BEYOND BLOBOLOGY

Brain decoding took off about a decade ago1, when neuroscientists realized that there was a lot of untapped information in the brain scans they were producing using functional magnetic resonance imaging (fMRI). That technique measures brain activity by identifying areas that are being fed oxygenated blood, which light up as coloured blobs in the scans. To analyse activity patterns, the brain is segmented into little boxes called voxels — the three-dimensional equivalent of pixels — and researchers typically look to see which voxels respond most strongly to a stimulus, such as seeing a face. By discarding data from the voxels that respond weakly, they conclude which areas are processing faces.
Decoding techniques interrogate more of the information in the brain scan. Rather than asking which brain regions respond most strongly to faces, they use both strong and weak responses to identify more subtle patterns of activity. Early studies of this sort proved, for example, that objects are encoded not just by one small very active area, but by a much more distributed array.