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Alyse Brown, Molly Corner, David Crewther, Sheila Crewther; Human flicker fusion frequencies correlate negatively with cortical VEP magnocellular nonlinearities. Journal of Vision 2017;17(10):735. doi: 10.1167/17.10.735.
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© ARVO (1962-2015); The Authors (2016-present)
The temporal speed with which the brain processes visual information has important implications for our ability to attend, process and respond to our environment in real time. However, the mechanisms behind the temporal thresholds in visual perception are poorly understood. Perceptual processing speed is based, in part, on the recovery speeds of the Magnocellular (M) and Parvocellular (P) visual pathways. Here we compared psychophysically determined flicker frequency thresholds with M and P contributions to the nonlinearities generated in electrophysiological recordings over primary visual cortex. Smaller nonlinearities are proposed to be associated with greater neural efficiency in the visual system and the predominant M nonlinearity was predicted to negatively correlate with achromatic flicker frequency threshold. LED driven achromatic sinusoidal flicker fusion frequencies for high (75%) and low (5%) temporal contrasts were compared, using 76 typically developing young adults, with the M and P nonlinearities of the multifocal Visual Evoked Potential (mfVEP), recorded from occipital scalp (Oz). Flicker task performances showed an effect of contrast with the 5% modulation showing a lower mean threshold than the 95% modulation. As predicted, flicker thresholds for high (r= -.319, n=69, p < .003) and low (r= -.216, n=68, p < .036) contrast negatively correlated with the amplitude of the main M nonlinearity (K2.1 [N60-P90]) component, indicating that perceptual speed of processing is linked to more efficient cortical processing. This is the first study to directly correlate a non-linear component of the VEP to a psychophysically measured visual threshold - flicker fusion frequency. Furthermore, this finding should help consolidate the link between primate and human studies by showing that a physiological measure of Magnocellular function based on primate contrast response functions links a putatively Magnocellular response limit to high frequency flicker.
Meeting abstract presented at VSS 2017
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