A normative theory of forgetting: lessons from the fruit fly.
A normative theory of forgetting: lessons from the fruit fly.
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DOI：
10.1371/journal.pcbi.1003640
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发表时间：
2014-06
影响因子：
4.3
通讯作者：
Senn W
中科院分区：
文献类型：
--
作者：
Brea J;Urbanczik R;Senn W
最近的实验表明，果蝇（Drosophila melanogaster）有一种专门的遗忘机制：阻断G蛋白Rac导致遗忘速度减慢，激活Rac导致遗忘速度加快。这种主动的遗忘形式缺乏令人满意的功能解释。我们研究了适应随机环境的代理的最优决策，其中刺激可以在指示奖励或惩罚之间切换。像果蝇一样，最佳代理人的遗忘率与环境变化的时间尺度有关。此外，为了减少错过未来奖励的可能性，最佳代理人可能会用即时疼痛的风险来换取信息增益，从而在厌恶条件反射后更快地忘记。一个简单的神经元网络再现了这些特征。我们的理论表明，遗忘在果蝇中表现为一种在变化的环境中的最佳适应行为。这与遗忘是适应性的观点一致，而不是记忆系统限制的结果。在科学和社会中，遗忘的主要观点是，它是实现更好的记忆表现的一种麻烦。然而，最近在果蝇身上进行的实验表明，遗忘率在生物化学上与环境相适应，这让人怀疑较慢的遗忘本身是否是一个理想的特征。在这里，我们表明，事实上，在一个随机变化的环境中的最佳行为需要一个遗忘率，是适应的变化的时间常数。果蝇的行为与经典的最优性准则相容，即选择最大化未来回报的行动。未来奖励最大化的一个后果是，为了不错过奖励机会，应该迅速忘记导致胆小行为的负面经验。在经济学中，这被称为“机会成本最小化”，而果蝇似乎很关心这个问题：惩罚比奖励更容易被遗忘。遗忘作为一种最优特性，可以进一步解释具有不同会话间隔的多个训练会话的不同记忆表现，正如在从苍蝇到人类的各种物种中观察到的那样。这些方面建议将遗忘视为适应性行为的一个维度，以适应环境，以最大限度地提高主观利益。
Recent experiments revealed that the fruit fly Drosophila melanogaster has a dedicated mechanism for forgetting: blocking the G-protein Rac leads to slower and activating Rac to faster forgetting. This active form of forgetting lacks a satisfactory functional explanation. We investigated optimal decision making for an agent adapting to a stochastic environment where a stimulus may switch between being indicative of reward or punishment. Like Drosophila, an optimal agent shows forgetting with a rate that is linked to the time scale of changes in the environment. Moreover, to reduce the odds of missing future reward, an optimal agent may trade the risk of immediate pain for information gain and thus forget faster after aversive conditioning. A simple neuronal network reproduces these features. Our theory shows that forgetting in Drosophila appears as an optimal adaptive behavior in a changing environment. This is in line with the view that forgetting is adaptive rather than a consequence of limitations of the memory system. The dominant perception of forgetting in science and society is that it is a nuisance in achieving better memory performance. However, recent experiments in the fruit fly show that the forgetting rate is biochemically adapted to the environment, raising doubts that slower forgetting per se is a desirable feature. Here we show that, in fact, optimal behavior in a stochastically changing environment requires a forgetting rate that is adapted to the time constant of the changes. The fruit fly behavior is compatible with the classical optimality criterion of choosing actions that maximize future rewards. A consequence of future reward maximization is that negative experiences that lead to timid behavior should be quickly forgotten in order to not miss rewarding opportunities. In economics this is called “minimization of opportunity costs”, and the fruit fly seems to care about it: punishment is forgotten faster than reward. Forgetting as a trait of optimality can further explain the different memory performances for multiple training sessions with varying inter-session intervals, as observed in a wide range of species from flies to humans. These aspects suggest to view forgetting as a dimension of adaptive behavior that is tuned to the environment to maximize subjective benefits.
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影响因子：
2
作者：
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通讯作者：
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