(A) Coefficients of all 1,705 categories in the first group PC, organized according to the graphical structure of WordNet. Links indicate "is a" relationships (e.g., an athlete is a person); some relationships used in the model have been omitted for clarity. Each marker represents a single noun (circle) or verb (square). Red markers indicate positive coefficients and blue indicates negative coefficients. The area of each marker indicates the magnitude of the coefficient. This PC distinguishes between categories with high stimulus energy (e.g., moving objects like "person" and "'vehicle'") and those with low stimulus energy (e.g., stationary objects like "sky" and "city").
(B) The three-dimensional RGB colormap used to visualize PCs 2-4. The category coefficient in the second PC determined the value of the red channel, the third PC determined the green channel, and the fourth PC determined the blue channel. Under this scheme, categories that are represented similarly in the brain are assigned similar colors. Categories with zero coefficients appear neutral gray.
(C) Coefficients of all 1,705 categories in group PCs 2-4, organized according to the WordNet graph. The color of each marker is determined by the RGB colormap in (B). Marker sizes reflect the magnitude of the three-dimensional coefficient vector for each category. This graph shows that categories thought to be semantically related (e.g., "athletes" and "walking") are represented similarly in the brain.