max 150 words) 14Predictive coding suggests that the brain infers the causes of its sensations by combining sensory 15 evidence with internal predictions based on available prior knowledge.However, the 16 neurophysiological correlates of (pre-)activated prior knowledge serving for predictions are still 17 unknown. Based on the idea that such pre-activated prior-knowledge must be maintained until 18 needed we measured the amount of maintained information in neural signals via the active 19 information storage (AIS) measure. AIS was calculated on whole-brain beamformer-reconstructed 20 source time-courses from magnetoencephalography recordings of 52 human subjects during the 21 baseline of a Mooney face/house detection task. Pre-activation of prior knowledge for faces 22 showed as alpha-and beta-band related AIS increases in content specific areas; these AIS 23 increases were behaviourally relevant. Moreover, top-down transfer of predictions estimated by 24 transfer entropy was associated with beta frequencies. Our results support accounts that activated 25 prior knowledge and the corresponding predictions are signalled in low frequency activity (<30 Hz). 26 Acknowledgements: 27ABG received support by Ernst Ludwig Ehrlich Studienwerk (BMBF scholarship for graduate 28 students). GFP received support by Villigst Studienwerk (BMBF scholarship for graduate students). ). Predictive 35coding theory proposes that the brain constantly makes inferences about the state of the outside 36 world. This is supposed to be accomplished by building hierarchical internal predictions based on 37 2 prior knowledge which are compared to incoming information at each level of the cortical hierarchy 38 in order to continuously adapt and update these internal models (Mumford, 1992; Rao et al., 1999; 39 Friston, 2005Friston, , 2010 40The postulated use of predictions for inference requires several preparatory steps: First, task 41 relevant prior knowledge passively stored in synaptic weights needs to be transferred into activated 42 prior knowledge, i.e. information represented in neural activity in order to make this knowledge 43 available to other parts of the brain (see Zipser et al., 1993 for a distinction of active and passive 44 storage). Subsequently, (pre-)activated prior knowledge needs to be maintained until needed and 45 to be constantly transferred as a prediction in top-down direction to a lower area of the cortical 46 hierarchy, where it will be matched with the incoming information (e.g. Mumford, 1992; Friston, 47 2005 Friston, 47 , 2010. 48With respect to the neural correlates of activated prior knowledge and predictions we know that the 49 prediction of specific features or object categories increases fMRI BOLD activity in the brain region 50 at which the feature or category is usually processed (Puri et al., 2009; Esterman and Yantis, 2009; 51 Kok et al., 2014). However, only little is known about how the maintenance of pre-activated prior 52 knowledge and the corresponding transfer of predictions are actuall...

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