Paying attention affects the picture
Visually localising objects in space requires integration of information about head position, eye position and the physical location of the stimuli on the retina. Recent studies have challenged previous models, suggesting that the neural maps of visual space do not depend only on the retino-cortical projections, but can also be modified by contextual factors such as depth information or attention processes during the very earliest processing stages. EU-funded scientists on the project 'Attention warps early sensory maps' (AWESOME) applied advanced behavioural and neuroimaging techniques to systematically study the neural substrates of visual space perception. They presented the subject with stimuli as brief flashes during shifts in attention or gaze direction, and measured physiological changes such as pupil reflexes as well as the impact on the retinotopic maps. Functional magnetic resonance imaging (fMRI) helped determine if the representation of the flashes on the retinotopic maps corresponds to the real or perceived position of the stimuli. Researchers developed a novel algorithm to decode fMRI responses in early visual areas into a map of represented space. Results suggest that the perceived maps of space are extremely flexible and inputs are remapped depending on the behavioural context. Additional behavioural experiments revealed a strong parallel between spatial distortions and attention shifts and indicate that the effects of attention can be traced down to the very first stage of visual processing – the eye, since even the rudimentary pupillary reflex to light is affected by the subject’s behavioural context. The diameter of the pupil is automatically regulated by the amount of ambient light, a reflex action that is involuntary. However, AWESOME researchers found that the regulation of pupil size is enhanced or suppressed when the subject's attention is focused upon or away from the light source. More generally, pupil size depends not just on light but on its perceptual interpretation; a key example is that the pupil constricted when the subject was shown photographs of the sun. Groundbreaking results have been published in prestigious peer-reviewed journals and presented at eight international conferences, generating widespread interest. AWESOME research results have important clinical implications. If sensory processing is so deeply affected by attention and behaviour, it follows that deficits of the latter will also impact basic sensory abilities. Realizing this could be the basis for development of new perspectives on treatment of conditions such as autism spectrum and attention deficit hyperactivity disorder.
Keywords
Attention, visual processing, sensory maps, pupillary light reflex, functional magnetic resonance imaging