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| Notger Mueller |
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Dpt. of Neurology, J. W. Goethe-University, Frankfurt/M, Germany
e-mail: n.mueller@em.uni-frankfurt.de |
Poster Presentation: |
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| A PHYSIOLOGICAL CORRELATE OF THE ZOOM LENS OF VISUAL ATTENTION. |
| NG Mueller , OA Bartelt, TH Donner, A Villringer, SA Brandt | |
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J. W. Goethe-University, Frankfurt/M, Germany and Humboldt University Berlin |
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| Attending a certain region in space enhances activity in visual areas retinotopically mapped to this region and stimuli presented in this region are preferentially processed. The zoom lens model of visual attention proposes that the attended region can be adjusted in size and predicts a tradeoff between its size and processing efficiency due to limited processing capacities. By means of event-related fMRI, we analyzed neural activity in multiple visual areas as a function of the size of an attended visual field region, which was defined by a spatial cue stimulus. After cueing, a target object, defined by a specific feature conjunction, had to be identified among objects within the cued region. Neural activity preceding the objects in multiple retinotopic visual areas correlated with the size of the attended region as did subjects’ performance. While the quantity of activated retinotopic subregions increased with the size of the attended region, the level of neural activity in a given subregion decreased. These findings are consistent with the physiological predictions of the zoom lens model. Size-related modulations of neural activity were pronounced in early visual areas. We relate this finding to the necessity of feature conjunction for target identification which required precise spatial selection based on small receptive fields (RFs). Under narrowly focused attention, selected neurons with RFs coding the attended location received an enhancing top-down bias. When objects were presented, this bias may have gated processing of the features of the object at the attended location, thus enabling feature integration and object identification. |
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