Distinct representations of numerical and non-numerical order in the human intraparietal sulcus revealed by multivariate pattern recognition

Marco Zorzi, Maria Grazia Di Bono, Wim Fias

Research output: Contribution to journalArticle

Abstract

Neuroimaging studies of numerical cognition have pointed to the horizontal segment of the intraparietal sulcus (hIPS) as the neural correlate of numerical representations in humans. However, the specificity of hIPS for numbers remains controversial. For example, its activation during numerical comparison cannot be distinguished from activation during ordinal judgments on non-numerical sequences such as letters (Fias et al., 2007, J. Neuroscience). Based on the hypothesis that the fine-grained distinction between representations of numerical vs. letter order in hIPS might simply be invisible to conventional fMRI data analysis, we used support vector machines (SVM) to reanalyse the data of Fias et al. (2007). We show that classifiers trained on hIPS voxels can discriminate between number comparison and letter comparison, even though the two tasks produce the same metric of behaviour. Voxels discriminating between the two conditions were consistent across subjects and contribution analysis revealed maps of distinct sets of voxels implicated in the processing of numerical vs. alphabetical order in bilateral hIPS. These results reconcile the neuroimaging data with the neuropsychological evidence suggesting dissociations between numbers and other non-numerical ordered sequences, and demonstrate that multivariate analyses are fundamental to address fine-grained theoretical issues with fMRI studies.

Original languageEnglish
Pages (from-to)674-680
Number of pages7
JournalNeuroImage
Volume56
Issue number2
DOIs
Publication statusPublished - May 15 2011

Keywords

  • Numerical cognition
  • Ordered sequences
  • Ordinal meaning
  • Support vector machines

ASJC Scopus subject areas

  • Cognitive Neuroscience
  • Neurology

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