A team of researchers including our own Antti Revonsuo have just published a paper in NeuroImage entitled ‘Early processing in primary visual cortex is necessary for conscious and unconscious vision while late processing is necessary only for conscious vision in neurologically healthy humans.’
Briefly, the study found that activity in the primary visual cortex at an early (60 ms) stage was involved in both conscious and unconscious processing of visual stimuli, while activity at a later (90 ms) stage was only involved in aspects of conscious processing.