Distinct Representations of Magnitude and Spatial Position within Parietal Cortex during Number–Space Mapping

Abstract

Mapping numbers onto space is foundational to mathematical cognition. These cognitive operations are often conceptualized in the context of a "mental number line" and involve multiple brain regions in or near the intraparietal sulcus (IPS) that have been implicated both in numeral and spatial cognition. Here we examine possible differentiation of function within these brain areas in relating numbers to spatial positions. By isolating the planning phase of a number line task and introducing spatiotopic mapping tools from fMRI into mental number line task research, we are able to focus our analysis on the neural activity of areas in anterior IPS (aIPS) previously associated with number processing and on spatiotopically organized areas in and around posterior IPS (pIPS), while participants prepare to place a number on a number line. Our results support the view that the nonpositional magnitude of a numerical symbol is coded in aIPS, whereas the position of a number in space is coded in posterior areas of IPS. By focusing on the planning phase, we are able to isolate activation related to the cognitive, rather than the sensory-motor, aspects of the task. Also, to allow the separation of spatial position from magnitude, we tested both a standard positive number line (0 to 100) and a zero-centered mixed number line (-100 to 100). We found evidence of a functional dissociation between aIPS and pIPS: Activity in aIPS was associated with a landmark distance effect not modulated by spatial position, whereas activity in pIPS revealed a contralateral preference effect.

A distinction between working memory components as unique predictors of mathematical components in 7–8 year old children

“…In contrast, we see a stronger influence of visuospatial working memory in components of mathematics with a clear visual element: understanding shape and handling data. This is also in line with evidence indicating that different brain areas are activated in tasks requiring the manipulation of number or space (Arsalidou & Taylor, 2011;Kanayet et al, 2018).…”

Automatic Processing of Numerosity in Human Neocortex Evidenced by Occipital and Parietal Neuromagnetic Responses

“…Our results thus support the existence of a dedicated coding for numerosity both in parietal and occipital regions even in case of sequential presentation of the stimuli. This corroborates evidence of a functional dissociation between magnitude and spatial coding of numerosity among the intraparietal regions ( Kanayet et al. 2018 ), showing that neither numerosity nor continuous magnitude coding can be reduced to sole spatial coding.…”

Moving attention along the mental number line in preschool age: Study of the operational momentum in 3‐ to 5‐year‐old children's non‐symbolic arithmetic

“…Similar conclusion comes also from Knops, Dehaene, Berteletti, and Zorzi (2014) study. Recent neuroimaging studies also point to the divergence of brain underpinnings of the magnitude and spatial aspects of number representations (Fattorini, Pinto, Merola, D’Onofrio, & Doricchi, 2016; Kanayet et al., 2018). Acquisition of exact symbolic (verbal) numerical representations with explicit ordering relationships may be an important factor that remodels the process of numerical space construction, which may also project on non‐symbolic numerical processes (see Berteletti et al., 2010; Piazza et al., 2013; Sella, Lucangeli, & Zorzi, 2018; cf.…”