Fotowat Haleh, Gabbiani Fabrizio
Department of Neuroscience, Baylor College of Medicine, Houston, Texas 77030, USA.
J Neurosci. 2007 Sep 12;27(37):10047-59. doi: 10.1523/JNEUROSCI.1515-07.2007.
The firing patterns of visual neurons tracking approaching objects need to be translated into appropriate motor activation sequences to generate escape behaviors. Locusts possess an identified neuron highly sensitive to approaching objects (looming stimuli), thought to play an important role in collision avoidance through its motor projections. To study how the activity of this neuron relates to escape behaviors, we monitored jumps evoked by looming stimuli in freely behaving animals. By comparing electrophysiological and high-speed video recordings, we found that the initial preparatory phase of jumps occurs on average during the rising phase of the firing rate of the looming-sensitive neuron. The coactivation period of leg flexors and extensors, which is used to store the energy required for the jump, coincides with the timing of the peak firing rate of the neuron. The final preparatory phase occurs after the peak and takeoff happens when the firing rate of the looming-sensitive neuron has decayed to <10% of its peak. Both the initial and the final preparatory phases and takeoff are triggered when the approaching object crosses successive threshold angular sizes on the animal's retina. Our results therefore suggest that distinct phases of the firing patterns of individual sensory neurons may actively contribute to distinct phases of complex, multistage motor behaviors.
追踪接近物体的视觉神经元的放电模式需要转化为适当的运动激活序列，以产生逃避行为。蝗虫拥有一种对接近物体（逼近刺激）高度敏感的已鉴定神经元，据认为该神经元通过其运动投射在避免碰撞中发挥重要作用。为了研究该神经元的活动如何与逃避行为相关，我们监测了自由行为动物中由逼近刺激诱发的跳跃。通过比较电生理和高速视频记录，我们发现跳跃的初始准备阶段平均发生在逼近敏感神经元放电率的上升阶段。用于储存跳跃所需能量的腿部屈肌和伸肌的共同激活期与神经元放电率峰值的时间一致。最终准备阶段发生在峰值之后，当逼近敏感神经元的放电率衰减至其峰值的<10%时发生起跳。当接近物体在动物视网膜上越过连续的阈值角大小时，初始和最终准备阶段以及起跳都会被触发。因此，我们的结果表明，单个感觉神经元放电模式的不同阶段可能积极地促成复杂的多阶段运动行为的不同阶段。
