Research: Brain registers moving bodies without being consciously aware of them

24 March 2006

The brain can visually register moving bodies without being consciously aware of them.

One of the oddities of the human visual system is its ability to register objects even in the absence of conscious awareness. A visual stimulus, for example, can be 'masked' – so a subject has no conscious awareness of having seen it – if a second strong stimulus is given straight after. The brain has registered the first stimulus, however – it reacts more strongly if it sees it again.

Dr K Moutoussis and Professor Semir Zeki, from University College London, have shown that the same can be true of moving stimuli. Our peripheral vision is good at spotting movement, but a particular moving stimulus can be 'crowded out' by other stimuli around it, so it is not consciously registered.

However, functional imaging reveals that a key area of the visual brain (known as V5), thought to be crucial to the conscious perception of motion, is still activated even when stimuli have been crowded out.

Thus V5 activation is not always associated with conscious awareness of motion. Perhaps, the authors suggest, conscious awareness in key areas such as V5 is dependent on activity reaching a threshold, or successfully 'competing' with other active areas to register in conscious experience.

External links

• Moutoussis K, Zeki S. Seeing invisible motion: a human FMRI study. Curr Biol 2006;16(6):574–9.