Department of Bioengineering, Imperial College London London, UK.
Front Syst Neurosci. 2010 Nov 23;4:153. doi: 10.3389/fnsys.2010.00153. eCollection 2010.
Flying generates predictably different patterns of optic flow compared with other locomotor states. A sensorimotor system tuned to rapid responses and a high bandwidth of optic flow would help the animal to avoid wasting energy through imprecise motor action. However, neural processing that covers a higher input bandwidth itself comes at higher energetic costs which would be a poor investment when the animal was not flying. How does the blowfly adjust the dynamic range of its optic flow-processing neurons to the locomotor state? Octopamine (OA) is a biogenic amine central to the initiation and maintenance of flight in insects. We used an OA agonist chlordimeform (CDM) to simulate the widespread OA release during flight and recorded the effects on the temporal frequency coding of the H2 cell. This cell is a visual interneuron known to be involved in flight stabilization reflexes. The application of CDM resulted in (i) an increase in the cell's spontaneous activity, expanding the inhibitory signaling range (ii) an initial response gain to moving gratings (20-60 ms post-stimulus) that depended on the temporal frequency of the grating and (iii) a reduction in the rate and magnitude of motion adaptation that was also temporal frequency-dependent. To our knowledge, this is the first demonstration that the application of a neuromodulator can induce velocity-dependent alterations in the gain of a wide-field optic flow-processing neuron. The observed changes in the cell's response properties resulted in a 33% increase of the cell's information rate when encoding random changes in temporal frequency of the stimulus. The increased signaling range and more rapid, longer lasting responses employed more spikes to encode each bit, and so consumed a greater amount of energy. It appears that for the fly investing more energy in sensory processing during flight is more efficient than wasting energy on under-performing motor control.
飞行产生的光流模式与其他运动状态可预测地不同。一个对快速反应和高带宽光流敏感的感觉运动系统将有助于动物避免因不准确的运动行为而浪费能量。然而，覆盖更高输入带宽的神经处理本身需要更高的能量成本，当动物不飞行时，这将是一个糟糕的投资。食蚜蝇如何将其光流处理神经元的动态范围调整到运动状态？章鱼胺（OA）是一种生物胺，对昆虫的飞行启动和维持至关重要。我们使用 OA 激动剂氯二甲酮（CDM）模拟飞行期间广泛的 OA 释放，并记录对 H2 细胞的时间频率编码的影响。该细胞是一种已知参与飞行稳定反射的视觉中间神经元。CDM 的应用导致（i）细胞自发活动增加，扩大抑制信号范围；（ii）对运动光栅的初始响应增益（刺激后 20-60ms）取决于光栅的时间频率；（iii）运动适应的速率和幅度降低，这也与时间频率有关。据我们所知，这是第一个证明应用神经调质可以诱导宽视野光流处理神经元的增益与速度相关变化的演示。细胞反应特性的观察到的变化导致当编码刺激的时间频率随机变化时，细胞的信息率增加 33%。信号范围的增加和更快、更持久的反应使用更多的尖峰来编码每个位，因此消耗了更多的能量。看来，对于飞行中的苍蝇来说，在感官处理上投入更多的能量比在表现不佳的运动控制上浪费能量更有效率。
