School of Psychology, The University of Queensland, Brisbane QLD 4072, Australia; Queensland Brain Institute, The University of Queensland, Brisbane QLD 4072, Australia.
School of Psychology, University of Wollongong, Wollongong NSW 2522, Australia.
Neuroimage. 2020 Nov 1;221:117173. doi: 10.1016/j.neuroimage.2020.117173. Epub 2020 Jul 17.
Functional neuroimaging experiments that employ naturalistic stimuli (natural scenes, films, spoken narratives) provide insights into cognitive function "in the wild". Natural stimuli typically possess crowded, spectrally dense, dynamic, and multimodal properties within a rich multiscale structure. However, when using natural stimuli, various challenges exist for creating parametric manipulations with tight experimental control. Here, we revisit the typical spectral composition and statistical dependences of natural scenes, which distinguish them from abstract stimuli. We then demonstrate how to selectively degrade subtle statistical dependences within specific spatial scales using the wavelet transform. Such manipulations leave basic features of the stimuli, such as luminance and contrast, intact. Using functional neuroimaging of human participants viewing degraded natural images, we demonstrate that cortical responses at different levels of the visual hierarchy are differentially sensitive to subtle statistical dependences in natural images. This demonstration supports the notion that perceptual systems in the brain are optimally tuned to the complex statistical properties of the natural world. The code to undertake these stimulus manipulations, and their natural extension to dynamic natural scenes (films), is freely available.
采用自然刺激（自然场景、电影、口头叙述）的功能神经影像学实验为认知功能的“自然状态”提供了深入了解。自然刺激通常在丰富的多尺度结构中具有拥挤、光谱密集、动态和多模态的特性。然而，当使用自然刺激时，创建具有严格实验控制的参数操作会存在各种挑战。在这里，我们重新审视了自然场景的典型光谱组成和统计依赖性，这些特征使它们与抽象刺激区分开来。然后，我们展示了如何使用小波变换选择性地降低特定空间尺度内微妙的统计依赖性。这种操作使刺激的基本特征（如亮度和对比度）保持完整。我们使用观看自然图像退化的人类参与者的功能神经影像学，证明了视觉层次结构不同水平的皮质反应对自然图像中微妙的统计依赖性具有不同的敏感性。这一演示支持了这样一种观点，即大脑中的感知系统是针对自然世界的复杂统计特性进行最佳调整的。进行这些刺激操作的代码，以及将其自然扩展到动态自然场景（电影）的代码是免费提供的。
