During binocular rivalry, where each eye sees a different image and perception alternates between them, the brain activity corresponding to the consciously perceived image shows increased synchronization. Red vertical and blue horizontal gratings were presented to each eye, each flickering at a distinct frequency. Magnetoencephalography recorded stronger steady-state magnetic fields at the frequency of the perceived grating over occipital, temporal, and frontal cortices. Coherence analysis revealed increased interhemispheric and intrahemispheric synchronization at the stimulus frequency when that stimulus was perceived. The results demonstrate a direct correlation between conscious perception and synchronous activity of large populations of neocortical neurons.
During binocular rivalry, where each eye sees a different image but only one is consciously perceived at a time, neuromagnetic responses in the brain show activity at frequencies corresponding to both stimuli, even for the unseen one. However, when a stimulus is not consciously perceived, the power of its neural response is reduced by 50-85% across many brain regions, including areas outside the visual cortex. This modulation is widespread but not global, indicating that conscious perception correlates with the strength of synchronized neural activity in large neuronal populations.