Abstract
Behavioral studies in humans and rats demonstrate that visual detection of a target stimulus is sensitive to surrounding spatial patterns. In both species, the detection of an oriented visual target is affected when the surrounding region contains flanking stimuli that are collinear to the target. In many studies, collinear flankers have been shown to improve performance in humans, both absolutely (compared to performance with no flankers) and relative to non-collinear flankers. More recently, collinear flankers have been shown to impair performance in rats both absolutely and relative to non-collinear flankers. However, these observations spanned different experimental paradigms. Past studies in humans have shown that the magnitude and even sign of flanker effects can depend critically on the details of stimulus and task design. Therefore either task differences or species could explain the opposite findings. Here we provide a direct comparison of behavioral data between species and show that these differences persist – collinear flankers improve performance in humans, and impair performance in rats – in spite of controls that match stimuli, experimental paradigm, and learning procedure. There is evidence that the contrasts of the target and the flankers could affect whether surround processing is suppressive or facilitatory. In a second experiment, we explored a range of contrast conditions in the rat, to determine if contrast could explain the lack of collinear facilitation. Using different pairs of target and flanker contrast, the rat’s collinear impairment was confirmed to be robust across a range of contrast conditions. We conclude that processing of collinear features is indeed different between rats and humans. We speculate that the observed difference between rat and human is caused by the combined impact of differences in the statistics in natural retinal images, the representational capacity of neurons in visual cortex, and attention.
Highlights
Specialized interaction of nearby collinear features is thought to play an important role in contour integration and figure/ground segregation of scenes
The many possible stimulus patterns were organized into three groups for analysis: trials without any flanking stimuli (“no flanker”), trials with two collinear flankers (“collinear”), and trials with two flankers present, neither of which was collinear to the target (“non-collinear”)
Flankers with collinear spatial patterns had the strongest effect on performance
Summary
Specialized interaction of nearby collinear features is thought to play an important role in contour integration and figure/ground segregation of scenes. Collinear features enjoy prominent statistical correlations across spatial regions and feature types. It has been suggested (Barlow, 1961; Olshausen and Field, 1996; Simoncelli and Olshausen, 2001; Coen-Cagli et al, 2012) that neurons learn to represent the world by exploiting the joint statistics between their inputs. Cortical computation may latch on to events induced by collinear stimuli, and appropriately enhance or suppress them. We argue that a good way to begin understanding the cortical code is to examine the neural and behavioral responses to stimuli with features that are correlated in the natural world, but are made independent in the course of the study. We directly compare the behavioral responses of humans and rats detecting a visual target surrounded by collinear flankers
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
