Schacter D L, Wagner A D
Department of Psychology, Harvard University, Cambridge, Massachusetts 02138, USA.
Hippocampus. 1999;9(1):7-24. doi: 10.1002/(SICI)1098-1063(1999)9:1<7::AID-HIPO2>3.0.CO;2-K.
Early neuroimaging studies often failed to obtain evidence of medial temporal lobe (MTL) activation during episodic encoding or retrieval, but a growing number of studies using functional magnetic resonance imaging (fMRI) and positron emission tomography (PET) have provided such evidence. We review data from fMRI studies that converge on the conclusion that posterior MTL is associated with episodic encoding; too few fMRI studies of retrieval have reported MTL activations to allow firm conclusions about their exact locations. We then turn to a recent meta-analysis of PET studies (Lepage et al., Hippocampus 1998;8:313-322) that appears to contradict the fMRI encoding data. Based on their analysis of the rostrocaudal distribution of activations reported during episodic encoding or retrieval, Lepage et al. (1998) concluded that anterior MTL is strongly associated with episodic encoding, whereas posterior MTL is strongly associated with episodic retrieval. After considering the evidence reviewed by Lepage et al. (1998) along with additional studies, we conclude that PET studies of encoding reveal both anterior and posterior MTL activations. These observations indicate that the contradiction between fMRI and PET studies of encoding was more apparent than real. However, PET studies have reported anterior MTL encoding activations more frequently than have fMRI studies. We consider possible sources of these differences.
早期的神经影像学研究常常未能获得内侧颞叶（MTL）在情景编码或检索过程中激活的证据，但越来越多使用功能磁共振成像（fMRI）和正电子发射断层扫描（PET）的研究提供了此类证据。我们回顾了fMRI研究的数据，这些数据得出了一致的结论，即MTL后部与情景编码相关；关于检索的fMRI研究报告MTL激活的太少，无法就其确切位置得出确凿结论。然后，我们转向最近一项对PET研究的荟萃分析（勒佩奇等人，《海马体》1998年；8：313 - 322），该分析似乎与fMRI编码数据相矛盾。基于他们对情景编码或检索过程中报告的激活的前后分布分析，勒佩奇等人（1998年）得出结论，MTL前部与情景编码密切相关，而MTL后部与情景检索密切相关。在考虑了勒佩奇等人（1998年）回顾的证据以及其他研究后，我们得出结论，PET编码研究揭示了MTL前部和后部的激活。这些观察结果表明，fMRI和PET编码研究之间的矛盾比实际情况更明显。然而，PET研究报告MTL前部编码激活的频率比fMRI研究更高。我们考虑了这些差异可能的来源。
