We asked how many distinct common response-tuning functions are needed to contain the information that DNA Damage inhibitor affords the full range of fine-grained distinctions among complex, visual stimuli. We tested the sufficiency of lower-dimensional subspaces and found that BSC accuracies continued to increase with more than 20 common response-tuning functions. We present a 35-dimensional common model space that afforded BSC for all three

experiments at levels of accuracy that were equivalent to BSC with all 1,000 hyperaligned dimensions or WSC with 1,000 voxels. Ten dimensions were sufficient within the limited stimulus domains of each category perception experiment, but these sets of ten dimensions did not Erastin price afford high levels of BSC for the other experiment or for the movie. Thus, these lower-dimensional models are subspaces of the full model and are valid only for more limited stimulus domains. Hyperalignment uses the Procrustean transformation to rotate and reflect the coordinate axes for an individual’s voxel space into a common coordinate system in which the response vectors

for the same stimuli or events are in optimal alignment across subjects. Principal components analysis is then used to rotate the common space into a new coordinate system that is ordered by variance accounted for, and the common space is reduced to the top components that afford high levels of BSC. This procedure produces a parameter matrix for each subject

that transforms that subject’s data into model space coordinates (bottom square in Figure 1; Figure S1A). The parameter matrix for each subject can be applied to transform a different set of response-pattern vectors, using the same voxels in that subject, into the common model space (Figure S1B). This step models the patterns of response to new stimulus conditions as weighted sums of the same basis patterns that model the responses to stimuli that were used to develop the common space. In our principal analysis, model dimensions were defined by common differential responses to time points in the movie. Rotating the response-pattern vectors for the category perception experiments Oxalosuccinic acid into these dimensions afforded BSC of those categories at levels of accuracy that are equivalent to WSC and allowed us to further characterize the response-tuning profiles for model dimensions in terms of differential responses to specific categories of faces, objects, and animals. The columns in each subject’s hyperalignment parameters contain information about the topographic patterns for each model dimension in the form of voxel weights that can be displayed as brain images (Figure 6B; Figure S1C). Patterns of response to single stimuli or time points are modeled as weighted sums of these patterns (Figure S1D).