Academic journal article Attention, Perception and Psychophysics

What Causes Alternations in Dominance during Binocular Rivalry?

Academic journal article Attention, Perception and Psychophysics

What Causes Alternations in Dominance during Binocular Rivalry?

Article excerpt

Several mechanisms have been proposed to account for perceptual alterations during binocular rivalry, including neural adaptation and neural noise. However, the importance of neural adaptation for producing perceptual alterations has been challenged in several articles (Y.-J. Kim, Grabowecky, & Suzuki, 2006; Moreno-Bote, Rinzel, & Rubin, 2007). We devised an "online" adaptation procedure to reexamine the role of adaptation in binocular rivalry. Periods of adaptation inserted into rivalry observation periods parametrically alter the dynamics of rivalry such that increased adaptation duration decreases dominance duration, which cannot be accounted for by neural noise. Analysis of the average dominance durations and their variance (coefficient of variation) provides evidence for an increasingly important role of noise in rivalry alternations as a given dominance period continues in time, consistent with recent computational models.

When an observer is faced with ambiguous or conflicting visual information, perception can fluctuate unpredictably over time between alternative interpretations (C.-Y. Kim & Blake, 2005; Leopold & Logothetis, 1999; Sterzer, Kleinschmidt, & Rees, 2009). Called multistable perception, these rival perceptual states can be experienced when an observer views figures with conflicting figure-ground interpretations or displays in which 3-D surface layout is ambiguous, or when the two eyes receive dissimilar monocular stimuli. These various forms of perceptual multistability exhibit comparable dynamics, with distribution of dominance durations associated with a given perceptual state being unimodal and skewed toward longer durations (Klink, van Ee, & van Wezel, 2008; Leopold & Logothetis, 1999; van Ee, 2005). The similarity of their dynamics suggests that those different forms of multistability may arise from comparable, although not necessarily identical, underlying neural events. What might be the nature of those mechanisms?

To answer this question, it is important to distinguish neural events associated with the representation of a given perceptual state from those that are responsible for switches between alternative perceptual states (Blake & Logothetis, 2002; Sterzer et al., 2009). In the present article, we focus on this latter aspect of multistable perception (i.e., the causes of fluctuations in perception during prolonged viewing of conflicting visual stimuli). According to one view (Pettigrew, 2001), a clocklike neural oscillator triggers perceptual alternations of bistable perception. Consistent with this proposal, alternation rates for different forms of perceptual multistability are correlated across individuals (Carter & Pettigrew, 2003; Sheppard & Pettigrew, 2006). According to another view, whose origin dates back to Helmholtz (1867/1962), perceptual fluctuations arise from a high-level process whereby the brain continuously reevaluates sensory information to update perceptual interpretations (Leopold & Logothetis, 1999). There is suggestive evidence that favors this conceptualization as well (see a recent review by Sterzer et al., 2009). It is not obvious, however, how these two alternative accounts of perceptual alternations would explain a wide range of results showing systematic changes in the dynamics of those alternations dependent on sensory visual properties, such as stimulus contrast, spatial frequency, and luminance (Fahle, 1982; Kang, 2009; Levelt, 1965). Indeed, those kinds of stimulus influences are considerably more robust than are influences attributable to nonsensory factors, such as attention (e.g., Lack, 1978; Meng & Tong, 2004), meaning (e.g., Blake, 1988), and affective connotation (e.g., Alpers & Pauli, 2006). Those kinds of robust visual influences are handled more readily by sensory-based models involving interactions among competing neural representations-models of the sort discussed in the next paragraph. …

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