Understanding how the brain decodes sensory information to give rise to behaviour remains an important problem in systems neuroscience. Across various sensory modalities (e.g. auditory, visual), the time-varying contrast of natural stimuli has been shown to carry behaviourally relevant information. However, it is unclear how such information is actually decoded by the brain to evoke perception and behaviour. Here we investigated how midbrain electrosensory neurons respond to weak contrasts in the electrosensory system of the weakly electric fish Apteronotus leptorhynchus. We found that these neurons displayed lower detection thresholds than their afferent hindbrain electrosensory neurons. Further analysis revealed that the lower detection thresholds of midbrain neurons were not due to increased sensitivity to the stimulus. Rather, these were due to the fact that midbrain neurons displayed lower variability in their firing activities in the absence of stimulation, which is due to lower firing rates. Our results suggest that midbrain neurons play an active role towards enabling the detection of weak stimulus contrasts, which in turn leads to perception and behavioral responses.

理解大脑如何解码感官信息以引起行为仍然是系统神经科学中的重要问题。在各种感觉方式（例如听觉，视觉）中，自然刺激的时变对比已显示出行为相关的信息。但是，目前尚不清楚大脑如何真正解码此类信息以唤起感知和行为。在这里，我们研究了中脑电感应神经元如何响应弱电鱼拟南芥的电感应系统中的弱对比。。我们发现这些神经元显示出比其传入后脑电感应神经元更低的检测阈值。进一步的分析表明，中脑神经元的较低检测阈值并不是由于对刺激的敏感性增加。相反，这是由于以下事实：在没有刺激的情况下，中脑神经元的放电活动具有较低的变异性，这是由于较低的放电速率所致。我们的结果表明，中脑神经元在激活弱刺激对比的检测中起着积极作用，进而导致感知和行为反应。