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Discrepancy between repetition suppression and pattern analysis provides new insights into the role of M1 and parietal areas in sequence learning

How does the brain change during skill learning? We previously conducted a longitudinal fMRI motor sequence learning study and, using multivariate techniques, found learning-related changes in premotor and parietal areas, but not in the primary motor cortex (M1) (1). However, a study using repetition suppression (RS) had previously suggested that M1 represents learned sequences. Here we replicate this discrepancy in a single experiment, allowing us to investigate the differences between RS and multivariate pattern analysis in detail. We found that the RS effect in M1 and parietal areas reflect fundamentally different processes. M1’s activity represents the starting finger of the sequence, an effect that vanishes with repetition. In contrast, activity patterns in parietal areas exhibit sequence dependency, which persists with repetition. These findings demonstrate that combining RS and pattern analysis can provide novel functional insights, here specifically into the relative contribution of cortical motor areas to sequence production.