NEURAL BASES OF SEMANTIC MEMORY

语义记忆指的是关于物体、事实、概念和单词及其含义的知识。对语义记忆的神经基础的兴趣来自于对语义记忆显著受损的患者的观察，尽管他们的认知功能完好无损。这种损伤最常在退行性疾病中观察到：语义记忆损伤是阿尔茨海默病最早和最突出的特征之一，语义知识的丧失是与皮克病相关的一种称为“语义痴呆”综合征的决定性特征。单纯疱疹脑炎、脑后动脉梗死、缺氧缺血性损伤和肿瘤切除患者也会出现语义记忆障碍。在研究正常认知的现代神经成像技术的发展的帮助下，这些观察导致了对语义记忆的神经基础的猜测。这两种方法（病变研究和成像研究）已经确定了两个可能专门用于语义记忆的区域：左颞叶皮层和左前额叶皮层。基于文献分析和一些初步发现，我们假设前额叶皮层和颞叶皮层在语义记忆中起着截然不同的作用；前额叶皮层对于竞争性信息的选择是必要的，而不是语义检索本身。该项目主要有四个目标：(1)证明前额叶皮层和颞叶皮层在语义记忆中的作用是分离的；(2)从认知和神经两方面更精确地描述颞叶皮层语义重复效应的本质；(3)进一步发展前额叶皮层支持竞争性信息选择的假设，并将这一假设与竞争性选择区分开来；(4)利用影像与损伤相结合的方法，为语义记忆的神经基础提供证据。

Semantic memory refers to knowledge about objects, facts, concepts, and words and their meanings. Interest in the neural bases of semantic memory comes from observations of patients with striking impairments in semantic memory despite otherwise intact cognitive functioning. Such impairments are observed most commonly in degenerative diseases: semantic memory impairments are one of the earliest and most prominent features of Alzheimer's disease, and loss of semantic knowledge is the defining feature of a syndrome known as "semantic dementia", associated with Pick's disease. Impairments of semantic memory have also been observed in patients with herpes simplex encephalitis, posterior cerebral artery infarctions, hypoxic-ischemic injury, and tumor resection. These observations have led to speculation about the neural bases of semantic memory, aided by the development of modern neuroimaging techniques for studying normal cognition. These two methods (lesion studies and imaging studies) have identified two regions that may be specialized for semantic memory: left temporal cortex and left prefrontal cortex. Based on an analysis of the literature and some preliminary findings, we hypothesize that prefrontal and temporal cortex play quite distinct roles in semantic memory; and that prefrontal cortex is necessary for the selection of competing information, and not for semantic retrieval per se. The proposed project has four major goals: (1) to demonstrate a dissociation between the roles of prefrontal cortex and temporal cortex in semantic memory; (2) to describe in more precise terms, both cognitively and neurally, the nature of semantic repetition effects in temporal cortex; (3) to develop further the hypothesis that prefrontal cortex subserves the selection of competing information and to distinguish this hypothesis from competing alternatives; (4) to provide converging evidence as to the neural bases of semantic memory with complementary imaging and lesion methodologies.