The brain mechanism underlying alphabetical order and counting processing:an ERP research

Abstract

Objective To investigate neural correlates of both order and counting processes in mental arithmetic. Methods The behavioral performance and ERP were recorded from 16 undergraduate while they were performing alphabetical order and counting tasks. A two-factor design of repeated-measure was adopted with the task (order, counting) and the distance between letters (1,2,3). The statistical parametric mapping (SPM) of both F-value and t-value was presented for ERP. Results The reaction time of the counting task was significantly slower than that of the order task and the correction rate of the former was higher than the latter ( P =0.00). Distance effects were observed for behavioral performance of the counting task. The spatiotemporal pattern of SPM suggested the right prefrontal and the left frontal-temporal regions (350～800 ms) were significantly activated under order task. The frontoparietal network (200～300 ms) was specially activated under the counting condition. The right parietal-temporal cortex at 860～890 ms showed the distance effect. Conclusion The significant activation in the right frontal and the left hemisphere under the order task suggests the functional role of the right hemisphere as retrieval and utilizing knowledge of alphabetical order, which stored in the left hemisphere. The frontoparietal network effect in the counting task suggests that the executive mechanism of working memory involved. The distance effect occurring in the left occipital and the right parietal-temporal at 860～890 ms might reflect the counting strategy and problem-size effect in mental arithmetic. Key words: Arithmetic; Ordinal processing; Counting; event-related potentials(ERP)