Transcranial Direct Current Stimulation of the Left Temporal Lobe Modulates Insight

Creativity is the ability to come up with new and original solutions to problems. It is characterized along a dipole spectrum, with the opposing ends defined as convergent and divergent thinking. Previous studies have provided evidence that various cognitive functions and insight into non-verbal problems can be enhanced using non-invasive brain stimulation. The aim of this pilot study was to investigate whether convergent and divergent thinking, as well as insight, can be modulated by transcranial direct current stimulation (tDCS) over the anterior temporal lobe (ATL). Bilateral tDCS (1.5 mA, 20 minutes) was used to modulate activity of the right (AR tDCS) and the left (AL tDCS) ATL. Twenty-one participants performed a divergent thinking test (DTT) during tDCS, while a Remote Associates Task (RAT) was administered before and after tDCS to assess convergent thinking. A control experiment, using a Simple Reaction Time (SRT) Task, was conducted in 10 subjects before and after ATL tDCS in order to investigate whether its effects reflect attention or motor effects on the dominant hand. Results from this preliminary study showed that AL tDCS reduced RAT reaction times (RTs) by 20%. Both AL and AR tDCS did not change RAT accuracy, or the DTT total or sub-item scores. No differences were found in the SRT task after either AL or AR tDCS. These findings suggest that left but not right ATL is involved in convergent thinking. Conversely, both left and right temporal cortex tDCS-induced excitability changes failed to modulate divergent thinking. Limitations are discussed.