Effective Connectivity of the Multiplication Network: A Functional MRI and Multivariate Granger Causality Mapping Study

• Authors: Frank Krueger, George Mason University; Steffen Landgraf, Humboldt University; Elke van der Meer, Humboldt University; Gopikrishna Deshpande, Georgia Institute of Technology; Xiaoping Hu, Emory University
• Journal Title: Human Brain Mapping
• Volume: Volume 32, Number 9
• Publisher: Wiley | 2011-09-01, Pages 1419-1431
• Type of Work: Article | Final Publisher PDF
• Publisher DOI: http://doi.org/10.1002/hbm.21119
• Subjects: Biology, Neuroscience; Health Sciences, Radiology; Engineering, Biomedical
• Keywords: Science & Technology; Life Sciences & Biomedicine; Neurosciences; Neuroimaging; Radiology, Nuclear Medicine & Medical Imaging; Neurosciences & Neurology; calculation; connectivity; dorsolateral prefrontal cortex; intraparietal sulcus; mathematical competence; Granger causality; Directed transfer function; Mental calculation; Parietal cortex; Number representation; Mathematical modeling; Cortical activation; Cerebral networks; Brain; FMRI

Abstract

Developmental neuropsychology and functional neuroimaging evidence indicates that simple and complex mental calculation is subserved by a fronto-parietal network. However, the effective connectivity (connection direction and strength) among regions within the fronto-parietal network is still unexplored. Combining event-related fMRI and multivariate Granger Causality Mapping (GCM), we administered a multiplication verification task to healthy participants asking them to solve single and double-digit multiplications. The goals of our study were first, to identify the effective connectivity of the multiplication network, and second, to compare the effective connectivity patterns between a low and a high arithmetical competence (AC) group. The manipulation of multiplication difficulty revealed a fronto-parietal network encompassing bilateral intraparietal sulcus (IPS), left pre-supplementary motor area (PreSMA), left precentral gyrus (PreCG), and right dorsolateral prefrontal cortex (DLPFC). The network was driven by an intraparietal IPS-IPS circuit hosting a representation of numerical quantity intertwined with a fronto-parietal DLPFC-IPS circuit engaged in temporary storage and updating of arithmetic operations. Both circuits received additional inputs from the PreCG and PreSMA playing more of a supportive role in mental calculation. The high AC group compared to the low AC group displayed a greater activation in the right IPS and based its calculation more on a feedback driven intraparietal IPS-IPS circuit, whereas the low competence group more on a feedback driven fronto-parietal DLPFC-IPS circuit. This study provides first evidence that multivariate GCM is a sensitive approach to investigate effective connectivity of mental processes involved in mental calculation and to compare group level performances for different populations.