Cerebral Cortex Advance Access published online on November 7, 2007
Cerebral Cortex, doi:10.1093/cercor/bhm194
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The Effects of Feature Attention on Prestimulus Cortical Activity in the Human Visual System
1 Nara Institute of Science and Technology, Graduate School of Information Science, 8916-5 Takayama-cho, Ikoma-shi, Nara 630-0101, Japan, 2 Advanced Telecommunications Research Institute International Computational Neuroscience Laboratories, 2-2-2 Hikaridai, Seika-cho, Soraku-gun, Kyoto 619-0288 Japan, 3 National Institute of Information and Communication Technology, Kobe Advanced Informations and Communications Technology Research Center, 2-2-2 Hikaridai, Seika-cho, Soraku-gun, Kyoto 691-0288, Japan, 4 National Institute for Physiological Sciences, Sensory and Cognitive Information, 38 Nishigonaka, Myoudaiji-cho, Okazaki-shi, Aichi 444-8585, Japan
Address correspondence to email: kazuhi-s{at}is.naist.jp.
Covert attention affects prestimulus activity in the visual cortex. Although most studies investigating neural mechanisms of attention have focused on the effects of spatial attention, attention can also be directed to particular features. To investigate the spatiotemporal nature of feature attention, we measured subjects’ brain activity using magnetoencephalography (MEG) and functional magnetic resonance imaging (fMRI) while subjects attended to color or motion of a stimulus based on a visual cue, which was presented 1 s before the stimulus onset. We used the hierarchical Bayesian method that allows us to estimate cortical currents with MEG and fMRI data in the order of millimeters and milliseconds. When subjects attended to color, activity within the color-sensitive area (fusiform gyrus) was selectively enhanced within the prestimulus period. By contrast, when subjects attended to motion, activity within the motion-sensitive area (middle temporal gyrus) was selectively enhanced during this period. This effect was not seen in frontal, parietal, and lower visual areas. Additionally, this effect was transient rather than sustained, suggesting that it differs from temporal aspects of spatial attention. These results suggest that, although both spatial and feature attention modulate prestimulus activity within specific visual areas, neural mechanisms underlying these effects might be different.
Key Words: color • feature attention • hierarchical Bayesian estimation • MEG • motion • preparatory activity