The P3b differentiates parallel physical and rule-based updating of a sensory model

The capacity to form and update mental representations of the type and timing of sensory events is a central tenet of adaptive behavior in a dynamically changing environment. An internal model of stimulus contingencies provides a means to optimize behavior through predictive adjustments based on past to future events. To this end, neural and cognitive processes rely on systematic relations between events and use these rules to optimize information processing. The P3 complex of the event-related potential of the electroencephalogram (ERP/EEG) is a well-established and extensively tested index of such mechanisms. Here we investigated the P3b sensitivity to auditory stimulus deviations associated with two updating operations: physical change (switching stimulus pitches) and rule change (switching additive and subtractive target stimulus counting). Participants listened to a variant of the classical oddball sequence consisting of frequent standard (600 Hz) and two equally probable less frequent deviant tones (660 Hz, 540 Hz), keeping count of the deviant tones and switching between addition and subtraction with a pitch change. The results indicate specific amplitude modulations, confirming the P3b as a context-sensitive marker of physical and cognitive components of an internal model. This suggests that the P3b can be used as a differential marker of predictive coding mechanisms.