The zero effect: voxel-based lesion symptom mapping of number transcoding errors following stroke

Marleen Haupt,Céline R Gillebert,Nele Demeyere

doi:10.1038/s41598-017-08728-x

Abstract

Zero represents a special case in our numerical system because it is not represented on a semantic level. Former research has shown that this can lead to specific impairments when transcoding numerals from dictation to written digits. Even though, number processing is considered to be dominated by the left hemisphere, studies have indicated that both left as well as right hemispheric stroke patients commit errors when transcoding numerals including zeros. Here, for the first time, a large sample of subacute stroke patients (N = 667) was assessed without being preselected based on the location of their lesion, or a specific impairment in transcoding zero. The results show that specific errors in transcoding zeros were common (prevalence = 14.2%) and a voxel-based lesion symptom mapping analysis (n = 153) revealed these to be related to lesions in and around the right putamen. In line with former research, the present study argues that the widespread brain network for number processing also includes subcortical regions, like the putamen with connections to the insular cortex. These play a crucial role in auditory perception as well as attention. If these areas are lesioned, number processing tasks with higher attentional and working memory loads, like transcoding zeros, can be impaired.

Highlights

The concept of zero is considered to be a great achievement of humankind
Within the transcoding of complex numerals, the production of the numeral zero represents a special case because it is not represented on the semantic level[5]
In line with the lexical-semantic model, a patient with left cerebrovascular damage was found to have difficulties writing complex numerals containing syntactic zeros (e.g. 807) while no difficulties emerged from numerals with lexical zeros (e.g. 80)[5]. This finding confirms former neuropsychological studies reporting errors in transcoding zeros in small samples consisting of only left hemispheric patients[6, 7]. These studies are in accordance with a long line of number processing research stating that the left hemisphere, especially the left parietal lobe, plays an important role in number processing[8,9,10,11,12]

Summary

Introduction

The concept of zero is considered to be a great achievement of humankind. Even though positive numbers still represent an abstract concept, they correspond to and represent entities in real life. The abstract semantic representation subsequently activates the appropriate lexical and syntactic production system This is realised by planning a frame containing the appropriate number of slots in which the digits, corresponding to the basic values, can be inserted[2]. In line with the lexical-semantic model, a patient with left cerebrovascular damage was found to have difficulties writing complex numerals containing syntactic zeros (e.g. 807) while no difficulties emerged from numerals with lexical zeros (e.g. 80)[5]. This finding confirms former neuropsychological studies reporting errors in transcoding zeros in small samples consisting of only left hemispheric patients[6, 7]. The parietal areas were found to be significantly involved in processing the magnitude of numerical information

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