title: Neural activities in V1 create the bottom-up saliency map of natural scenes.
abstract: A saliency map is the bottom-up contribution to the deployment of exogenous attention. It, as well as its underlying neural mechanism, is hard to identify because of the influence of top-down signals. A recent study showed that neural activities in V1 could create a bottom-up saliency map (Zhang et al. in Neuron 73(1):183-192, 2012). In this paper, we tested whether their conclusion can generalize to complex natural scenes. In order to avoid top-down influences, each image was presented with a low contrast for only 50 ms and was followed by a high contrast mask, which rendered the whole image invisible to participants (confirmed by a forced-choice test). The Posner cueing paradigm was adopted to measure the spatial cueing effect (i.e., saliency) by an orientation discrimination task. A positive cueing effect was found, and the magnitude of the cueing effect was consistent with the saliency prediction of a computational saliency model. In a following fMRI experiment, we used the same masked natural scenes as stimuli and measured BOLD signals responding to the predicted salient region (relative to the background). We found that the BOLD signal in V1, but not in other cortical areas, could well predict the cueing effect. These results suggest that the bottom-up saliency map of natural scenes could be created in V1, providing further evidence for the V1 saliency theory (Li in Trends Cogn Sci 6(1):9-16, 2002).
authors.affiliation: National Engineering Laboratory for Video Technology, Cooperative Medianet Innovation Center, and School of Electronics Engineering and Computer Science, Peking University, Beijing, 100871, People's Republic of China.|Key Laboratory of Machine Perception (Ministry of Education), Peking University, Beijing, 100871, People's Republic of China.
authors.forename: Cheng
authors.initials: C
authors.lastname: Chen
authors.affiliation: Laboratory of Brain and Cognition, National Institute of Mental Health, US National Institutes of Health, Bethesda, MD, 20892, USA.
authors.forename: Xilin
authors.initials: X
authors.lastname: Zhang
authors.affiliation: National Engineering Laboratory for Video Technology, Cooperative Medianet Innovation Center, and School of Electronics Engineering and Computer Science, Peking University, Beijing, 100871, People's Republic of China. Yizhou.Wang@pku.edu.cn.|Key Laboratory of Machine Perception (Ministry of Education), Peking University, Beijing, 100871, People's Republic of China. Yizhou.Wang@pku.edu.cn.
authors.forename: Yizhou
authors.initials: Y
authors.lastname: Wang
authors.affiliation: State Key Laboratory of Brain and Cognitive Science, Institute of Biophysics, Chinese Academy of Sciences, Beijing, 100101, People's Republic of China.
authors.forename: Tiangang
authors.initials: T
authors.lastname: Zhou
authors.affiliation: Key Laboratory of Machine Perception (Ministry of Education), Peking University, Beijing, 100871, People's Republic of China. ffang@pku.edu.cn.|Department of Psychology and Beijing Key Laboratory of Behavior and Mental Health, Peking-Tsinghua Center for Life Sciences, and IDG/McGovern Institute for Brain Research, Peking University, Beijing, 100871, People's Republic of China. ffang@pku.edu.cn.
authors.forename: Fang
authors.initials: F
authors.lastname: Fang
mesh_terms: D000328:Adult; D001288:Attention / Q000502:physiology*; D003463:Cues; D005260:Female; D006801:Humans; D008279:Magnetic Resonance Imaging / Q000379:methods; D008297:Male; D010364:Pattern Recognition, Visual / Q000502:physiology*; D011601:Psychophysics / Q000379:methods; D014793:Visual Cortex / Q000502:physiology*; D055815:Young Adult
keywords: Bottom-up saliency map; Natural scene; Primary visual cortex; Visual attention; fMRI