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Numerical cognition is critical for modern life; however, the precise neural mechanisms underpinning numerical magnitude allocation in humans remain obscure. Based upon previous reports demonstrating the close behavioral and neuro-anatomical relationship between number allocation and spatial attention, we hypothesized that these systems would be subject to similar control mechanisms, namely dynamic interhemispheric competition. We employed a physiological paradigm, combining visual and vestibular stimulation, to induce interhemispheric conflict and subsequent unihemispheric inhibition, as confirmed by transcranial direct current stimulation (tDCS). This allowed us to demonstrate the first systematic bidirectional modulation of numerical magnitude toward either higher or lower numbers, independently of either eye movements or spatial attention mediated biases. We incorporated both our findings and those from the most widely accepted theoretical framework for numerical cognition to present a novel unifying computational model that describes how numerical magnitude allocation is subject to dynamic interhemispheric competition. That is, numerical allocation is continually updated in a contextual manner based upon relative magnitude, with the right hemisphere responsible for smaller magnitudes and the left hemisphere for larger magnitudes.

Original publication

DOI

10.1093/cercor/bhv344

Type

Journal article

Journal

Cereb Cortex

Publication Date

05/2016

Volume

26

Pages

2311 - 2324

Keywords

VOR, dynamic interhemispheric competition, mental number line, numerical magnitude, vestibular cognition, Adolescent, Adult, Animals, Attention, Brain, Cognition, Ear Canal, Eye Movements, Female, Frontal Lobe, Humans, Male, Mathematical Concepts, Models, Neurological, Neural Inhibition, Nystagmus, Physiologic, Physical Stimulation, Space Perception, Transcranial Direct Current Stimulation, Vision, Binocular, Young Adult