• binocular rivalry
• endogenous attention
• interocular grouping
• pupillometry

Binocular rivalry is a peculiar form of visual bistability that occurs when the two eyes are presented with markedly different stimuli: although retinal stimulation remains constant, the observer typically perceives one stimulus at a time, and perception alternates between the two stimuli at irregular intervals ( J.W.Brascamp et al.,2015) Binocular Rivalry was systematically studied for the first time by Charles Wheatstone in 19th century and from then on many researchers focused on this phenomenon as a tool for studying the neural correlates of visual consciousness (Blake et al., 2014).
My project is aimed to study the perceptual dynamics, the physiological biomarkers and the influence of endogenous attention regarding two different forms of rivalry: classic binocular rivalry and interocular grouping rivalry. The latter occurs when different parts of an image presented to each eye bound into a coherent whole (Kovacs et al.,1996).
Our analyses focus on the behavioral parameters that express the perceptual strength of each percept, as well as on a physiological biomarker, the variation in pupil diameter (recorded with EyeLink1000). The rationale for this is that oscillations of pupil diameter are known to be closely related to perceptual rivalry (Naber et al., 2011). For this purpose, administrating dichoptic stimuli, two main conditions were tested for both binocular rivalry and interocular grouping rivalry rivalry: no-cue (in which subjects simply reported their visual perception) and endogenous attention (in which participants were instructed to focus on either one of the two stimuli).
In line with previous studies, which reported pupil dilation as following perceived stimuli rather than physical ones in binocular rivalry, we detected different pupillary dilation levels depending on the perceived stimulus luminance in both forms of bistability.
Importantly, we found the perceptual dynamics, though not pupil oscillations, to be affected by endogenous attention in both kinds of stimuli.
Our pupillometry data and the possibility to directly compare binocular and inter-ocular grouping rivalry give an important contribution in the understanding of the neural basis of bi stable perception.