Early stimulation of the left posterior parietal cortex promotes representation change in problem solving

Ursula Debarnot,Sophie Schlatter,Aymeric Guillot,Julien Monteil

doi:10.1038/s41598-019-52668-7

Ursula Debarnot, Sophie Schlatter + Show 2 more

Open Access

https://doi.org/10.1038/s41598-019-52668-7

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Abstract

When you suddenly understand how to solve a problem through an original and efficient strategy, you experience the so-called “Eureka” effect. The appearance of insight usually occurs after setting the problem aside for a brief period of time (i.e. incubation), thereby promoting unconscious and novel associations on problem-related representations leading to a new and efficient solving strategy. The left posterior parietal cortex (lPPC) has been showed to support insight in problem solving, when this region is activated during the initial representations of the task. The PPC is further activated during the next incubation period when the mind starts to wander. The aim of this study was to investigate whether stimulating the lPPC, either during the initial training on the problem or the incubation period, might enhance representation change in problem solving. To address this question, participants performed the Number Reduction Task (NRT, convergent problem-solving), while excitatory or sham (placebo) transcranial direct current stimulation (tDCS) was applied over the lPPC. The stimulation was delivered either during the initial problem representation or during the subsequent incubation period. Impressively, almost all participants (94%) with excitatory tDCS during the initial training gained representational change in problem solving, compared to only 39% in the incubation period and 33% in the sham groups. We conclude that the lPPC plays a role during the initial problem representation, which may be considerably strengthened by means of short brain stimulation.

Highlights

When you suddenly understand how to solve a problem through an original and efficient strategy, you experience the so-called “Eureka” effect
The most striking result showed that stimulation over the left posterior parietal cortex (lPPC) during initial training on the Number Reduction Task (NRT) drastically boosted the occurrence of insight solving strategy compared to the other experimental conditions
We found that applying a-transcranial direct current stimulation (tDCS) over the lPCC early on the NRT, but not during incubation, strongly potentiated insight solving strategy

Summary

Introduction

When you suddenly understand how to solve a problem through an original and efficient strategy, you experience the so-called “Eureka” effect. A recent neuroimaging meta-analysis highlighted that working on problem solving followed by an incubation period might be underpinned by an antagonistic, albeit cooperative, interaction between the executive control and default mode networks[9] The former is associated to cognitive processes that require externally directed attention, including working memory and task-set switching, whereas the latter is activated without external engagement on an attentional demanding task[10,11]. The present study aimed to test how and when substantially boosting representational change in problem solving To address this question, we tested whether unilateral a-tDCS over the lPPC during either initial practice on the NRT, or the immediate subsequent incubation period, would substantially potentiate the emergence of insight solving strategy

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