10The brain is constantly anticipating the future of sensory inputs based on past 11 experiences. When new sensory data is different from predictions shaped by recent 12 trends, neural signals are generated to report this surprise. Existing models for 13 quantifying surprise are based on an ideal observer assumption operating under one 14 of the three definitions of surprise set forth as the Shannon, Bayesian, and 15 Confidence-corrected surprise. In this paper, we analyze both visual and auditory 16 EEG and auditory MEG signals recorded during oddball tasks to examine which 17 temporal components in these signals are sufficient to decode the brain's surprise 18 based on each of these three definitions. We found that for both recording systems 19 the Shannon surprise is always significantly better decoded than the Bayesian 20 surprise regardless of the sensory modality and the selected temporal features used 21 for decoding. 22 squared of regression model, ERP temporal components, generative distribution, 24 decoding power, middle temporal components, late temporal components, mismatch 25 negativity (MMN), P300, oddball task 26 Author summary 27 A regression model is proposed for decoding the level of the brain's surprise in 28 response to sensory sequences using selected temporal components of recorded EEG 3 29 and MEG data. Three surprise quantification definitions (Shannon, Bayesian,and 30 Confidence-corrected surprise) are compared in offering decoding power. Four 31 different regimes for selecting temporal samples of EEG and MEG data are used to 32 evaluate which part of the recorded data may contain signatures that represent the 33 brain's surprise in terms of offering a high decoding power. We found that both the 34 middle and late components of the EEG response offer strong decoding power for 35 surprise while the early components are significantly weaker in decoding surprise. In 36 the MEG response, we found that the middle components have the highest decoding 37 power while the late components offer moderate decoding powers. When using a 38 single temporal sample for decoding surprise, samples of the middle segment possess 39 the highest decoding power. Shannon surprise is always better decoded than the 40 other definitions of surprise for all the four temporal feature selection regimes. 41 Similar superiority for Shannon surprise is observed for the EEG and MEG data 42 across the entire range of temporal sample regimes used in our analysis. 43 45 next sensory input. Past inputs are used by the brain to form prior knowledge in the 46 Bayesian brain model [2,3]. In fact, the results of brain functions such as perception, 47 eliminating ambiguity, attention, and decision making are dependent on the way the 48 current sensory input and the knowledge gained from previous experiences are 49 combined in the hierarchical inference model of the brain [1] (for review see [4]).
50An input different from what the brain has predicted will be surprising in that it 51 generates a form of response measurable by brain ...