Stimulus rivalry and binocular rivalry share a common neural substrate

Abstract

When two incompatible images are shown separately to each eye, a perceptual process known as binocular rivalry occurs by which the two images compete for awareness. The site of competition for binocular rivalry has been a topic of debate, and recent theories are that it may occur either at low levels of the visual system where the inputs from the two eyes are combined or at high levels of the visual system where the two images are processed. One of the major pieces of evidence for a high-level image account of rivalry is a phenomenon known as stimulus rivalry, in which two competing stimuli are swapped between the eyes at 3 Hz. However, there is little available neurophysiological evidence for a neural substrate for this high-level competition. Here, we used frequency tagging of two competing stimuli in binocular rivalry and stimulus rivalry in humans to evaluate whether the steady-state visually evoked potentials (SSVEPs) show similar signatures of neural competition for both conditions. We found that flickering the stimuli generates spectral power at the tagged frequencies in both types of rivalry in the early visual cortex. We then quantified dynamic signatures of competition by tracking amplitude changes in the frequency tags, which showed that both types of rivalry colocalized in occipital regions of the cortex. Thus, contrary to our hypothesis that stimulus rivalry was being mediated by high-level competition between the images, we find that neural competition measured by the SSVEP instead suggests that the sites of competition for stimulus rivalry and binocular rivalry may similarly include the occipital pole and middle temporal gyrus (hMT+/V5) of the visual system, consistent with a low-level, binocular interpretation.

Interocular Grouping in Perceptual Rivalry Localized with fMRI

“…Thus, the additional demands of temporal integration in stimulus rivalry did not greatly interact with the demands of spatial integration. Instead, the results were consistent with earlier conclusions that stimulus rivalry is a weaker form of binocular rivalry with shared neural substrates (Buckthought et al 2015 ; Petruk et al 2018 ). Although we acknowledge the relatively low sample size of this study, we have proceeded cautiously with the aim to offer reproducible conclusions.…”

“…It was thus suggested that stimulus rivalry engages early masking mechanisms that are possibly pre-cortical (Baker and Graf 2009 ; Baker et al 2007 ; Brascamp et al 2013 ). Consistently, Petruk et al ( 2018 ) used SSVEP to show that binocular and stimulus rivalry shared common neural substrates, with an index of competition co-localized in occipital cortex.…”

“…Previous studies have already contrasted the neural substrates of classic binocular and stimulus rivalry in detail (Buckthought et al 2015 ; Petruk et al 2018 ), and we will consider this in the ‘ Discussion ’ section. Our current focus is to evaluate if the addition of interocular grouping affects stimulus rivalry differently than binocular rivalry.…”

“…TMS applied to early cortical visual areas (V1 and surrounding) disrupts normal perceptual alternations during binocular rivalry but not stimulus rivalry (Pearson et al 2007 ). Nevertheless, recent fMRI and MEG studies found a similar pattern of activation for both conditions, but with binocular rivalry producing greater activity (Buckthought et al 2015 ; Petruk et al 2018 ).…”

“…This phenomenon occurs when visual input is ambiguous and compatible with more than one mutually exclusive interpretation (Sterzer et al 2009 ). Paradigms such as binocular rivalry and stimulus rivalry are types of multistable perception that have been widely investigated (e.g., Logothetis et al 1996 ; Lee and Blake 1999 ; Van Boxtel et al 2008 ; Buckthought et al 2015 ; Petruk et al 2018 ). By examining perceptual rivalry, insight can be gained into the neural mechanisms involved in resolving visual ambiguity, fragmentation, and conflict in general (Silver and Logothetis 2004 ; Sterzer et al 2009 ).…”