编码和提取对项目+背景捆绑机制的影响

The effect of encoding and retrieval on the mechanism of item+context binding

采用事件相关电位（ERP）技术考察了情景记忆编码和提取对语义表征和颜色背景＂捆绑＂神经机制的影响.15名大学生被试参与实验,以汉字为刺激材料,采用学习-测验（背景回忆和背景再认任务）研究范式.数据处理采用事件相关的EEG时频分析、相干分析和独立成分分析（ICA）.结果表明,比较编码中项目＋背景与项目条件,时频分析得到两者之间的差异集中于额区,时程为600~800ms;独立成分分析得到的额区成分说明,2个条件的差异发生在800ms;相干分析得到前额、右顶和左顶-枕区电极的三角形相干结构,2个条件的差异发生在800ms.比较提取过程的项目＋背景与项目条件,时频分析得到两者之间的差异集中于中央顶区和顶枕区,发生在400ms;独立成分分析得到顶枕部脑区成分,2个条件的差异发生在800ms;相干分析得到右半球前部和顶枕部脑区电极的相干成分,2个条件的差异发生在1400ms.研究结果证实,编码和提取对＂捆绑＂的影响不同,这种影响体现在不同脑区参与认知神经活动的程度不同.尤其证实了在提取过程中,顶枕部脑区活动是＂捆绑＂的特异性活动;额-顶枕部相干活动是情景记忆中＂捆绑＂过程普遍存在的大脑活动.

To investigate the neural mechanism of semantic representation and color context binding, EEG （Electroencephalograph） time frequency and coherence analyses were used to reveal local and long-range functional coupling in the encoding and retrieval phases of episodic memory. Fifteen undergraduates participated in the experiment and middle-frequency double-character Chinese words were used as stimuli in two types of study-test tasks （context recall and context recognition tests）. Significant differences between item ＋ context and item in the encoding phase were observed at the electrodes in the frontal region during 600？800 ms by the time frequency analysis. More differences at 800 ms were obtained by ICA analyses： the frontal component as well as the coherent component of triangle phase locking structure between prefrontal, right parietal and left parietal-occipital regions. Furthermore, in the retrieval phase, the differences were obtained on the electrodes at central parietal and parietal-occipital regions at 400 ms by time frequency analysis, on parietal-occipital component at 800 ms by ICA analysis, and on coherence component of anterior right hemisphere and parietal-occipital regions at 1400 ms. In conclusion, we confirmed the different effects of encoding and retrieval processing on ＇binding＇, which was reflected by the different extent of brain regions engaging in the cognitive operations. Especially in retrieval phase, activities of parietal-occipital region were specifically associated with＇binding＇, and coherence between frontal and temporal-parietal regions is a common brain activity in episodic memory.