In a recent study published in Science Translational Medicine, researchers from Massachusetts General Hospital and Boston Children’s Hospital utilized high-resolution structural and functional MRI scans to map a subcortical brain network that is believed to be essential for human consciousness. This network, referred to as the “default ascending arousal network,” is responsible for sustaining wakefulness in the resting, conscious human brain. The study revealed previously unseen pathways connecting the brainstem, thalamus, hypothalamus, basal forebrain, and cerebral cortex, highlighting the intricate connections that support arousal and awareness in human consciousness.
The concept of a “default” network within the brain suggests that specific networks are most active during a resting state of consciousness, while others are more active during goal-directed tasks. The researchers analyzed data from the Human Connectome Project to investigate the functional properties of the subcortical default ascending arousal network and its connections to the cortical default mode network, which contributes to self-awareness in the resting brain. These findings provide a neuroanatomic basis for understanding how arousal and awareness are integrated in human consciousness.
The researchers also released the MRI data, brain mapping methods, and a new Harvard Ascending Arousal Network Atlas to support future efforts in mapping the connectivity of human consciousness. Their goal is to provide clinicians with better tools to detect, predict, and promote recovery of consciousness in patients with severe brain injuries. Lead author Dr. Brian Edlow emphasizes that stimulation of the ventral tegmental area’s dopaminergic pathways could potentially help patients recover from coma, as this hub node is connected to critical regions of the brain that are important for consciousness.
Senior author Dr. Hannah Kinney notes that the human brain connections identified in the study can be used as a roadmap to better understand various neurological disorders associated with altered consciousness, such as coma, seizures, and sudden infant death syndrome (SIDS). The researchers are currently conducting clinical trials to stimulate the default ascending arousal network in patients with coma after traumatic brain injury, with the aim of reactivating the network and restoring consciousness.
Overall, the study highlights the importance of the default ascending arousal network in sustaining wakefulness and integrating arousal and awareness in human consciousness. By mapping the intricate connections within this network, the researchers aim to advance our understanding of consciousness and develop new strategies for treating neurological disorders that impact consciousness. The release of the MRI data and brain mapping methods will support future research efforts to further explore the complexities of human consciousness and improve clinical outcomes for patients with severe brain injuries.
