Symbols Are Special: An fMRI Adaptation Study of Symbolic, Nonsymbolic, and Non-Numerical Magnitude Processing in the Human Brain.

H Moriah Sokolowski,Lien Peters,Daniel Ansari,Zachary Hawes

doi:10.1093/texcom/tgab048

Abstract

How are different formats of magnitudes represented in the human brain? We used functional magnetic resonance imaging adaptation to isolate representations of symbols, quantities, and physical size in 45 adults. Results indicate that the neural correlates supporting the passive processing of number symbols are largely dissociable from those supporting quantities and physical size, anatomically and representationally. Anatomically, passive processing of quantities and size correlate with activation in the right intraparietal sulcus, whereas symbolic number processing, compared with quantity processing, correlates with activation in the left inferior parietal lobule. Representationally, neural patterns of activation supporting symbols are dissimilar from neural activation patterns supporting quantity and size in the bilateral parietal lobes. These findings challenge the longstanding notion that the culturally acquired ability to conceptualize symbolic numbers is represented using entirely the same brain systems that support the evolutionarily ancient system used to process quantities. Moreover, these data reveal that regions that support numerical magnitude processing are also important for the processing of non-numerical magnitudes. This discovery compels future investigations of the neural consequences of acquiring knowledge of symbolic numbers.

Highlights

As a species, humans are unique in our ability to represent numerical magnitudes symbolically (e.g., “3” or “three”)
The goal of the current study was to examine whether the uniquely human capacity to process symbolic numerical magnitudes relies on the same brain regions that support the processing of nonsymbolic numerical magnitudes and/or non-numerical magnitudes
The findings from the current study suggest that activation in the left parietal lobule is specific to symbolic number processing, whereas the right intraparietal sulcus is activated during nonsymbolic magnitude processing and potentially to a lesser degree during symbolic numerical magnitude processing (Sokolowski, Fias, Mousa, et al 2017)

Summary

Introduction

Humans are unique in our ability to represent numerical magnitudes symbolically (e.g., “3” or “three”). Brain regions associated with numerical magnitude processing are activated during the processing of non-numerical magnitudes such as physical size, duration, and luminance (Walsh 2003; Cohen Kadosh et al 2008; Cantlon et al 2009b; Sokolowski, Fias, Ononye, et al 2017). This finding of common brain regions supporting numerical and non-numerical magnitude processing has been taken to suggest that the common brain regions used to process both symbolic and nonsymbolic numerical magnitudes (often referred to as an abstract number processing system) may be a general system used to process both numerical and non-numerical magnitudes. The question of whether symbolic and nonsymbolic numerical magnitudes are processed using the same brain regions while controlling for brain regions associated with nonnumerical magnitude processing must still be addressed

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