Elsevier

NeuroImage

Volume 221, 1 November 2020, 117173
NeuroImage

Manipulating the structure of natural scenes using wavelets to study the functional architecture of perceptual hierarchies in the brain

https://doi.org/10.1016/j.neuroimage.2020.117173Get rights and content
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Abstract

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.

Keywords

Visual cortex
image processing
3T
fMRI
human
natural images
film stimuli
toolbox
dynamic natural scenes

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