Hemispheric Asymmetry for Encoding Unrelated Word Pairs? A Functional Near-infrared Spectroscopy Study

目的本研究采用近红外光学成像技术 (fNIRS),探讨双侧前额叶在非相关词对的语义编码过程中的作用.方法 48名被试者分别在深、浅加工2种实验条件下对非相关词对进行编码,光学成像器即时记录在前额叶皮层,波长为760 nm和850 nm的漫射光强变化,以此推测相应脑组织的血容量变化.结果与浅加工相比,在深加工条件下,双侧前额叶中与背外侧前额叶相对应区域的血容量变化都较为明显,尤其是左侧前额叶.本研究结果并不完全支持HERA模型,但与其它相关的脑成像研究结果相似.结论材料的特异性是影响记忆编码中半球一侧化的重要因素,当需要对刺激间的联系进行加工时,右侧前额叶也会参与记忆的编码过程.本研究还提示fNIRS技术可用于记忆等脑高级认知功能的研究.Objective To explore the role of the prefrontal cortex in semantic encoding of unrelated word pairs by using functional near-infrared spectroscopy (fNIRS). Method Forty-eight subjects were presented unrelated pairs of Chinese words under both the nonsemantic and semantic encoding conditions. Under the nonsemantic condition, subjects judged whether the two words had similar orthographic structures; under the semantic condition, they generated a sentence involving the presented word pairs. The changes of regional blood volume associated with the cognitive tasks were measured by using fNIRS equipment which was a continuous optical imager. Result The regions that corresponded to the prefrontal regions showed greater activation under semantic than nonsemantic condition in both left and right hemispheres, although the extent of the activation was larger in the left than right prefrontal regions. This result was consistent with other neuroimaging studies on unrelated word pairs processing, but did not conform to the strict interpretations of the hemispheric encoding/retrieval asymmetry model (HERA). Conclusion This study suggests that material specificity is one of the important factors to influence hemispheric asymmetry in memory encoding. When associations between items are required, right prefrontal regions participate in the encoding processing as well. It also indicates that fNIRS imaging is a viable method of investigating higher level cognitive processing such as memory.Supported by Foundation for the Author of National Excellent Doctoral Dissertation of PRC中文核心期刊要目总览(PKU)中国科学引文数据库(CSCD)05318-3231