State Key Laboratory of Brain and Cognitive Science, Institute of Biophysics, Chinese Academy of Sciences, Beijing, China.
Eur J Neurosci. 2009 Jul;30(2):279-88. doi: 10.1111/j.1460-9568.2009.06821.x. Epub 2009 Jul 15.
The brain mechanisms by which animals deal with multiple experiences to predict outcomes are not yet fully understood. We explored the choice strategies that flies use to assess degrees of disadvantage, as well as how flies weigh past and recent experiences to guide decisions. Drosophila were exposed to two conditioning events in a T-maze: an odor paired with an electric shock followed by a second odor paired with an electric shock of a different intensity. Subsequently, flies were forced to choose between the two odors. We found that flies chose to avoid the more 'dangerous' odor by a linear subtraction mechanism that was based on two coexisting memories. We also found that flies weighed experiences of the same danger level (60 V electric shocks) according to the times when the experiences had occurred. More recent experiences had a greater impact and past experiences gradually became 'overlooked' during decisions as the time delay between the two events lengthened. However, the past memory was not so much disrupted as it was overshadowed by recent memories during decisions. Finally, when a past experience was more disadvantageous, wild-type flies were able to coordinate both the temporal factor and the degree of disadvantage into their decisions. By contrast, amnesiac mutant flies made choices completely according to the temporal factor, ignoring the degree of disadvantage. Taken together, wild-type flies are able to store multiple olfactory memories and can coherently evaluate learned experiences to guide their decisions according to the degree of disadvantage and/or the temporal factor.
动物通过多种经验处理来预测结果的大脑机制尚未完全理解。我们探讨了苍蝇用来评估劣势程度的选择策略，以及苍蝇如何权衡过去和最近的经验来指导决策。苍蝇在 T 型迷宫中经历了两次条件作用事件：一种气味与电击配对，然后是另一种气味与不同强度的电击配对。随后，苍蝇被迫在两种气味之间做出选择。我们发现，苍蝇通过基于两种共存记忆的线性减法机制来选择避免更“危险”的气味。我们还发现，苍蝇根据经历发生的时间来权衡相同危险水平（60V 电击）的经验。最近的经历影响更大，随着两个事件之间的时间延迟延长，过去的经历在决策过程中逐渐被“忽略”。然而，过去的记忆并没有被完全打乱，而是在决策过程中被最近的记忆所掩盖。最后，当过去的经历更不利时，野生型苍蝇能够将时间因素和劣势程度协调到它们的决策中。相比之下，健忘突变体苍蝇完全根据时间因素做出选择，忽略了劣势程度。总之，野生型苍蝇能够储存多种嗅觉记忆，并能够根据劣势程度和/或时间因素来协调评估学习经验以指导决策。
