximately 15 lags (26.3s). For the non-words, the short-term component only appeared after the immediate repetition, then rapidly dropped to the maintenance in the long-term component.(4)Without considering the intervening items, words and non-words showed similar repetition priming ERP patterns, while they only have differences between 200-600ms in the prefrontal cortex.(5)The short term priming activated earlier and larger ERPs than long term priming, while they have no significant difference in prefrontal area.In this study, our results improved related theory and provided neurophysiological evidences for the existence of implicit working memory. At the same time, the results of this study also provided the basis for us to explain for some phenomenon, such as learning and memory and other phenomenon that occurred in the daily life.