Decoding the Direction of Bistable Illusory Motion from Source-Reconstructed MEG Signals

Motion perception involves both bottom-up sensory processing and top-down perceptual interpretation. Using MEG frequency tagging and source-space multivariate pattern analysis, we decoded the perceived direction of both real and bistable apparent motion from cortical activity in 11 human participants (6 male, 5 female). Real motion direction was decoded with near-ceiling accuracy across frequencies in both whole-brain and visual-cortex analyses, whereas apparent-motion direction was decoded just above chance from visual cortex (56.0%, p=0.011, Cohen's d=0.94) when combining the 5 and 7.5 Hz harmonics. Activation patterns showed a larger relative hMT+ contribution for apparent than real motion, and cross-classification did not generalize direction information between conditions. These results identify a measurable cortical signature of subjective motion direction but also show that it is relatively diffuse and only weakly bound to retinotopic cortex.Significance Statement How does the brain represent what we perceive consciously when the physical stimulus is ambiguous? Using a bistable apparent-motion display (in which the image is fixed but its perceived direction spontaneously switches) together with MEG frequency tagging and source-space decoding, we show that the perceived direction of illusory motion can be read out from activity in visual cortex. Decoding of real motion was near-perfect and dominated by primary visual cortex (V1), whereas for illusory motion decoding was only slightly above chance and the human motion complex hMT+ contributed equally with V1. These findings reveal a relative shift away from retinotopic visual areas when perception is constructed rather than stimulus-driven.