Figure 3.
Regressors included in the statistical analysis of fMRI data. The main GLM included three categorical and three parametric regressors (see Materials and Methods, General linear model 1: main fMRI data statistical analysis). The three categorical regressors modeled the main steps of perceptual decision making: sensory processing, decision-related activity and motor response. Three parametric regressors were derived from the decision-related regressors and hierarchically orthogonalized. These parametric regressors modeled the modulation of BOLD activity at the time of decision by the surprise and the predictive information conveyed by the last and the penultimate shape.