Collinear features impair visual detection by rats

TL;DR

This study demonstrates that collinear visual features impair rats' ability to detect targets, revealing a pattern-sensitive effect on visual processing despite the absence of orientation columns in their visual cortex.

Contribution

It provides the first evidence that feature arrangement affects visual detection in rats and introduces a novel automated method for high-throughput behavioral testing.

Findings

Rats are less likely to detect targets with collinear flankers.

The impairment persists even with luminance sign reversal of flankers.

Feature arrangement influences visual processing in rats.

Abstract

We measure rats' ability to detect an oriented visual target grating located between two flanking stimuli ("flankers"). Flankers varied in contrast, orientation, angular position, and sign. Rats are impaired at detecting visual targets with collinear flankers, compared to configurations where flankers differ from the target in orientation or angular position. In particular, rats are more likely to miss the target when flankers are collinear. The same impairment is found even when the flanker luminance was sign-reversed relative to the target. These findings suggest that contour alignment alters visual processing in rats, despite their lack of orientation columns in visual cortex. This is the first report that the arrangement of visual features relative to each other affects visual behavior in rats. To provide a conceptual framework for our findings, we relate our stimuli to a contrast normalization model of early visual processing. We suggest a pattern-sensitive generalization of the model which could account for a collinear deficit. These experiments were performed using a novel method for automated high-throughput training and testing of visual behavior in rodents.