Second-order motion perception in peripheral vision: limits of early filtering

Area of Science:

• Visual neuroscience
• Perceptual psychology

Background:

• Second-order motion stimuli, like contrast-modulated gratings, are composed of a carrier and sidebands.
• Early visual processing involves linear spatial filtering that can impact the perception of these stimuli.

Purpose of the Study:

• To investigate how early linear spatial filtering affects second-order motion perception.
• To determine the conditions under which motion direction is perceived correctly or reversed.

Main Methods:

• Used contrast-modulated sine-wave gratings presented centrally and peripherally.
• Employed a two-alternative forced-choice staircase paradigm to assess motion direction identification.

Main Results:

• Perceived motion direction reversed in the periphery when envelope frequency was near carrier frequency.
• Higher envelope spatial frequencies caused reversed motion perception both centrally and peripherally.
• Specific carrier-to-envelope spatial frequency ratios were needed for correct motion perception in foveal and peripheral vision.

Conclusions:

• Early linear spatial filtering in the visual system can lead to reversed perception of second-order motion.
• The findings support a linear model of motion detection with spatial filtering.
• Carrier undersampling has minimal impact on peripheral second-order motion perception if the carrier is detectable.