本文结合我们的研究,总结了国内外近十几年来利用功能性核磁共振(functional magnetic resonance image,fMRI)技术对记忆编码和提取功能在大脑结构上表达的研究成果。在不同刺激材料、不同记忆类型和不同年龄条件下,记忆编码和提取激活的脑区是不完全相同的,并具有大脑半球偏侧化差异。如对语义知识的编码和提取主要依赖于左侧大脑半球的前额叶和颞叶,而对图像、空间信息的编码和提取则主要依赖于右侧大脑半球的前额叶和颞叶。表明这些功能的神经网络基础不相同。在记忆编码和提取时激活的脑区有重叠也有区别,记忆编码主要定位于前额叶、颞叶、顶叶、海马前部、基底节和丘脑,记忆提取主要定位于前额叶、颞叶、海马后部、基底节、丘脑、旁嗅皮质和嗅皮质。编码时激活的皮层结构强度和范围较提取时多,而提取时激活的皮层下结构较编码时多。在海马结构中,编码时主要激活海马的前部,而提取时主要激活海马的后部。可以设想记忆编码和提取过程是由大脑内皮层-皮层下结构(主要是基底节和丘脑)-皮层形成的神经环路共同完成的,不是单由大脑皮层完成的;皮层下结构在二者的神经环路中都起到"中继站"的作用。
Abstract: Memory encoding and memory retrieval are two important processes of the memory. The main results of studies on the neural basis of the memory encoding and memory retrieval by functional magnetic resonance image (fMRI) technique were summarized in this review. The neural basis of memory encoding and retrieval phases varies with different materials, memory types, and age stages. It means that the neural networks of these memory activities are separate. The functional locations of the activated brain areas during memory encoding and during memory retrieval phases are overlapped with distinction. The activated brain areas of memory encoding mainly locate in the prefrontal lobe, the temporal lobe, the parietal lobe, the anterior hippocampus, the thalamus, and the basal ganglia (including the striatum and the marginal division of the striatum). The activated brain areas of memory retrieval mainly locate in the prefrontal lobe, the temporal lobe, the entorhinal cortex, the perirhinal cortex, the posterior hippocampus, the thalamus, and the basal ganglia. The anterior hippocampus is mainly activated during the encoding phase, whereas posterior hippocampus is mainly activated during the retrieval phase. The intensity of the activated cerebral cortex regions during the encoding phase is stronger than that during the retrieval phase, whereas the opposite activated pattern is found in the subcortical structures, mainly the basal ganglia and thalamus, during the two phases. It seems that the stimulation might activate certain cerebral cortex areas during the memory encoding phase, then the information is transported to the subcortical structures and comes back to the cerebral cortex to complete the memory retrieval phase. The encoding and retrieval phases of the memory are supposed to be accomplished by a neural circuit among the cerebral cortex, basal ganglia, thalamus and cerebral cortex, rather than the cerebral cortex only.