Dynamics of coding and representation of temporal information in bat auditory cortex and midbrain

前一个项目集中在对回声定位蝙蝠的回声延迟时间敏感的皮层神经元的功能作用上。该项目的主要成果之一是证明，时间神经元调谐是由皮质抑制机制，只有当自然调用回声序列作为刺激时，才起作用，大大锐化。当孤立的和随机呈现的呼叫回声对被用作刺激时，就像以前许多研究中的情况一样，皮层反应更强，但特异性要小得多。这些结果是相当新颖的，并强调使用不仅行为相关的刺激，但刺激序列，而不是孤立的声音事件来研究皮层功能的重要性。在这个延伸项目中，我们的目标是通过（i）研究中脑对自然序列的反应来研究序列特异性加工的机制。这应该有助于确定在皮层中观察到的时间上尖锐的反应的第一个出现点。后者是重要的理解的转换发生沿着上升的听觉通路，使蝙蝠有效地提取信息的回声定位流（ii）在皮层，层特定的贡献序列处理将使用电流源密度分析进行评估，和（iii）我们将分析突触机制，发挥作用的刺激增强抑制GABA能和多巴胺能药物的微离子电渗。这个延伸项目的研究结果应有助于处理和专注于物种相关的信息元素在声学序列中的皮质抑制的作用的一般评估。

The preceding project focussed on the functional role of cortical neurons that are sensitive for echo-delay time in echolocating bats. One of the main results of the project was the demonstration that the temporal neuronal tuning is sharpened considerably by a cortical suppression mechanism that only acts when natural call-echo sequences are used as stimuli. When isolated and randomly presented call-echo pairs are used as stimuli, as it was the case in many previous studies, the cortical responses are stronger but much less specific. These results are quite novel and emphasize the importance of using not only behaviorally relevant stimuli but stimulus sequences rather than isolated sound events to study cortical function. In this elongation project we aim to investigate the mechanisms of sequence-specific processing by (i) studying midbrain responses to natural sequences. This should help to define the first emergence point of the temporally sharp responses observed in the cortex. The latter is important for understanding the transformations that occur along the ascending auditory pathway and that enable bats to effectively extract information from echolocation streams (ii) Within the cortex, layer-specific contributions to sequence processing will be assessed using a current-source density analysis, and (iii) we will analyse synaptic mechanisms that play a role for a stimulus-enhancing suppression by microiontophoresis of GABAergic and glutaminergic pharmaca. The results of this elongation project study should contribute to a general assessment of the role of cortical suppression for processing and focusing on species-relevant information elements in acoustic sequences.