Summary: A new MRI study reveals previously unseen subcortical brain pathways crucial for sustaining wakefulness and consciousness, shedding light on neurological disorders and offering potential treatment avenues.

Key Takeaways:

  1. The discovery of “default ascending arousal network” sheds light on brain’s role in maintaining wakefulness during rest.
  2. Functional MRI analysis uncovers connections between subcortical arousal network and cortical regions linked to self-awareness.
  3. Potential clinical applications include better tools for detecting and promoting recovery of consciousness in severe brain injury patients, and trials targeting network activation in coma patients for consciousness restoration.


Consciousness relies on wakefulness and awareness. While cortical networks supporting awareness have been extensively studied, the subcortical networks responsible for wakefulness remain poorly understood due to their small size and complexity. In a recent MRI study, researchers mapped a subcortical brain network integrating arousal and awareness, shedding light on this critical aspect of human consciousness.

New Brain Pathways Unveiled

In a study published in Science Translational Medicine titled “Multimodal MRI reveals brainstem connections sustaining wakefulness in human consciousness,” researchers from Massachusetts General Hospital and Boston Children’s Hospital crafted a connectivity map of a brain network deemed crucial to human consciousness. Utilizing high-resolution scans, they identified previously unseen pathways connecting key brain regions at submillimeter spatial resolution.

Together, these pathways form a “default ascending arousal network” that sustains wakefulness in the resting, conscious human brain. The concept of a “default” network is based on the idea that specific networks within the brain are most functionally active when the brain is in a resting state of consciousness. In contrast, other networks are more active when the brain is performing goal-directed tasks.

To explore the functional aspects of this default brain network, the researchers examined 7 Tesla resting-state functional MRI data from the Human Connectome Project. Their analysis unveiled functional connections between the subcortical default ascending arousal network and the cortical default mode network, contributing to self-awareness in the resting, conscious brain.

Mapping Vital Brain Network for Consciousness

These complementary structural and functional connectivity maps establish a neuroanatomic foundation for integrating arousal and awareness in human consciousness. The researchers made the MRI data, brain mapping techniques, and a new Harvard Ascending Arousal Network Atlas available to aid future endeavors in mapping the connectivity of human consciousness.

“Our goal was to map a human brain network that is critical to consciousness and to provide clinicians with better tools to detect, predict, and promote recovery of consciousness in patients with severe brain injuries,” says lead-author Brian Edlow, MD, co-director of Mass General Neuroscience, associate director of the Center for Neurotechnology and Neurorecovery (CNTR) at Mass General, and associate professor of Neurology at Harvard Medical School.

Edlow explains, “Our connectivity results suggest that stimulation of the ventral tegmental area’s dopaminergic pathways has the potential to help patients recover from coma because this hub node is connected to many regions of the brain that are critical to consciousness.”

Unlocking Mysteries of Consciousness

Senior author Hannah Kinney, MD, Professor Emerita at Boston Children’s Hospital and Harvard Medical School, proposes that the identified human brain connections could serve as a roadmap for understanding a spectrum of neurological disorders associated with altered consciousness, spanning from coma to seizures to sudden infant death syndrome, or SIDS.

Furthermore, the authors are currently conducting clinical trials to activate the default ascending arousal network in coma patients with traumatic brain injuries, with the objective of reestablishing the network and reinstating consciousness.