This is fMRI data from Kamitani Y and Tong F (2005): Decoding the visual and subjective contents of the human brain. Nature 8, pp 679-685. This paper explored the ability to decode the perception of edge orientation in four human subjects using an orientation decoder.
The figure above shows: (a) the orientation decoder that takes as input data from fmri voxels, and outputs a predicted orientation for a stimulus, and (b) shows the orientation selectivity of individual voxels and detectors.
Four human subjects viewed contrast-based oriented image gratings with 8 possible grating orientations. Each subject performed 20-24 trials, for 20-24 trials per grating orientation.
Voxels from V1, V2, V3, V4, and VP cortex are shared in this data.