Experimental Brain Research

, Volume 236, Issue 4, pp 1129–1138 | Cite as

The neural circuits of number and letter copying: an fNIRS study

  • Christina Artemenko
  • Andra Coldea
  • Mojtaba Soltanlou
  • Thomas Dresler
  • Hans-Christoph Nuerk
  • Ann-Christine Ehlis
Research Article

Abstract

In our daily lives, we are constantly exposed to numbers and letters. However, it is still under debate how letters and numbers are processed in the brain, while information on this topic would allow for a more comprehensive understanding of, for example, known influences of language on numerical cognition or neural circuits shared by numerical cognition and language processing. Some findings provide evidence for a double dissociation between numbers and letters, with numbers being represented in the right and letters in the left hemisphere, while the opposing view suggests a shared neural network. Since processing may depend on the task, we address the reported inconsistencies in a very basic symbol copying task using functional near-infrared spectroscopy (fNIRS). fNIRS data revealed that both number and letter copying rely on the bilateral middle and left inferior frontal gyri. Only numbers elicited additional activation in the bilateral parietal cortex and in the left superior temporal gyrus. However, no cortical activation difference was observed between copying numbers and letters, and there was Bayesian evidence for common activation in the middle frontal gyri and superior parietal lobules. Therefore, we conclude that basic number and letter processing are based on a largely shared cortical network, at least in a simple task such as copying symbols. This suggests that copying can be used as a control condition for more complex tasks in neuroimaging studies without subtracting stimuli-specific activation.

Keywords

Number processing Letter processing Copying task fNIRS 

Notes

Acknowledgements

This research was supported by the LEAD Graduate School & Research Network (GSC1028), which is funded within the framework of the Excellence Initiative of the German federal and state governments. This research was further funded by a Grant from the Science Campus Tübingen, project 8.4 to HCN supporting MS. MS was also supported by the DFG Grant (NU 265/3-1) to HCN. ACE was partly supported by the IZKF Tübingen (Junior Research Group, Grant 2115-0-0). We would like to thank Minako Uga and Ippeita Dan for their help in preparing the spatial registration and anatomical labeling of fNIRS channels. We would also like to thank our research assistants for their help in data collection and language proofreading of the manuscript.

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Copyright information

© Springer-Verlag GmbH Germany, part of Springer Nature 2018

Authors and Affiliations

  1. 1.LEAD Graduate School & Research NetworkUniversity of TübingenTübingenGermany
  2. 2.Department of PsychologyUniversity of TübingenTübingenGermany
  3. 3.School of PsychologyUniversity of GlasgowGlasgowUK
  4. 4.Graduate Training Centre of Neuroscience/IMPRS for Cognitive and Systems NeuroscienceTübingenGermany
  5. 5.Leibniz-Institut für WissensmedienTübingenGermany
  6. 6.Department of Psychiatry and PsychotherapyUniversity of TübingenTübingenGermany

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