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Tomas Knapen, Joel Pearson, Jan Brascamp, Raymond van Ee, Randolph Blake; The role of frontal areas in alternations during perceptual bistability. Journal of Vision 2008;8(6):254. doi: 10.1167/8.6.254.
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© ARVO (1962-2015); The Authors (2016-present)
When viewing ambiguous visual stimulation, observers may experience perceptual competition wherein mutually exclusive perceptual interpretations compete for dominance over time. When contrasted with ‘replay’ conditions, in which unambiguous stimuli evoking these perceptual interpretations are physically interchanged over time, ambiguous alternations lead to activation of a large network of occipital, parietal and frontal cortical regions. The brain, in other words, responds uniquely when invariant physical stimulation leads to perceptual fluctuations.
Using functional magnetic resonance imaging (fMRI), we investigated the roles of separate elements of this network of cortical regions using a bistable apparent motion stimulus, in which a sinusoidally counterphased spiral figure induces one of two distinct rotational motion percepts over time. Additionally, during the course of an extended observation period, transitions between motion percepts are occassioned by periods of non-directional flicker perception that cannot be realistically simulated in replay presentations; the incidence of these periods of indistinct motion increase with prolonged viewing, suggesting the involvement of neural adaptation.
During whole-brain fMRI scans performed at 3T, observers pressed buttons to indicate periods of clear motion perception and periods of flicker perception. Contrasting these two types of events, we could distinguish activity in various brain regions associated with perceptual transitions from one motion percept to the other, from motion to flicker and from flicker to motion. These contrasts revealed that frontal areas respond to the onset of flicker, whereas parietal regions respond preferentially to the onset of motion percepts.
These results shed new light on the different roles played by cortical areas previously implicated in perceptual rivalry. Specifically, we propose that the activity in frontal cortex is associated with periods of perceptual uncertainty that can occur during transitions between rival states.
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