The Effect of Changing the Balance Between Right and Left Dorsolateral Prefrontal Cortex on Different Creativity Tasks: A Transcranial Random Noise Stimulation Study

Abstract

Transcranial random noise stimulation (tRNS) increases performance in some perceptual tasks. However, little is known about its effect on creativity. Although dorsolateral prefrontal cortex (DLPFC) has been postulated as an important cortical area related to creativity, the relative role of left and right DLPFC is still unclear. We aimed to compare the effect of anodal left/cathodal right (L + R−) and cathodal left/anodal right (L − R+) tRNS over the DLPFC. Eighty-four participants were randomly assigned to L + R−, L−R+ or sham group. Current was set at 2 mA (100-500 Hz) with a 1 mA direct current offset (20 min). Creativity was assessed before and during tRNS with the Remotes Associates Test (RAT), Unusual Uses (UU) and Picture Completion (PC) from Torrance Test of Creative Thinking, nine-dot problem and matchstick arithmetic problems. Bootstrapped analysis of covariance (under-stimulation scores controlling for baseline) showed that L + R− and L − R+ groups had higher scores than sham in UU whereas only L + R− improved in RAT compared to sham. The L − R+ group performed significantly better than L + R− and sham groups in PC, nine-dot problem and matchstick arithmetic problems. L + R− DLPFC may help verbal creative thinking whereas the L − R + seems to produce a "releasing effect" through insight problem solving and originality.

Comparing transcranial direct current stimulation and transcranial random noise stimulation over left dorsolateral prefrontal cortex and left inferior frontal gyrus: Effects on divergent and convergent thinking

“…The results showed that fluency and originality dimensions of visual DT benefited from tRNS stimulation compared to sham, whereas contrary to expected, tDCS did not show any significant effect on DT. The positive effect of tRNS over the left DLPFC on the fluency dimension of DT is to some extent consistent with previous literature ( Lustenberger et al, 2015 ; Zmigrod et al, 2015 ; Grabner et al, 2018 ; Peña et al, 2019 , 2021 ). However, the significant effect of tRNS on originality was not expected since some of the previous studies have shown even a reduction in novelty of responses after the excitatory stimulation of the left IFG, which was what the tRNS group received ( Ivancovsky et al, 2019 ; Kenett et al, 2021 ).…”

“…Regarding CT, our results were only marginally significant and it may mean a lack of statistical power, so we cannot conclude that tDCS neither tRNS over left DLPFC and IFG do significantly affect RAT scores. However, the trend toward a better performance after both tDCS and tRNS would be consistent with many studies that have shown that the stimulation of the left DLPFC is associated with an improvement in RAT using both tDCS (Cerruti and Schlaug, 2009;Zmigrod et al, 2015) and tRNS (Peña et al, 2019(Peña et al, , 2021. A possible explanation for this result is that the stimulation of left DLPFC would enhance RAT performance by strengthening the maintenance of focused attention, top-down support for relevant information, manipulation of information in working memory and inhibition of task-irrelevant information (Fischer and Hommel, 2012;Zhang et al, 2020).…”

“…Results from transcranial stimulation studies mainly indicate that anodal tDCS over left DLPFC may increase DT ( Colombo et al, 2015 ; Zmigrod et al, 2015 ; Peña et al, 2021 ) and CT ( Cerruti and Schlaug, 2009 ; Metuki et al, 2012 ; Zmigrod et al, 2015 ; Peña et al, 2021 , 2019 ). However, in separate studies, cathodal tDCS over the left IFG also found an increase in DT ( Mayseless and Shamay-Tsoory, 2015 ; Kleinmintz et al, 2018 ; Hertenstein et al, 2019 ; Ivancovsky et al, 2019 ; Khalil et al, 2020 ; Chrysikou et al, 2021 ; Kenett et al, 2021 ).…”

Enhancing Creativity With Combined Transcranial Direct Current and Random Noise Stimulation of the Left Dorsolateral Prefrontal Cortex and Inferior Frontal Gyrus

“…Some authors found a significant improvement in MA problems after cathodal left/anodal right tDCS over the ATL (Chi & Snyder, 2011) and DLPFC (Di Bernardi Luft et al, 2017;Peña et al, 2021), whereas another study did not (Aihara et al, 2017). Regarding the ND problem, cathodal left/anodal right tDCS over the ATL (Chi & Snyder, 2012) as well as cathodal left/anodal right tDCS-tRNS over the DLPFC (Pe ña et al, 2021) have shown significant improvement. In sum, although not completely consistent, the previously mentioned literature mainly suggests that anodal tDCS of left DLPFC may increase both CT (Cerruti & Schlaug, 2009;Metuki et al, 2012;Peña et al, 2019Peña et al, , 2021Zmigrod et al, 2015) and DT (Colombo et al, 2015;Peña et al, 2021;Zmigrod et al, 2015).…”

“…As such, each electrode sends a mix of both tDCS and tRNS, by adding the random noise stimulation (1 mA) over the direct current stimulation at (1 mA) results in tRNS waveforms being positive (1.5-0.5 mA) thus avoiding tRNS changing polarity from positive to negative (+0.5 to −0.5 mA) in the same electrode without a tDCS offset (Figure 1). Using this hybrid type of tES (tDCS-tRNS) over the DLPFC, some authors found that the left anodal-right cathodal group induced higher scores in both fluency and originality scores of verbal DT compared with sham, but not compared with the opposite montage, which also improved verbal DT (Pe ña et al, 2021). Their result regarding visual DT suggested that only left cathodal-right anodal group improved visual originality and fluency compared with sham.…”