Dissociation of subtraction and multiplication in the right parietal cortex: Evidence from intraoperative cortical electrostimulation

Abstract

a b s t r a c tPrevious research has consistently shown that the left parietal cortex is critical for numerical processing, but the role of the right parietal lobe has been much less clear. This study used the intraoperative cortical electrical stimulation approach to investigate neural dissociation in the right parietal cortex for subtraction and multiplication. Results showed that multiplication (as well as picture naming) was not affected by the cortical electrical stimulation on all the targeted sites of the right parietal cortex as well as those of the right temporal cortex. In contrast, stimulation at three right parietal sites (two sites in the right inferior parietal lobule and one in the right angular gyrus) impaired performance on simple subtraction problems. This study provided the first evidence from an intraoperative cortical electrical stimulation study to show the dissociation of arithmetic operations in the right parietal cortex. This dissociation between subtraction and multiplication suggests that the right parietal cortex plays a more significant role in quantity processing (subtraction) than in verbal processing (multiplication) in numerical processing.

Right parietal cortex and calculation processing: intraoperative functional mapping of multiplication and addition in patients affected by a brain tumor

“…Two reports have been published on this specific issue. 20,25 In 1 case 25 the authors reported their experience with a patient affected by a right temporal glioma. However, multiplication was not impaired when the right parietal cortex was stimulated.…”

“…With regard to electrostimulation mapping of calculation, some experiences have been reported on left parietal lobe mapping, 7,[13][14][15]21,23 while data on right parietal mapping are anecdotal and discordant. 20,25 This difference may be due to the much greater attention given to language mapping so far; however, impairment of mathematical skills can be the cause of serious personal and social difficulties. For this reason, the ability to perform calculation tasks ought to be regarded as a fundamental function.…”

Balancing the 2 Hemispheres in Simple Calculation: Evidence From Direct Cortical Electrostimulation

“…Previous studies on simple math with DCE had concerned almost exclusively the left parietal cortex (Whalen et al, 1997;Duffau et al, 2002;Kurimoto et al, 2006;Roux et al, 2009;Pu et al, 2011;Yu et al, 2011), contrasting with only two reports (Yu et al, 2011;Della Puppa et al, 2014), whereby positive sites were found in the right parietal area. In all these studies the classification of errors was missing, and no comparison was ever made between the two hemispheres.…”

Causal role of the posterior parietal cortex for two-digit mental subtraction and addition: A repetitive TMS study

“…With the same goal, recent studies conducted with direct cortical electrostimulation (DCE) found a role of specific RH areas in simple addition and multiplication (Della Puppa et al, 2013;Della Puppa et al, 2015a;Della Puppa et al, 2015b;Duffau et al, 2002;Roux et al, 2009;Semenza et al, 2016) and subtractions (Yu et al, 2011). Finally, by means of a technique similar to rTMS and DCE (i.e., transcranial direct current stimulation, tDCS) and focusing on the acquisition of mathematical knowledge, Grabner and colleagues (2015) demonstrated that the left posterior parietal cortex is causally involved in arithmetic learning of two-digit operations.…”