Research: Eyes right

Spatial attention can boost visual awareness - even without any direct visual input.

Conscious perception is more than just a case of sensory stimulation. Recent research has suggested that spatial attention can influence visual awareness. To investigate this, a team including Sven Bestmann and Jon Driver from the Institute of Neurology, London, used a technique called transcranial magnetic stimulation (TMS) to excite parts of the visual cortex directly.

At an appropriate threshold, TMS causes subjects to 'see' illusions called phosphenes. In the study, subjects were asked to look straight ahead but to concentrate their mental attention on either the left- or right-hand side of their visual field. Whenever subjects focused their attention on one side of their visual field, a lower intensity of TMS was required to produce illusory phosphenes on the corresponding side of the visual cortex.

These findings are further evidence of the importance of 'top-down' influences on the excitation of the visual cortex – i.e. that perception is affected by input from other parts of the brain, even when sensory signals from the eye are 'bypassed'.

External links

• Bestmann S et al. Spatial attention changes excitability of human visualcortex to direct stimulation. Curr Biol 2007;17(2):134–9.