| 研究実績の概要 |
In animal behavior, overcoming disappointments in foraging and courtship, which are often not immediately successful, are critical for survival. Despite these universal and important functions, the neural mechanisms underlying such motivation has not been addressed. This is because, traditionally, an animal behavior model that mimics such motivation has not been linked to a technique for monitoring neural activity in millisecond-order. To address this, we developed a novel rat behavioral task that strongly induces the motivation to overcome unexpected reward omission (disappointment).
Dopamine neurons (DN) in the midbrain ventral tegmental area (VTA) are one of the most important elements of the brain reward system, and have traditionally been thought to play a central role in controlling motivation for passive acceptance of omission of reward ("Reward prediction error" hypothesis). According to this hypothesis, DN activity should decrease when reward is unexpectedly omitted, which in fact has been supported by countless experiments. However, we hypothesized that VTA DN should be also important for the motivation to overcome unexpected omission of reward.
Our study revealed that a subpopulation of DN in the VTA increased activity in response to unexpected omission of reward. By employing calcium imaging technique at single-cell resolution, it was possible to measure the calcium activity of many dopamine neurons simultaneously. Overall, this study clarified the central neural mechanisms responsible for overcoming the omission of reward.
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