Compressed representations underpin knowledge awareness in sequence learning

Humans can acquire sequence structure before its presence enters awareness, and in some learners this implicit knowledge later becomes accessible and reportable. Yet the neural reformatting that enables this transition remains unclear. Here we used electro/magnetoencephalography (EEG/MEG) to resolve how category-based triplet rules were organized before and after awareness emerged. We found that implicit sequence knowledge was already represented in an abstract, compressed format. Within this format, rule information generalized across triplet elements, and regular-sequence elements became more similar while perceptual-category structure remained separable. Compression rate quantified how efficiently local rule information entered this shared format, and its pre-awareness level predicted later awareness specifically in the event-related potential P3 window. MEG source imaging localised pre-transition compression to left middle temporal cortex and showed post-awareness expansion into prefrontal cortex. Pre-awareness directional connectivity further showed that temporal-to-prefrontal theta-band transfer was rule-specific and predicted later awareness. Overall, these findings identify a mechanism supporting conscious access to abstract sequence-rule knowledge, involving cross-element representational compression and theta-band routing from the compression source to prefrontal cortex.