Frontal networks associated with command following after hemorrhagic stroke

Area of Science:

• Neuroscience
• Neurology
• Neuroimaging

Background:

• Command following is a key clinical indicator of consciousness.
• The specific brain circuits underlying command following remain poorly understood.

Purpose of the Study:

• To identify brain networks differentiating command-following from non-command-following patients post-hemorrhagic stroke.
• To investigate the role of the default mode network (DMN) and task-positive network in command processing.

Main Methods:

• Structural MRI, resting-state functional MRI (fMRI), and electroencephalography (EEG) were used in 25 patients with acute hemorrhage.
• Analysis focused on functional connectivity within standard resting-state networks, particularly the DMN and task-positive network.
• EEG coherence was examined in regions of interest identified by fMRI.

Main Results:

• Significant functional connectivity differences were observed in 6 of 16 resting-state networks, notably in frontal regions (premotor cortex, anterior cingulate, supplementary motor area).
• Unresponsive patients showed disrupted DMN connectivity, including loss of anticorrelation with the task-positive network and new connections between these networks.
• Decreased EEG coherence was found between electrodes corresponding to the right executive and visual networks.

Conclusions:

• Multiple frontal brain networks are essential for command following.
• Disruption of DMN and task-positive network interplay, potentially involving loss of inhibitory control, is associated with unresponsiveness.
• Frontal network integrity is a critical target for understanding and potentially improving responsiveness in intensive care unit patients.