2013年9月9日月曜日

Prolonged dopamine signalling in striatum signals proximity and value of distant rewards

Mark W. Howe, Patrick L. Tierney, Stefan G. Sandberg, Paul E. M. Phillips & Ann M. Graybiel
Nature (2013) doi:10.1038/nature12475
Received 25 January 2013 Accepted 17 July 2013 Published online 04 August 2013

ラットの迷路課題。
ドーパミンはゴール(報酬が貰える地点)までの「距離(所要時間ではなく)」をコードしている(TD強化学習における「価値」とは異なる変数なのかな?)。
→ モチベーションのコントロールに重要な役割を果たすと考えられる。

Predictions about future rewarding events have a powerful influence on behaviour. The phasic spike activity of dopamine-containing neurons, and corresponding dopamine transients in the striatum, are thought to underlie these predictions, encoding positive and negative reward prediction errors1, 2, 3, 4, 5. However, many behaviours are directed towards distant goals, for which transient signals may fail to provide sustained drive. Here we report an extended mode of reward-predictive dopamine signalling in the striatum that emerged as rats moved towards distant goals. These dopamine signals, which were detected with fast-scan cyclic voltammetry (FSCV), gradually increased or—in rare instances—decreased as the animals navigated mazes to reach remote rewards, rather than having phasic or steady tonic profiles. These dopamine increases (ramps) scaled flexibly with both the distance and size of the rewards. During learning, these dopamine signals showed spatial preferences for goals in different locations and readily changed in magnitude to reflect changing values of the distant rewards. Such prolonged dopamine signalling could provide sustained motivational drive, a control mechanism that may be important for normal behaviour and that can be impaired in a range of neurologic and neuropsychiatric disorders.

0 件のコメント:

コメントを投稿