2013年1月30日水曜日

Interaction Between Orbital Prefrontal and Rhinal Cortex Is Required for Normal Estimates of Expected Value


Andrew M. Clark, Sebastien Bouret, Adrienne M. Young, Elisabeth A. Murray, and Barry J. Richmond
The Journal of Neuroscience, 30 January 2013, 33(5): 1833-1845; doi: 10.1523/​JNEUROSCI.3605-12.2013

側頭葉内側部とOFCの相互作用を阻害すると報酬量の推定ができなくなる。「視覚刺激に基づく推定」だけでなく「コンテクストに基づく推定(ブロック毎に報酬量が変化)」も。両部位の相互作用は色々な状況での価値推定に広く関与している。 http://www.jneurosci.org/content/33/5/1833

Predicting and valuing potential rewards requires integrating sensory, associative, and contextual information with subjective reward preferences. Previous work has identified regions in the prefrontal cortex and medial temporal lobe believed to be important for each of these functions. For example, activity in the orbital prefrontal cortex (PFo) encodes the specific sensory properties of and preferences for rewards, while activity in the rhinal cortex (Rh) encodes stimulus-stimulus and stimulus–reward associations. Lesions of either structure impair the ability to use visual cues or the history of previous reinforcement to value expected rewards. These areas are linked via reciprocal connections, suggesting it might be their interaction that is critical for estimating expected value. To test this hypothesis, we interrupted direct, intra-hemispheric PFo-Rh interaction in monkeys by performing crossed unilateral ablations of these regions (functional disconnection). We asked whether this circuit is crucial primarily for cue–reward association or for estimating expected value per se, by testing these monkeys, as well as intact controls, on tasks in which expected value was either visually cued or had to be inferred from block-wise changes in reward size in uncued trials. Functional disconnection significantly affected performance in both tasks. Specifically, monkeys with functional disconnection showed less of a difference in error rates and reaction times across reward sizes, in some cases behaving as if they expected rewards to be of equal magnitude. These results support a model whereby information about rewards signaled in PFo is combined with associative and contextual information signaled within Rh to estimate expected value.

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