Sensorimotor Foundations of Cardinal and Ordinal Semantic Processing in Spatial-Numerical Associations

The spatial representation of numbers is a central focus in numerical cognition. While previous studies demonstrate that the processing of cardinal and ordinal semantics underlies spatial-numerical associations (SNAs), it remains unclear whether these two distinct semantic types share common neural representations. To address this, we employed parity judgment and magnitude classification tasks to investigate their processing patterns. Using functional magnetic resonance imaging (fMRI) alongside multivariate pattern analysis (MVPA), we revealed significant cross-task decoding between the two semantic modalities within the sensorimotor cortex. Notably, we observed a striking behavior-brain dissociation: while the behavioral Spatial-Numerical Association of Response Codes (SNARC) effect was evident solely during the implicit parity judgment task, the robust multivariate decoding of task-related dimensions within the sensorimotor cortex was predominantly observed during the explicit magnitude classification task. Rather than confirming a purely abstract spatial representation, these findings suggest a deep functional coupling between numerical evaluation and motor preparation. These results indicate that cardinal and ordinal semantic processing share overlapping neural substrates within the sensorimotor network. Ultimately, our study provides valuable neuroimaging evidence for the embodied cognition of numbers, suggesting that numerical semantics are deeply intertwined with sensorimotor and action representations.