Saliency maps and top-down guidance in the human brain
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1
Max Planck Institute for Brain Research, Germany
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2
Department of Neurology, Otto-von-Guericke University, Germany
Whether an object captures our attention depends on its bottom-up salience, i.e., how different it is compared to its neighbors, and top-down control, i.e., our current inner goals. At which neuronal stage they interact to guide behavior is still unknown. Here, we tested whether top-down and bottom-up attention are already coordinated at the level of early visual areas (V1-hV4), and which cerebral networks are responsible for top-down control. Using functional magnetic resonance imaging (fMRI), we assessed neural responses in retinotopic representations of target and distractor stimuli during a visual search task while manipulating bottom-up and top-down factors. We find evidence for a hierarchy of saliency maps in human early visual cortex (V1 to hV4) and identify where bottom-up saliency interacts with top-down control: V1 represents pure bottom-up signals, V2 is only responsive to top-down modulations, and in hV4 bottom-up saliency and top-down control converge. Two distinct cerebral networks exert top-down control: distractor suppression engages temporo-parietal junction, medial frontal gyrus and intraparietal sulcus, while target enhancement involves frontal eye field, lateral and ventral occipital cortex. Crucially, activation in frontal regions was higher when reaction times were slowest and activation in early visual areas was lowest, seemingly compensating a reduction in early saliency processing. Our results provide evidence of hierarchically organized saliency maps in human visual cortex and emphasize that top-down guidance plays a role even when bottom-up distinctiveness is high. The integrated maps in visual cortex provide precise topographic information about target and distracter locations and, therefore, allow for successful visual search.
Keywords:
Attention,
Saliency maps
Conference:
XI International Conference on Cognitive Neuroscience (ICON XI), Palma, Mallorca, Spain, 25 Sep - 29 Sep, 2011.
Presentation Type:
Poster Presentation
Topic:
Poster Sessions: Neurophysiology of Cognition and Attention
Citation:
Melloni
L,
Van Leeuwen
S,
Alink
A and
Müller
N
(2011). Saliency maps and top-down guidance in the human brain.
Conference Abstract:
XI International Conference on Cognitive Neuroscience (ICON XI).
doi: 10.3389/conf.fnhum.2011.207.00318
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Received:
22 Nov 2011;
Published Online:
28 Nov 2011.
*
Correspondence:
Dr. Lucia Melloni, Max Planck Institute for Brain Research, Frankfurt, Germany, lucia.melloni@brain.mpg.de