During associative conditioning, animals learn which sensory cues are predictive for positive or negative conditions. Because sensory cues are encoded by distributed neurons, one has to monitor plasticity across many synapses to capture how learned information is encoded. We analyzed synaptic boutons of Kenyon cells of the Drosophila mushroom body γ lobe, a brain structure that mediates olfactory learning. A fluorescent Ca²⁺ sensor was expressed in single Kenyon cells so that axonal boutons could be assigned to distinct cells and Ca²⁺ could be measured across many animals. Learning induced directed synaptic plasticity in specific compartments along the axons. Moreover, we show that odor-evoked Ca²⁺ dynamics across boutons decorrelate as a result of associative learning. Information theory indicates that learning renders the stimulus representation more distinct compared with naive stimuli. These data reveal that synaptic boutons rather than cells act as individually modifiable units, and coherence among them is a memory-encoding parameter.

在联想条件下，动物会了解哪些感觉线索可预测阳性或阴性情况。由于感觉线索是由分布式神经元编码的，因此必须监视许多突触的可塑性，以捕获学习信息的编码方式。我们分析了果蝇蘑菇体γ瓣的Kenyon细胞的突触钮扣，这是介导嗅觉学习的大脑结构。在单个Kenyon细胞中表达了荧光Ca ²⁺传感器，因此可以将轴突纽扣分配给不同的细胞，并且可以在许多动物中测量Ca ²⁺。学习在沿轴突的特定区域诱导定向的突触可塑性。此外，我们证明了气味诱发的Ca ²⁺联想学习的结果是，各个按键之间的动力学去相关。信息理论表明，与幼稚的刺激相比，学习使刺激的表现更加鲜明。这些数据表明，突触钮扣而不是细胞是可单独修改的单元，并且它们之间的连贯性是记忆编码参数。