Predictably manipulating photoreceptor light responses to reveal their role in downstream visual responses

Computation in neural circuits relies on the judicious use of nonlinear circuit components. In many cases, multiple nonlinear components work collectively to control circuit outputs. Separating the contributions of these different components is difficult, and this limits our understanding of the mechanistic basis of many important computations. Here, we introduce a tool that permits the design of light stimuli that predictably alter rod and cone phototransduction currents - including stimuli that compensate for nonlinear properties such as light adaptation. This tool, based on well-established models for the rod and cone phototransduction cascade, permits the separation of nonlinearities in phototransduction from those in downstream circuits. This will allow, for example, direct tests of how adaptation in rod and cone phototransduction affects downstream visual signals and perception.

神经环路中的计算依赖于对非线性环路组件的审慎运用。在诸多场景中，多个非线性组件会协同调控环路的输出信号。厘清这些不同组件的功能贡献颇具难度，这也限制了我们对诸多关键计算过程的机制基础的认知。本研究引入一款工具，可设计出可预见性地调控视杆细胞（rod）与视锥细胞（cone）光转导电流的光刺激方案——其中包含可补偿光适应（light adaptation）等非线性特性的刺激范式。该工具基于已被广泛验证的视杆细胞与视锥细胞光转导级联反应模型，能够将光转导过程中的非线性特性与下游环路中的非线性特性分离开来。借此，研究人员可直接验证视杆细胞与视锥细胞光转导过程中的适应机制如何影响下游视觉信号与感知认知。