Abstract
Attention allows us to selectively process the vast amount of information with which we are confronted, prioritizing some aspects of information and ignoring others by focusing on a certain location or aspect of the visual scene. Selective attention is guided by two cognitive mechanisms: saliency of the image (bottom up) and endogenous mechanisms (top down). These two mechanisms interact to direct attention and plan eye movements; then, the movement profile is sent to the motor system, which must constantly update the command needed to produce the desired eye movement. A new approach is described here to study how the eye motor control could influence this selection mechanism in clinical behavior: two groups of patients (SCA2 and late onset cerebellar ataxia LOCA) with well-known problems of motor control were studied; patients performed a cognitively demanding task; the results were compared to a stochastic model based on Monte Carlo simulations and a group of healthy subjects. The analytical procedure evaluated some energy functions for understanding the process. The implemented model suggested that patients performed an optimal visual search, reducing intrinsic noise sources. Our findings theorize a strict correlation between the “optimal motor system” and the “optimal stimulus encoders.”
Highlights
The human vision system is a foveocentric structure reflecting the specific anatomical distribution of photoreceptors across the retina, which ensure the best resolution just in a small central region called fovea; outside this region, visual resolution decreases sharply
To assess the differences of exploration strategy among groups, we evaluated distance to nearest region of interest (ROI) (DN) and number of visited regions of interest (Jfix)
ANOVA did not report significant difference on Jfix (P = 0.126, F(2,33) = 2.209) and it was confirmed by posthoc analysis
Summary
The human vision system is a foveocentric structure reflecting the specific anatomical distribution of photoreceptors across the retina, which ensure the best resolution just in a small central region called fovea; outside this region, visual resolution decreases sharply To overcome this perceptive limit, the human brain has developed fast and accurate eye movements (saccades) for pointing the fovea at interesting objects in space [1]. Each saccade landing point represents the locus in space where the fovea gets the most detailed information; outside this point, elements of a scene may be localized but are less accurately distinguished Due to this physiological constraint, the amount of information that can be processed at once by visual system is limited; spatial attention is used to select relevant locations of the visual field for enhanced processing [2] that may occur overtly when associated with an eye movement toward the selected location or covertly without an eye movement. By combining the top down and bottom up information during search, our brain gets a clear view of the conspicuous items
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