Abstract
A putative “number form area” (NFA) in the ventral occipito-temporal cortex (vOTC) is suggested to preferentially process Arabic numerals. The development of selectivity in the vOTC is thought to be driven in part by an area’s unique set of axonal projections but also by repeated co-activation with distinct functional networks over experience. In adults performing number and arithmetic tasks, areas of the right posterior inferior temporal gyrus (pITG) are selectively coupled to sites in the intraparietal sulcus (IPS), a region involved in magnitude processing. It is unclear when in development selective, task-evoked pITG connectivity emerges. To investigate this, we analyzed fMRI data from 47 typically-developing children (6.2 ± 0.4 years, 23 female), who performed symbol classification (digits, letters, scrambled) and symbolic (digits) and nonsymbolic (dots) comparison tasks in the scanner. Surface-based, beta-series correlation analyses were conducted to measure task-evoked coupling of the right pITG during each condition. We predicted that pITG - IPS coupling would be evident, even in kindergarten, when simply identifying a numeral (i.e. during classification), as well as when actively associating a numeral with its magnitude referent (i.e. during comparison). Across all task conditions, the pITG was strongly coupled to a bilateral frontoparietal network including the IPS. We assessed the predicted selectivity of this coupling by contrasting against control conditions involving letter and dot processing, from each task respectively. At the whole-brain level (p<0.05 corrected), we found no significant clusters for digit versus letter classification. For digit versus dot comparison, we found one cluster in the postcentral sulcus greater for dots. We found no evidence in this whole-brain, group-level analysis, that the pITG demonstrates numeral-selective coupling during either classification or comparison tasks in kindergarten. These results suggest that selective coupling emerges later in schooling, perhaps after children have had more experience using numerals in mathematical contexts.