Purchase this article with an account.
Yuranny Cabral-Calderin, Carsten Schmidt-Samoa, Melanie Wilke; Role of gamma oscillations in visual awareness.. Journal of Vision 2013;13(9):1030. doi: 10.1167/13.9.1030.
Download citation file:
© ARVO (1962-2015); The Authors (2016-present)
Synchronized alpha/beta (8–30 Hz) and gamma (>30 Hz)-band oscillations in the visual cortex are suggested to be important for visual awareness (Wilke et al,2006; Fries et al,1997; Uhlhaas et al, 2009). In the present study, we used transcranial alternating current stimulation (tACS) in combination with functional MRI to test the causal role of oscillatory activity in visual perception. tACS is thought to entrain endogenous neuronal oscillations in a given frequency range (Stagg & Nitsche, 2011). Twenty-two healthy subjects were reporting their percepts of a "Structure-from-Motion" (SfM) stimulus while receiving tACS. In the SfM paradigm, an ambiguous sphere is perceived to rotate either to the left or to the right, and the direction of rotation switches spontaneously over time. The behavioral results showed that tACS in the higher gamma range (60 Hz) increased the number of perceptual reversals in comparison with the sham condition. In contrast, tACS in the alpha (10 Hz) and beta (16 Hz) frequency ranges did not affect perceptual states. In order to evaluate the changes in neural activity as a function of tACS-stimulation, we next combined tACS with fMRI while subjects were reporting their percepts of the SfM stimulus. In agreement with previous SfM studies (Sterzer et al, 2009), the comparison between spontaneous reversals of perceived motion direction and physical replay revealed increased BOLD activity in visual cortex, superior parietal lobe and insular cortex during spontaneous reversals. Most importantly, comparing sham with 60 Hz before the perceptual reversals showed an increase in BOLD signals in visual cortex as well as cingulate and insular cortex. Taken together, our results provide evidence for a causal role of gamma oscillations in perceptual reversals and point to a critical involvement of cingulate and insular cortex in resolving perceptual ambiguity.
Meeting abstract presented at VSS 2013
This PDF is available to Subscribers Only