2013年10月16日水曜日

Dissociable Neural Mechanisms for Goal-Directed Versus Incidental Memory Reactivation

Brice A. Kuhl, Marcia K. Johnson, and Marvin M. Chun
J. Neurosci. 2013;33 16099-16109

ヒトfMRI。
「実験課題の遂行に必要(Goal-Directed)な情報を記憶から呼び出す」のと「課題遂行に必要ない偶発的(Incidental)な情報を呼び出す」のはどう違うのか?
腹内側頭葉(ventral/medial temporal lobe: VMTL)は両者に関連する。つまり、記憶の呼び出し一般を司る。
一方、前頭頭頂皮質は前者のみに関連。つまり、何らかの目的に応じて記憶を呼び出すことに関与している。

Remembering a past event involves reactivation of distributed patterns of neural activity that represent the features of that event—a process that depends on associative mechanisms supported by medial temporal lobe structures. Although efficient use of memory requires prioritizing those features of a memory that are relevant to current behavioral goals (target features) over features that may be goal-irrelevant (incidental features), there remains ambiguity concerning how this is achieved. We tested the hypothesis that although medial temporal lobe structures may support reactivation of both target and incidental event features, frontoparietal cortex preferentially reactivates those features that match current goals. Here, human participants were cued to remember either the category (face/scene) to which a picture belonged (category trials) or the location (left/right) in which a picture appeared (location trials). Multivoxel pattern analysis of fMRI data were used to measure reactivation of category information as a function of its behavioral relevance (target vs incidental reactivation). In ventral/medial temporal lobe (VMTL) structures, incidental reactivation was as robust as target reactivation. In contrast, frontoparietal cortex exhibited stronger target than incidental reactivation; that is, goal-modulated reactivation. Reactivation was also associated with later memory. Frontoparietal biases toward target reactivation predicted subsequent memory for target features, whereas incidental reactivation in VMTL predicted subsequent memory for nontested features. These findings reveal a striking dissociation between goal-modulated reactivation in frontoparietal cortex and incidental reactivation in VMTL.

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