Accumulation of non‐numerical evidence during nonsymbolic number processing in the brain: An fMRI study

Abstract

Behavioral evidence has shown that when performing a nonsymbolic number comparison task (e.g., deciding which of two dot arrays contains more dots), participants' responses are sensitive to affected by both numerical (e.g., number of items) and non-numerical magnitudes (i.e., area, density, etc.). Thus far it is unclear what brain circuits support this process of accumulating non-numerical variables during nonsymbolic number processing. To investigate this, 21 adult participants were asked to engage in a dot comparison task. To measure the neural correlates of accumulating numerical and non-numerical variables, we manipulated the number of the non-numerical magnitudes that were congruent (correlated with number) or incongruent (anticorrelated with number). In a control task, participants were asked to choose the darker of two gray rectangles (brightness task). The tasks were matched in terms of their difficulty. The results of a whole brain analysis for regions sensitive to the congruity of numerical and non-numerical magnitudes revealed a region in the right inferior frontal gyrus (rIFG). Activation in this region was found to be correlated with the relative congruency of numerical and non-numerical magnitudes. In contrast, this region was not modulated by difficulty of the brightness control task. Accordingly in view of these findings, we suggest that the rIFG supports the accumulation of non-numerical magnitudes that are positively correlated with number. Therefore taken together, this study reveals a brain region whose pattern of activity is influenced by the congruency between numerical and non-numerical variables during nonsymbolic number judgments. Hum Brain Mapp 38:4908-4921, 2017. © 2017 Wiley Periodicals, Inc.

Neurodevelopmental differences in child and adult number processing: An fMRI-based validation of the triple code model

“…The conjunction of contrasts [Arabic > Control ∩ Verbal > Control ∩ Nonsymbolic > Control] resulted in a single cluster of suprathreshold activity in the right lingual gyrus (subdivision hOc2). Leibovich and Ansari (2017) have implicated this region as one of five clusters in a bilateral occipito-parietal network, found to be more active during numerosity comparisons than brightness comparisons, suggesting low-level visual selectivity for numerical magnitude stimuli across all three representational codes of the TCM (cf. Skagenholt et al, 2018 ).…”

Independent adaptation mechanisms for numerosity and size perception provide evidence against a common sense of magnitude

“…This effect can also act in the opposite direction, with size judgments influenced by numerosity 16 . Interactions between numerosity and other magnitudes have also been demonstrated by electroencephalography 17 , 18 and imaging techniques 19 . However, questions remain open: do system interactions preclude the existence of specialized mechanisms?…”

Challenging the neurobiological link between number sense and symbolic numerical abilities

“…To date, four studies have directly investigated the issue of congruency during the nonsymbolic number comparison task with neuroimaging: two studies with adults, one with adolescents, and one with children . All four studies did show a number of regions that exhibited an effect of congruency, where incongruent trials of the same numerical ratio elicited a greater response than congruent trials, indicating the engagement of mechanisms used to resolve conflicting visual congruency.…”