Visual discomfort, neural inefficiency and the cortical haemodynamic response

We show that visual perception of an image becomes uncomfortable when the image evokes a large haemodynamic response. The aversion of gaze that results therefore has the potential to reduce the use of energy by the brain. We consider four features of images from nature, and show that unless the image has each feature, it is rated as relatively uncomfortable to view. The cortical haemodynamic response evoked is then larger than when the image is more natural and more comfortable. There are large differences between observers as regards discomfort from images. The cortical haemodynamic response is larger in observers who experience discomfort. The relationship between visual discomfort and the amplitude of the cortical haemodynamic response therefore applies both across stimuli and across observers. We propose that the unnatural visual images encountered in urban life result in inefficient neural processing and are detrimental to health.