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Hans-Peter Frey, Marnix Naber, Wolfgang Einhäuser, John Foxe; The role of Gamma oscillations in binding ambiguous visual input into coherent percepts. Journal of Vision 2009;9(8):923. doi: 10.1167/9.8.923.
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© ARVO (1962-2015); The Authors (2016-present)
The question as to how isolated features are bound into coherent object percepts presents a challenge to contemporary neuroscience. Several theoretical and experimental accounts have suggested that oscillatory neural activity in the Gamma range is functionally related to such object integration. Typically, however, such studies cannot fully disentangle stimulus-related (bottom-up) from higher cognitive (top-down) factors. Here we overcome this issue by using an ambiguous figure, whose perceptual interpretation - in the absence of any stimulus changes - alternates between a bound object (moving diamond) and individually moving apertures. Participants indicated these endogenously generated switches, while we recorded high-density EEG. We find a decrease of Gamma power in a narrow band around 40 Hz starting about 500ms before the report of perceptual switches, clearly preceding any motor-related (alpha, mu) activity. This implies a tight temporal coupling of Gamma activity to the process of top-down object binding under ambiguity. This is in line with the purported role of Gamma oscillations in object binding, and additionally suggests a function of Gamma activity in resolving perceptual ambiguity.
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