P 53. The functional relevance of the posterior parietal cortex in arithmetic learning and performance

Abstract

Introduction The successful acquisition of mathematical competence is one of the key aims of institutional learning and has meanwhile also moved into the center of neuroscientific investigations. Recent research has revealed a potential key role of the left posterior parietal cortex (PPC), in particular the angular gyrus, in arithmetic learning and problem solving. Specifically, the acquisition and retrieval of arithmetic facts (such as multiplication facts) were found to be associated with activation increases in this brain region. However, it remained unclear, whether the function of the left PPC is causally related to arithmetic learning and problem solving. Moreover, there is first evidence that the application of anodal transcranial direct current stimulation (tDCS) supports the acquisition of new numerical symbols and improves performance in a subtraction task. However, it is unclear whether these findings can be generalized to more demanding arithmetic learning processes. Objectives In the present tDCS study, we addressed two research questions: First, is the activation of the left PPC causally related to the successful acquisition and retrieval of arithmetic facts? Second, can arithmetic learning or performance be enhanced by means of tDCS at the left PPC? Materials and methods The study comprised 80 adult students who participated in two test sessions. In the first test session (learning session) participants underwent a 45 min training of a small set of arithmetic facts (5 multiplication and 5 subtraction problems). One day later, in the second test session (performance session), participants were presented with the trained as well as untrained arithmetic problems for 30 min. The participants were divided into 4 experimental groups as depicted in Fig. 1. In anodal and cathodal conditions, tDCS of 1.5 mA was applied over the left PPC for 30 min during training and problem solving. Results Presently, the data of 53 participants have been collected and analyzed. The preliminary analyses revealed a more pronounced effect of tDCS in the performance compared to the learning session. Specifically, the group who received sham stimulation during learning and anodal stimulation during retrieval revealed the best performance in terms of response latencies and solution rates. In the learning session, anodal stimulation was slightly more beneficial for the learning progress than cathodal stimulation. Conclusions The preliminary data analysis provides first evidence for a causal functional role of the left PPC in the retrieval rather than in the acquisition of arithmetic facts. In addition, results suggest that the retrieval performance can be enhanced by means of brain stimulation, whereas neither anodal nor cathodal tDCS seem to have a strong beneficial effect during the learning of arithmetic facts. Overview of stimulation protocols. The break between learning and performance session was 24 h.