The link between fMRI-BOLD activation and perceptual awareness is “stream-invariant” in the human visual system

Abstract

A central topic of controversy in the search for cortical mechanisms underlying perceptual awareness concerns the fundamental specialization of the visual system into a dorsal "vision-for-action/Where" stream and a ventral "vision-for-perception/What" stream. Specifically, it has been debated whether suppression of visual perception leads to differential reduction in brain activity in the 2 streams--with the dorsal stream remaining largely unaffected and the ventral stream showing a significant reduction in activity. Here, we examined this issue using the recently introduced method of continuous flash suppression (CFS), which offers a particularly sensitive measure of the link between perception and brain activity. Subjects had to detect, during CFS, images of manipulable man-made objects (tools). Our results show that despite their substantial difference in connectivity and neuroanatomical specialization, both ventral and dorsal stream areas revealed a similarly tight link to perceptual awareness, that is, strong functional magnetic resonance imaging-blood oxygenation level-dependent activity for visible tools but a significant reduction of activity in the invisible condition. Importantly, this result was found when the masks were kept identical in the visible and invisible conditions. Our data lend support to the notion that neuronal activity and perceptual awareness are tightly linked across human high-order visual cortex.