Parietal Representation of Symbolic and Nonsymbolic Magnitude

Abstract

The close behavioral parallels between the processing of quantitative information conveyed by symbolic and nonsymbolic stimuli led to the hypothesis that there exists a common cerebral representation of quantity (Dehaene, Dehaene-Lambertz, & Cohen, 1998). The neural basis underlying the encoding of number magnitude has been localized to regions in and around the intraparietal sulcus (IPS) by brain-imaging studies. However, it has never been demonstrated that these same regions are also involved in the quantitative processing of nonsymbolic stimuli. Using functional brain imaging, we explicitly tested the hypothesis of a common substrate. Angles, lines, and two-digit numbers were presented pairwise, one to the left and one to the right of the fixation point. In the three comparison tasks, participants (n = 18) pressed the key on the side of the largest quantity. In the three control tasks, they indicated the side on which dimming occurred. A conjunction analysis between the three subtractions (comparison task-control task) revealed a site in left IPS that is specifically responsive when two stimuli have to be compared quantitatively, irrespective of stimulus format. The results confirm the hypothesis that quantity is represented by a common mechanism for both symbolic and nonsymbolic stimuli in IPS. In addition, the interaction between task and type of stimulus identified a region anterior to the conjunction site, not specific for quantitative processing, but reflecting general processes loaded by number processing.

The integration between nonsymbolic and symbolic numbers: Evidence from an EEG study

“…In our study, we selected our ROIs based on these studies (Hyde & Spelke, 2009; Libertus et al., 2007) and found the symbolic integration effect in these ROIs. Given that these posterior sites are spatially close to parietal cortex and the fact that parietal cortex, especially the IPS, has been implicated in numerical processing in other studies (Ansari et al., 2005; Fias et al., 2003; Piazza et al., 2004), it is tempting to link our findings to the function of parietal cortex. Yet, the spatial resolution of the EEG/ERP method constrains the power to make such inferences.…”

“…Other studies using different paradigms confirmed this finding (Hsu & Szücs, 2012; Hyde & Spelke, 2009; Rubinsten, Dana, Lavro, & Berger, 2013). In fMRI studies, the IPS was repeatedly found to be activated in nonsymbolic and symbolic number comparison tasks (Ansari, Garcia, Lucas, Hamon, & Dhital, 2005; Fias, Lammertyn, Reynvoet, Dupont, & Orban, 2003). …”

Are numbers special? An overview of chronometric, neuroimaging, developmental and comparative studies of magnitude representation

“…He found that reaction times tend to rise when the discrimination becomes finer (see Welford, 1960). Since then, the distance effect has been shown many times using pairs of lines (e.g., Johnson, 1939;Fias et al, 2003). However, there are numerous examples of other stimuli that show a distance and/or size effect (Table 1).…”

“…For example, Fias et al (2003) obtained a size effect when subjects compared pairs of angles or pairs of lines. When grouping reaction times (RTs) on the basis of the size of the smallest angle (or line) in the pair, participants responded significantly slower with increasing size (or length).…”

“…Human processing of numbers has intrigued researchers from various disciplines such as anthropology (Urton and Brezine, 2005), linguistics (Gordon, 2004;Pica et al, 2004;Wiese, 2003), psychology (Gallistel and Gelman, 1992;Gelman and Butterworth, 2005;Moyer and Landauer, 1967), and cognitive neuroscience (Brannon, 2006;Dehaene et al, 2003;Fias et al, 2003;Nieder, 2005). Previous reviews focused on the question whether the same representation exists for different notations of numbers (i.e., the issue of abstract numerical representation; Brannon, 2006;Dehaene et al, 1998).…”