Matlab code & Customized plastic holder - CFF test

Recent studies highlight the importance of the temporal domain in visual processing. Critical Flicker Frequency (CFF), the frequency at which a flickering light is perceived as continuous, is a widely used measure for evaluating visual temporal processing. Another important issue to investigate is the cortical interactions arising between the flicker stimuli of both eyes.
This data presents a robust and reliable dichoptic tool for evaluating the CFF threshold in both eyes. This system is based on an analog output device used to independently drive two LEDs through a custom-written MATLAB code (using a laptop PC) for eliciting sinusoidal flickering stimuli and for psychophysically measuring the perceived CFF threshold. The luminance and phases of each LED are individually controlled, enabling the investigation of the effect of phase and luminance differences on binocular summation in subjects with different ocular pathologies. Experiments were designed to evaluate the CFF threshold through a psychophysical test, based on a discrimination task with a stimulus duration of 1 sec, based on a temporal alternative forced-choice paradigm. The target stimulus temporal features were modulated using the staircase method. Subjects were requested to discriminate between a target stimulus (a flickering light at various frequencies) and a flickering light at a frequency of 120Hz, which is significantly higher than the CFF in humans; therefore, it is perceived as constant.
One of the main advantages of the introduced dichoptic presentation system is that it enables the visual temporal performance to be measured under both monocular and binocular conditions where phenomena such as temporal binocular summation (BS) can be evaluated. Moreover, the system offers great flexibility by introducing a stimulus phase shift, which enables studying how stimulus timing affects the temporal function at millisecond scale resolution.

Here we provide all necessary computer code that will enable an easy and quick adaptation of the method by scientists interested in studying the temporal resolution of the visual system in general, and in studying inter-ocular differences or interactions in particular.

近期研究凸显了时域在视觉信息处理中的重要性。临界闪烁频率（Critical Flicker Frequency, CFF），即闪烁光源被感知为连续光时的临界频率，是评估视觉时域处理能力的常用指标。另一个值得探究的重要议题是双眼闪烁刺激之间所引发的皮层交互作用。
本数据集提供了一种稳健可靠的双眼分视（dichoptic）工具，用于评估双眼的临界闪烁频率阈值。该系统基于一款模拟输出设备，借助笔记本电脑运行自定义编写的MATLAB代码，可独立驱动两颗发光二极管（LED），以生成正弦波闪烁刺激，并通过心理物理学方法测量被试感知到的临界闪烁频率阈值。每颗LED的亮度与相位均可独立调控，借此可探究相位与亮度差异对不同眼部疾病患者双眼总和效应的影响。实验设计采用基于时域迫选范式的辨别任务，刺激时长为1秒，以此通过心理物理学测试评估临界闪烁频率阈值。目标刺激的时域特征通过阶梯法进行调控。要求被试在两种闪烁刺激间进行辨别：一种为不同频率的闪烁目标刺激，另一种为频率120Hz的闪烁光——该频率显著高于人类的临界闪烁频率，因此会被感知为恒定光源。
本次提出的双眼分视呈现系统的核心优势之一，是可在单眼与双眼两种条件下测量视觉时域表现，从而可评估时域双眼总和（binocular summation, BS）等相关现象。此外，该系统通过引入刺激相位偏移具备极强的灵活性，可在毫秒级分辨率下探究刺激时序对时域功能的影响。
本文提供了全部所需的计算机代码，以供致力于研究视觉系统时域分辨率（尤其关注双眼间差异或交互作用）的科研人员能够便捷快速地适配该实验方法。