Authors :
Presenting Author: Manel Vila-Vidal, PhD – Universitat Politècnica de Catalunya / BrainFocus
Mariam AlKhawaja, MD – Hospital Clínic; Mar Carreño, MD, PhD – Hospital Clínic; Pedro Roldán, MD, PhD – Hospital Clínic; Jordi Rumià, MD, PhD – Hospital Clínic; Gustavo Deco, PhD – Universitat Pompeu Fabra; Antonio Donaire, MD, PhD – Hospital Clínic; Adrià Tauste, PhD – Universitat Politècnica de Catalunya
Rationale:
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. Invasive electroencephalography (iEEG) provides a unique opportunity to directly measure neural activity at different spatial scales and address this question.
Methods:
We designed a simple face-recognition task performed in patients with drug-resistant epilepsy under intracranial EEG monitoring. Local activity was estimated as the high-gamma activity (64–256 Hz) at every recorded gray-matter region. Global connectivity states were characterized using a sliding approach with the following measures: (1) mean functional connectivity (mFC), based on Pearson correlations between contact pairs, (2) mean phase-locking value (mPLV), which measures the consistency of phase differences between contact pairs at each frequency scale. Based on our observations, we developed a novel analytical framework (named “local-global” framework) to statistically correlate the brain activity in every recorded region with the widespread connectivity fluctuations as proxy to identify concurrent local activations and global brain phenomena that may plausibly reflect a common functional network during cognition (Vila-Vidal et al., 2023, Human Brain Mapping, 44(3), 1173-1192, https://doi.org/10.1002/hbm.26150).
Results:
The application of our analysis to the data from six subjects was able to detect local gamma 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 (mFC and mPLV) consistently showed a significant global decrease around alpha and beta bands 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.
Conclusions:
Our results provide evidence that during the cognitive task, global connectivity exhibits consistent trends that might be a signature of functional brain activity reorganization when a stimulus is processed regardless of the specific recorded areas. In addition, our findings suggest that task-driven connectivity fluctuations are linked to local neural activity.
Funding:
MVV was supported by a fellowship from ”la Caixa” Foundation, Spain (ID 100010434, fellowship code LCF/BQ/DE17/11600022). MVV and ATC were supported by the Bial Foundation grant 106/18. GD and ATC were supported by the project ”Cluster Emergent del Cervell Huma” (CECH, ref. 001-P-001682), within the framework of the European Research Development Fund Operational Program of Catalonia 2014-2020. ATC was supported by the Spanish National Research project (ref. PID2020-119072RA-I00/AEI/10.13039/501100011033) funded by the Spanish Ministry of Science, Innovation, and Universities (MCIU). This research was also supported by a grant from “la Caixa” Foundation (CaixaImpulse Validate, project ref. CI20-00195).