Abstract
Multicultural environments require learning multiple number notations wherein some are encountered more frequently than others. This leads to differences in exposure and consequently differences in usage between notations. We find that differential notational usage imposes a significant neurocognitive load on number processing. Despite simultaneous acquisition, twenty four adult binumerates, familiar with two positional writing systems namely Hindu Nagari digits and Hindu Arabic digits, reported significantly lower preference and usage for Nagari as compared to Arabic. Twenty-four participants showed significantly increased reaction times and reduced accuracy while performing magnitude comparison tasks in Nagari with respect to Arabic. Functional magnetic resonance imaging revealed that processing Nagari elicited significantly greater activity in number processing and attention networks. A direct subtraction of networks for Nagari and Arabic notations revealed a neural circuit comprising of bilateral Intra-parietal Sulcus (IPS), Inferior and Mid Frontal Gyri, Fusiform Gyrus and the Anterior Cingulate Cortex (FDR p < 0.005). Additionally, whole brain correlation analysis showed that activity in the left inferior parietal region was modulated by task performance in Nagari. We attribute the increased activation in Nagari to increased task difficulty due to infrequent exposure and usage. Our results reiterate the role of left IPS in modulating performance in numeric tasks and highlight the role of the attention network for monitoring symbolic notation mode in binumerates.
Highlights
Numbers are an integral part of life and are represented as distinct symbolic notations across varying cultural environments
This was followed by an inclusive masking by activation maps from identification tasks for each notation in order to control for the areas activated by cognitive factors other than number processing such as button press
The current study assessed the effect of notation usage on task performance in Ng-Ar binumerates performing numerical magnitude comparison in two symbolic notations namely Nagari and Arabic
Summary
Numbers are an integral part of life and are represented as distinct symbolic notations across varying cultural environments. Electrophysiology studies in primates and neuro-stimulation research have implicated areas in the pre-frontal cortex with spatial representation of numbers (Rusconi et al, 2011), in creating associations between numerical symbols and numerical representations (Diester and Nieder, 2007) as well as in the encoding of mathematical rules (Bongard and Nieder, 2010). A substantial body of research over the last two decades has demonstrated the universality of activation of the IPS, pre-frontal regions and ventral visual areas in tasks involving number processing. The study by Wu et al (2009) found increased activations in the pre-frontal areas while processing Roman numerals as compared to Ar
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