Figure 1.

Stimuli and paradigm. A, We used a multifeature visual roving standard paradigm to elicit PEs by rare changes of either color (red, green) or emotional expression (happy, fearful) of human faces (or both). This allowed us to study brain responses to stimuli that were physically identical but differed in whether color or emotion regularities were violated. Faces were presented in four peripheral quadrants of the screen. A detection task was presented at fixation at the center. Faces were reproduced with permission of the Radboud Faces Database (www.rafd.nl). B, Schematic illustration of a stimulus sequence showing transitions between stimulus types. Note physically identical stimuli taking the role of different deviant stimulus types (GH, green happy; GF, green fearful; RH, red happy; RF, red fearful faces) depending on expectations established by prior stimulus context.