Functional role of frontal alpha oscillations in creativity

Abstract

Creativity, the ability to produce innovative ideas, is a key higher-order cognitive function that is poorly understood. At the level of macroscopic cortical network dynamics, recent electroencephalography (EEG) data suggests that cortical oscillations in the alpha frequency band (8-12 Hz) are correlated with creative thinking. However, whether alpha oscillations play a functional role in creativity has remained unknown. Here we show that creativity is increased by enhancing alpha power using 10 Hz transcranial alternating current stimulation (10 Hz-tACS) of the frontal cortex. In a study of 20 healthy participants with a randomized, balanced cross-over design, we found a significant improvement of 7.4% in the Creativity Index measured by the Torrance Test of Creative Thinking (TTCT), a comprehensive and most frequently used assay of creative potential and strengths. In a second similar study with 20 subjects, 40 Hz-tACS was used instead of 10 Hz-tACS to rule out a general "electrical stimulation" effect. No significant change in the Creativity Index was found for such frontal 40 Hz stimulation. Our results suggest that alpha activity in frontal brain areas is selectively involved in creativity; this enhancement represents the first demonstration of specific neuronal dynamics that drive creativity and can be modulated by non-invasive brain stimulation. Our findings agree with the model that alpha recruitment increases with internal processing demands and is involved in inhibitory top-down control, which is an important requirement for creative ideation.

Keywords: Alpha power; Divergent thinking; Gamma activity; Torrance Test of Creative Thinking (TTCT); Transcranial alternating current stimulation (tACS).

Conflict of interest statement

Conflict of interest

The UNC conflict of interest office has determined that there is no conflict of interest for this study. UNC has filed a non-provisional patent on tACS-related technology with Flavio Frohlich as the lead inventor. No licensing has occurred and none of the authors are financially or otherwise benefitting from this initial filing.

Copyright © 2015 Elsevier Ltd. All rights reserved.

Figures

Fig. 1. Study design, creativity task, and tACS paradigm

(A) Each participant had two experimental sessions during the same day. 10Hz-tACS (verum condition) was applied during one of the two sessions (for the duration of the creativity task) and an active sham condition was applied in the other. Stimulation condition and test forms (A or B) of the Torrance Test of Creative Thinking (TTCT, Torrance, 1998) were applied in a randomized and balanced cross-over design. (B) Sample responses of the TTCT picture completion task performed by two participants with different creativity levels. Participants had to use incomplete predefined forms (green), form a new picture, and make up a title for each drawing as original and unique as possible (e.g. “nutcracker” in sample response). Left: Sample response form participant with Creativity Index of 138 (high creative ideation). Right: Participant with Creativity Index of 98 (low creative ideation). (C) Stimulation electrodes were positioned bilaterally over the frontal cortex (centered on EEG electrode locations F3 and F4) with a common electrode over the apex (Cz). Each electrode pair (F3-Cz, F4-Cz) was controlled by a separate stimulation channel that both applied a synchronized 10 Hz sine-wave stimulation waveform with zero phase offset. This configuration allowed for synchronized stimulation of both frontal lobes. Experiment 2 included a 40 Hz sine-wave stimulation (not shown in figure)

Fig. 2. 10Hz-tACS increases creative thinking

(A) Creativity Index score, a summary measure of creative potential and strengths, for the verum (10Hz-tACS) and sham stimulation condition (mean + s.e.m). Significance of higher Creativity Index for 10Hz-tACS compared to sham was determined by linear mixed model analysis (F1,16 = 5.14, p = 0.036 for factor condition, indicated by star). (B) Individual percentage change in Creativity Index relative to sham (no change to sham denoted as 0 %). Participants were sorted according to their tACS related relative improvement in creative thinking. Black bars illustrate participants with a relative increase (N = 12) and grey bars participants with a relative decrease (N = 7).

Fig. 3. Effects of 10Hz-tACS on individual creativity subscales

10Hz-tACS increased creative thinking across all subscales (mean + s.e.m. percentage change in TTCT subscales relative to sham). Linear mixed model analysis revealed overall significant stimulation condition effect including all subscales (F1,166 = 15.43, p<0.001) but no significant interaction between subscales and stimulation condition (F4,162 = 1.58, p = 0.18).

Fig. 4. 40Hz-tACS does not affect creative thinking

(A) Creativity Index score, for the verum (40Hz-tACS) and sham stimulation condition (mean + s.e.m). No significant difference of the Creativity Index for 40Hz-tACS compared to sham as determined by linear mixed model analysis (F1,17 = 0.01, p = 0.93 for factor condition). (B) Individual percentage change in Creativity Index relative to sham (no change to sham denoted as 0 %). Participants were sorted according to their tACS-related relative improvement in creative thinking. Black bars illustrate participants with a relative increase (N = 8) and grey bars participants with a relative decrease (N = 10). Participants P32 and P36 had no change.