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Identifying natural images from human brain activity


A challenging goal in neuroscience is to be able to read out, or decode, mental content from brain activity. Recent functional magnetic resonance imaging (fMRI) studies have decoded orientation1,2, position3 and object category4,5 from activity in visual cortex. However, these studies typically used relatively simple stimuli (for example, gratings) or images drawn from fixed categories (for example, faces, houses), and decoding was based on previous measurements of brain activity evoked by those same stimuli or categories. To overcome these limitations, here we develop a decoding method based on quantitative receptive-field models that characterize the relationship between visual stimuli and fMRI activity in early visual areas. These models describe the tuning of individual voxels for space, orientation and spatial frequency, and are estimated directly from responses evoked by natural images. We show that these receptive-field models make it possible to identify, from a large set of completely novel natural images, which specific image was seen by an observer. Identification is not a mere consequence of the retinotopic organization of visual areas; simpler receptive-field models that describe only spatial tuning yield much poorer identification performance. Our results suggest that it may soon be possible to reconstruct a picture of a person’s visual experience from measurements of brain activity alone.

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Figure 1: Schematic of experiment.
Figure 2: Receptive-field model for a representative voxel.
Figure 3: Identification performance.
Figure 4: Factors that impact identification performance.


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This work was supported by a National Defense Science and Engineering Graduate fellowship (K.N.K.), the National Institutes of Health, and University of California, Berkeley intramural funds. We thank B. Inglis for assistance with MRI, K. Hansen for assistance with retinotopic mapping, D. Woods and X. Kang for acquisition of whole-brain anatomical data, and A. Rokem for assistance with scanner operation. We also thank C. Baker, M. D’Esposito, R. Ivry, A. Landau, M. Merolle and F. Theunissen for comments on the manuscript. Finally, we thank S. Nishimoto, R. Redfern, K. Schreiber, B. Willmore and B. Yu for their help in various aspects of this research.

Author Contributions K.N.K. designed and conducted the experiment and was first author on the paper. K.N.K. and T.N. analysed the data. R.J.P. provided mathematical ideas and assistance. J.L.G. provided guidance on all aspects of the project. All authors discussed the results and commented on the manuscript.

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Correspondence to Jack L. Gallant.

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This file contains Supplementary Figures 1-11 with Legends, Supplementary Table 1, Supplementary Discussion, Supplementary Methods, and Supplementary Notes with additional references. (PDF 3551 kb)

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Kay, K., Naselaris, T., Prenger, R. et al. Identifying natural images from human brain activity. Nature 452, 352–355 (2008).

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