Visual Awareness in Binocular Rivalry Modulates Induced Pupil Fluctuations

Area of Science:

• Neuroscience
• Visual Perception
• Psychophysics

Background:

• Pupil size naturally tracks luminance oscillations in visual stimuli.
• Pupil oscillations can be modulated by covert attention, a phenomenon known as pupil frequency tagging.
• Binocular rivalry involves the competition between two different visual stimuli presented to each eye, leading to alternating perception.

Purpose of the Study:

• To investigate if pupil frequency tagging can be extended to infer perceptual awareness in binocular rivalry.
• To determine if pupil response phase correlates with which complex stimulus (face or house) is perceived.
• To assess the feasibility of decoding perceptual dominance from pupil oscillations.

Main Methods:

• Two distinct stimuli (face and house) were presented to each eye, with luminance modulated at 1.7 Hz.
• Stimuli luminance modulation was applied in counter-phase (180°), 90° phase shift, or in-phase (0° control).
• Observers' perceptual dominance was recorded, and pupil response phase was analyzed in relation to stimulus phase and awareness.

Main Results:

• The phase of the pupil response significantly correlated with perceptual dominance for 180° and 90° phase-shifted stimuli.
• The perceptually dominant stimulus could be decoded from the pupil response phase above chance levels.
• No significant phase dependence or decoding was observed in the 0° in-phase control condition.

Conclusions:

• Visual awareness dynamically modulates induced pupil oscillations.
• Pupil frequency tagging provides a viable method for inferring perceptual dominance during binocular rivalry with complex stimuli.
• This technique offers a novel, objective measure to study the neural correlates of visual awareness.