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Hum Brain Mapp. 2017 Jun;38(6):3210-3225. doi: 10.1002/hbm.23585. Epub 2017 Mar 27.

The functional architectures of addition and subtraction: Network discovery using fMRI and DCM.

Yang Y1,2,3,4, Zhong N1,2,5,3,4, Friston K6, Imamura K7, Lu S1,5,3,4, Li M1,5,3,4, Zhou H1,5,3,4, Wang H1,5,3,4, Li K4,8, Hu B9.

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Beijing Advanced Innovation Center for Future Internet Technology, Beijing University of Technology, Beijing, China.
Department of Life Science and Informatics, Maebashi Institute of Technology, Maebashi, Japan.
Beijing International Collaboration Base on Brain Informatics and Wisdom Services, Beijing, China.
Beijing Key Laboratory of MRI and Brain Informatics, Beijing, China.
International WIC Institute, Beijing University of Technology, Beijing, China.
The Wellcome Trust Centre for Neuroimaging, University College London, London, UK.
Department of Systems Life Engineering, Maebashi Institute of Technology, Maebashi, Japan.
Department of Radiology, Xuanwu Hospital, Capital Medical University, Beijing, China.
Ubiquitous Awareness and Intelligent Solutions Lab, Lanzhou University, Lanzhou, China.


The neuronal mechanisms underlying arithmetic calculations are not well understood but the differences between mental addition and subtraction could be particularly revealing. Using fMRI and dynamic causal modeling (DCM), this study aimed to identify the distinct neuronal architectures engaged by the cognitive processes of simple addition and subtraction. Our results revealed significantly greater activation during subtraction in regions along the dorsal pathway, including the left inferior frontal gyrus (IFG), middle portion of dorsolateral prefrontal cortex (mDLPFC), and supplementary motor area (SMA), compared with addition. Subsequent analysis of the underlying changes in connectivity - with DCM - revealed a common circuit processing basic (numeric) attributes and the retrieval of arithmetic facts. However, DCM showed that addition was more likely to engage (numeric) retrieval-based circuits in the left hemisphere, while subtraction tended to draw on (magnitude) processing in bilateral parietal cortex, especially the right intraparietal sulcus (IPS). Our findings endorse previous hypotheses about the differences in strategic implementation, dominant hemisphere, and the neuronal circuits underlying addition and subtraction. Moreover, for simple arithmetic, our connectivity results suggest that subtraction calls on more complex processing than addition: auxiliary phonological, visual, and motor processes, for representing numbers, were engaged by subtraction, relative to addition. Hum Brain Mapp 38:3210-3225, 2017.


arithmetic processing; dynamic causal modeling; fMRI; network discovery

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