Ludwig-Maximilians-Universität München
print

Language Selection

Breadcrumb Navigation


Content

“He holds him with his glittering eye”

Visual attention predicts what the eye will see

Munich, 12/27/2010

The fovea is the area of the retina with the highest visual acuity. Objects in the visual field must be targeted on the center of this area to be perceived with high spatial resolution. This targeting is made possible by rapid movements of the eye, called saccades, which are controlled by oculomotor muscles. A research team including LMU psychologists Donatas Jonikaitis and Professor Heiner Deubel, together with Dr. Martin Rolfs and Professor Patrick Cavanagh of the Université Paris Descartes, has now investigated why our perception of a given scene remains stable despite the fact that the eyeball frequently moves. It turns out that visual attention is redirected, before each saccade, to the point at which the object will appear after the saccadic movement is executed. This anticipatory mechanism enables us to keep targets of interest stably “in our sights”. (Nature Neuroscience online 26. December 2010)

With every saccadic movement, i.e. three to four times a second, the position of the image on the retina shifts dramatically, drifting at high speed relative to the background. This, of course, is not what we experience, so obviously the human brain is capable of combining the sensory impressions received before and after every saccade in such a way as to achieve the spatial and temporal continuity we perceive. It is known that neurons in several brain regions in the cerebral cortex, including the so-called lateral intraparietal area (LIP), are activated to stimuli prior to each saccade, although these signals only become relevant after the next saccade has been executed.

The LMU researchers and their colleagues in Paris set out to test the idea that the apparently “premature” activation of these neurons is associated with an anticipatory shift of visual attention to the position to which the image of the relevant object will be relocated by the following saccade. Since visual attention is not necessarily coupled to a sharply focused gaze, one’s eyes can remain fixated on a particular area, while one’s visual attention has already been reoriented to some point in the periphery of the visual field.

Indeed, the team was able to demonstrate that, before the onset of a saccade, a measurable improvement in visual acuity occurs in the sector of the visual field in which the object will appear after the eyeball moves. In addition, further tests revealed that this anticipatory shift of attention is a precondition for rapid execution of the subsequent saccade. “We are the first to describe this particular type of anticipatory shift in visual attention”, says Deubel. “Perhaps this economical but effective mechanism is what enables us to ‘keep an eye on things’, despite the fact that our eyes repeatedly execute rapid movements”.

The findings alter our views regarding the function of the anticipatory activity of cortical neurons, and have implications that go beyond their significance for basic research. Among other possibilities, the new results may enhance our understanding of the visual problems that many stroke victims experience, or they could find application in the field of robotics, perhaps leading to improvements in coordination between sensory information and movement. Psychologist Donatas Jonikaitis – a graduate of the international MSc program in Neurocognitive Psychology, which is financially supported at LMU by the Elitenetzwerk Bayern (ENB) – made a considerable contribution to the newly published work. He will also supervise the follow-up project – and one of the goals of that study will be to clarify whether similar predictive shifts play a role in the execution of tasks involving a combination of eye and hand movements.

 

Contact:
Prof. Heiner Deubel
Department of Psychology
Ludwig-Maximilians-Universität (LMU) in Munich
Phone: +49 (0) 89 / 2180 5282
E-mail: heiner.deubel@psy.lmu.de

Donatas Jonikaitis
Department of Psychology
Ludwig-Maximilians-Universität (LMU) in Munich
Phone: +49 (0) 89 / 2180 6229
E-mail: djonikaitis@googlemail.com

Responsible for content: Communications & Media Relations