Neural encoding of symbolic, non-symbolic, and embodied non-symbolic numerical information in young and older adults

Numeracy has important implications across the lifespan, and age-related decline in this ability represents a vulnerability factor for older adults in managing everyday tasks, yet its mechanisms remain poorly understood. This study employed a parity judgment task to examine age-related differences in basic numerical representation in younger and older adults using three stimulus types: Arabic digits (symbolic), dot arrays (non-symbolic), and finger configurations (embodied non-symbolic), to capture the multiple representational formats supporting numeracy. Sixty healthy participants (31 young adults, 25.3 ± 4.83 years; 29 older adults, 69.8 ± 4.53 years) completed the task while EEG was recorded. Response latency and accuracy were measured, and neural correlates of numerical processing were analyzed, focusing on P1 and N1 components at parieto-occipital sites. Multivariate pattern analysis assessed differences in EEG responses across numerical formats. Accuracy was high and did not differ reliably by age or stimulus type, whereas reaction times were influenced by both age and stimulus type. Early ERP components were sensitive to stimulus format, with dot arrays eliciting longer N1 latency and lower P1 amplitude. Age further prolonged N1 latency and interacted with stimulus format on N1 amplitude, with reduced responses to finger configurations in young adults. MVPA analyses showed that the neural correlates supporting symbolic, non-symbolic, and embodied non-symbolic numerical representations are distinct, suggesting reliance on separate neural processes. Overall, this study offers a comprehensive account of how different forms of numerical information are represented in the aging brain, highlighting the multifaceted and age-sensitive nature of numerical reasoning.