Assessing the influence of local neural activity on global connectivity fluctuations: Application to human intracranial EEG during a cognitive task

Cognitive-relevant information is processed by different brain areas that cooperate to eventually produce a response. The relationship between local activity and global brain states during such processes, however, remains for the most part unexplored. To address this question, we designed a simple face-recognition task performed in drug-resistant epileptic patients with intracranial EEG. Based on our observations, we developed a novel analytical framework (named “local-global” framework) to statistically correlate the brain activity in every recorded gray-matter region with the widespread connectivity functions as proxy to assess the level of influence of local neural activations into the brain’s global state during cognition. The application of our analysis to the data from two subjects was able to detect the local activity in task-relevant brain areas including the primary visual and motor cortices. Despite substantial differences in the recorded regions of each subject, the connectivity functions consistently showed a significant global desynchronization occurring a few hundred milliseconds after the stimulus onset. In this context, the local-global framework revealed that the reported desynchronization was better explained by the local activity of brain areas involved in face information processing, providing evidence that the global measures might be a novel signature of functional brain activity reorganization taking place when a stimulus is processed in a task context. ### Competing Interest Statement The authors have declared no competing interest.