Neural dynamics of semantic control underlying generative storytelling
Storytelling has been pivotal for the transmission of knowledge and cultural norms across human history. A crucial process underlying the generation of narratives is the exertion of cognitive control on the semantic representations stored in memory, a phenomenon referred as semantic control. Despite the extensive literature investigating the neural mechanisms of semantic control in generative language tasks, little effort has been done towards storytelling under naturalistic conditions. Here, we probed human participants to generate stories in response to a set of instructions which triggered a narrative that was either appropriate (ordinary), novel (random), or balanced (creative), while recording functional magnetic resonance imaging (fMRI) signal. By leveraging deep language models, we demonstrated how participants ideally balanced the level of semantic control during story generation. At the neural level, creative stories were differentiated by a multivariate pattern of neural activity in frontal cortices compared to ordinary ones and in fronto-temporo-parietal cortices with respect to randomly generated stories. Crucially, similar brain regions were also encoding the features that distinguished the stories behaviourally. Moreover, we decomposed the neural dynamics into connectome harmonic modes and found specific spatial frequency patterns underlying the modulation of semantic control during story generation. Finally, we found different functional coupling within and between the default mode, salience and control networks when contrasting creative stories with their controls. Together, our findings highlight the neural mechanisms underlying the regulation of semantic exploration during narrative ideation and contribute to a deeper understanding of the neural dynamics underpinning the role of semantic control in generative storytelling.