Figure 4.

Parametrically estimated responses of the central region from Experiment 1. BOLD signal change is plotted as a function of the number of coactive border regions. UF corresponds to the response in unifocal condition with no surround stimulation, and the 1, 2, and 3 correspond to the number of coactive border regions in multifocal condition. Responses are reconstructed from coefficient estimates of the parametric model (see Quantification of responses in the Methods section), and averaged over the voxels in the central region. Dashed lines denote the standard deviation of estimates within a cluster. Suppression is evident in all subjects as expected from the significant negative linear coefficient of border interactions. The positive quadratic coefficient was significant for subjects 2, 5, 6, and 8, and can be seen here as the saturation of the suppression strength after two coactive border regions.