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.
Creativity, the ability to produce novel and useful work, is one of the most extraordinary capabilities of the human mind (Sawyer, 2011). Yet, the neural basis of creativity remains poorly understood (Dietrich & Kanso, 2010). At the level of macroscopic brain dynamics measured with electroencephalography (EEG), oscillatory activity in the alpha frequency band (8–12 Hz) correlates with creative ideation (Fink & Benedek, 2014). In particular, creative idea generation was associated with increased oscillation power in the alpha band in prefrontal and parietal cortical areas (Fink et al., 2007 and Jauk et al., 2012). Also, enhanced alpha power was more pronounced in highly creative people, for more original ideas, and during demanding creative tasks (Fink & Benedek, 2014). In further support of the importance of alpha oscillations, creativity-enhancing, behavioral interventions were associated with increased alpha recruitment, especially at frontal brain sites (Fink et al., 2006 and Fink et al., 2011). Despite this convergence of evidence of an association between alpha oscillations and creativity, it has remained unknown whether alpha activity is causally involved in creative ideation since previous studies of cognitive enhancement by brain stimulation have focused on targeting specific brain areas and not network dynamics (Luft, Pereda, Banissy, & Bhattacharya, 2014). Transcranial alternating current stimulation (tACS) is a non-invasive brain stimulation modality that applies weak, oscillating electric currents to the scalp to enhance endogenous cortical oscillations at the applied frequency (Herrmann et al., 2013, Schmidt et al., 2014 and Vossen et al., 2014). TACS has recently provided causal evidence for oscillations in specific frequency bands mediating memory consolidation, motor control, sensory processing, and fluid intelligence (Fröhlich, 2014, Herrmann et al., 2013 and Santarnecchi et al., 2013). Alpha oscillations are likely generated and modulated by thalamo-cortical and intra-cortical circuits (Bollimunta et al., 2011 and Hindriks and van Putten, 2013) and are therefore susceptible to cortical brain stimulation. Indeed, recent advances in simultaneous EEG and tACS have demonstrated that stimulation in the alpha frequency band selectively enhanced alpha oscillations during and briefly after stimulation (Helfrich et al., 2014b and Zaehle et al., 2010). We here used bifrontal tACS in the alpha frequency range (10 Hz-tACS) to determine if alpha oscillations play a functional role in creativity. In a second experiment we applied 40 Hz-tACS to rule out a general “electrical stimulation” effect.
