2015年3月13日金曜日

Functionally Dissociable Influences on Learning Rate in a Dynamic Environment

Joseph T. McGuire, Matthew R. Nassar, Joshua I. Gold, Joseph W. Kable
Neuron, Volume 84, Issue 4, 19 November 2014, Pages 870–881

最適な学習には学習率を適切に調節することが重要である。
その調節には、「驚きに度合い」、「不確実性」、「報酬」の三つの要素が効いている。
また、上記の要素は、視覚野、前頭前野/頭頂葉、腹側線条体でそれぞれ処理されている。

Maintaining accurate beliefs in a changing environment requires dynamically adapting the rate at which one learns from new experiences. Beliefs should be stable in the face of noisy data but malleable in periods of change or uncertainty. Here we used computational modeling, psychophysics, and fMRI to show that adaptive learning is not a unitary phenomenon in the brain. Rather, it can be decomposed into three computationally and neuroanatomically distinct factors that were evident in human subjects performing a spatial-prediction task: (1) surprise-driven belief updating, related to BOLD activity in visual cortex; (2) uncertainty-driven belief updating, related to anterior prefrontal and parietal activity; and (3) reward-driven belief updating, a context-inappropriate behavioral tendency related to activity in ventral striatum. These distinct factors converged in a core system governing adaptive learning. This system, which included dorsomedial frontal cortex, responded to all three factors and predicted belief updating both across trials and across individuals.

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