Asymmetric Processing of Visual Motion for Simultaneous Object and Background Responses
Asymmetric Processing of Visual Motion for Simultaneous Object and Background Responses
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DOI：
10.1016/j.cub.2014.10.042
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发表时间：
2014-12-01
期刊：
影响因子：
9.2
通讯作者：
Straw, Andrew D.
中科院分区：
文献类型：
--
作者：
Fenk, Lisa M.;Poehlmann, Andreas;Straw, Andrew D.
果蝇的视觉对象固定和图形背景辨别是鲁棒的行为，需要视觉系统进行复杂的计算，但神经基础仍然未知。最近在行走的果蝇中进行的实验揭示了由电路介导的物体固定行为，该电路独立于宽场运动反应所需的运动敏感 T4-T5 细胞 [1]。在闭环条件下的系留飞行实验中，我们发现了一种反馈增益的类似结果，而完整的 T4-T5 细胞对于在较高反馈增益和图形-地面辨别任务中稳健的对象固定是必需的。我们基于 T4-T5 细胞下游的神经元实现了动态模型（可在 http://strawlab.org/asym-motion/ 获得），一个是简单的现象学模型，另一个是生理学上更现实的模型，发现两者都预测条纹固定和图形-背景辨别的关键特征，并且与经典公式一致 [2]。这两个模型的基础是模型神经元响应中的运动不对称，因此从前到后的运动比从后到前的运动引起更强的响应。当双边一对此类模型神经元（基于 T4-T5 [5] 下游的众所周知的水平系统细胞 [3, 4]）与转动行为耦合时，不对称性会导致在存在噪声的情况下物体固定和图形-背景辨别。此外，这些模型还预测在移动背景前的注视，之前认为这种行为需要额外的途径[1]。因此，模型根据神经元预测物体反应的几个方面，这些神经元也被认为在背景稳定中发挥着关键作用[6-12]。
Visual object fixation and figure-ground discrimination in Drosophila are robust behaviors requiring sophisticated computation by the visual system, yet the neural substrates remain unknown. Recent experiments in walking flies revealed object fixation behavior mediated by circuitry independent from the motion-sensitive T4-T5 cells required for wide-field motion responses [1]. In tethered flight experiments under closed-loop conditions, we found similar results for one feedback gain, whereas intact T4-T5 cells were necessary for robust object fixation at a higher feedback gain and in figure-ground discrimination tasks. We implemented dynamical models (available at http://strawlab.org/asymmetric-motion/) based on neurons downstream of T4-T5 cells-one a simple phenomenological model and another, physiologically more realistic model-and found that both predict key features of stripe fixation and figure-ground discrimination and are consistent with a classical formulation [2]. Fundamental to both models is motion asymmetry in the responses of model neurons, whereby front-to-back motion elicits stronger responses than back-to-front motion. When a bilateral pair of such model neurons, based on well-understood horizontal system cells [3, 4], downstream of T4-T5 [5], is coupled to turning behavior, asymmetry leads to object fixation and figure-ground discrimination in the presence of noise. Furthermore, the models also predict fixation in front of a moving background, a behavior previously suggested to require an additional pathway [1]. Thus, the models predict several aspects of object responses on the basis of neurons that are also thought to serve a key role in background stabilization [6-12].