The cognitive and neural bases of creative thought: A cross-domain systematic review and meta-analysis of transcranial direct current stimulation studies.

Creative thought enables humans to flexibly generate, evaluate and select novel and adaptive ideas across different contexts. Decades of research indicates that it involves two key aspects: retrieval of previously acquired knowledge and manipulation of that knowledge. However, the cognitive processes underpinning these aspects remain underspecified. The broader clinical-cognitive neuroscience literature suggests these functions rely on general-purpose cognitive mechanisms supporting semantic cognition, controlled episodic memory retrieval, and executive mechanisms. Transcranial direct current stimulation (tDCS) is a neuromodulation technique widely used in creativity and cognitive neuroscience research to examine causal brain-behaviour relationships. To identify converging evidence toward a unifying neurocognitive account of creative thought, we reviewed and meta-analysed 145 sham-controlled tDCS studies (involving 8399 healthy participants aged 18-40), drawn from electronic databases and previous reviews, across creativity and relevant cognitive neuroscience literatures. The results revealed that, only left lateral frontal anodal tDCS promotes creativity (p < .01). In parallel, anodal tDCS over the same region also promotes improvement in many other cognitive processes, including more efficient processing of semantic knowledge (p < .05), more accurate episodic memory retrieval (p < .05), better and more efficient manipulation of buffered knowledge (all p < .001), better self-initiated response generation (i.e., energization; p < .05), and more efficient response selection amongst competing options (i.e., task-setting; p < .01). By merging these previously separate literatures, tDCS studies - although heavily biased toward frontal montages - support the notion that creative thought arises from general-purpose cognitive mechanisms including controlled retrieval and temporary storage of semantic and episodic information, as well as executive mechanisms.