A new study by researchers of the Human Brain Project suggests that an alteration of the normal coordination between subcortical and cortical regions of the brain can be an important mechanism explaining neurological dysfunction after suffering a stroke. The researchers, who have published their results in Nature Communications, looked into spontaneous patterns of communications as an indicator of stroke-related damage and disruption of function.   

    
“Stroke commonly damages subcortical white matter, rather than cortical gray matter. Much of the damage actually comes from the disruption of long-range connections between cortical regions that travel through the subcortex, rather than a direct injury to cortical regions,” explain Chiara Favaretto from the University of Padova (Italy) and Michele Allegra from Aix-Marseille University (France), lead authors of the study. Using functional magnetic resonance imaging (MRI) during resting state, the researchers compared whole-brain functional and anatomical connectivity patterns between healthy subjects and stroke patients. They showed that the dynamic functional states involve both the cortex and the subcortex, and that shifts between states are accompanied by rapid synchronized changes in both cortical and subcortical regions. The patterns in the brain of the stroke patients were, however, severely altered.   

The anomalous dynamics occurring in stroke patients can be partially predicted on the basis of lesion location and anatomical disconnection patterns, which chiefly involve subcortical regions, suggesting that disruption of normal cortical-subcortical communication can play a significant role in causing anomalous spontaneous dynamics in stroke patients. “While there is overwhelming evidence that spontaneous patterns are correlated with cognitive performance and dysfunction, the mechanisms are still poorly understood,” says Favaretto.

While the researchers relied on fMRI data analysis for the study, they are looking forward to using whole-brain virtual modelling for personalized neurostimulation therapies. “A key goal of our research is to achieve a computational model able to predict, at an individual level for each stroke patient, functional disruption and functional recovery based on anatomical information about the lesions,” they explain. “Such a model would help to predict the clinical trajectory of each patient, assisting clinical decisions. Furthermore, it could inform the development of stimulation-based therapies aimed at recovering normal functioning in stroke patients by re-establishing normal spontaneous brain activity.”

Reference: Favaretto, C., Allegra, M., Deco, G., Metcalf, N.V., Griffis, J.C., Shulman, G.L., Brovelli, A. & Corbetta, M.Subcortical-cortical dynamical states of the human brain and their breakdown in stroke. Nature Communications 13, 5069 (2022). doi.org/10.1038/s41467-022-32304-1