Revealing Hidden Consciousness in Comatose Brains

Revealing Hidden Consciousness in Comatose Brains

Unconscious, Yet Aware: Unveiling the Hidden Consciousness in Acute Brain Injuries

Brain Injury

Some patients with acute brain injuries may appear to be unconscious, but recent research reveals that they actually possess a hidden consciousness. This phenomenon, known as cognitive motor dissociation (CMD), occurs when patients cannot respond to verbal commands but still possess some level of awareness. Dr. Jan Claassen, study leader and associate professor of neurology at Columbia University Vagelos College of Physicians and Surgeons in New York City, explains that these patients can hear and comprehend instructions but are unable to carry them out due to disrupted brain circuits. These findings, published in the journal Brain, could aid in quickly identifying patients with hidden consciousness, predicting recovery with rehabilitation, and improving patient outcomes.

Understanding the Hidden Consciousness:

CMD affects approximately 15% to 25% of patients with brain injuries caused by head trauma, brain hemorrhage, or cardiac arrest. Detecting subtle brainwaves using electroencephalography (EEG) has been shown to be the strongest predictor of hidden consciousness in unresponsive patients. However, it remained unclear which specific brain pathways were disrupted. To shed light on this phenomenon, researchers conducted a study involving over 100 brain injury patients, utilizing EEG to identify and examine CMD.

The Role of EEG in Identifying CMD:

EEG is a technique that can detect when patients are attempting to respond to a command, even if they are physically unable to comply. By analyzing brainwave patterns, researchers identified CMD in 21 out of 107 patients in the study. Comprehensive structural magnetic resonance imaging (MRI) brain scans were carried out on all patients to further study the nature of the brain injuries.

Identifying Commonalities with Bi-Clustering Analysis:

Using a novel technique called bi-clustering analysis, the researchers uncovered shared patterns of brain injury among the CMD patients. Co-lead author Qi Shen, an associate research scientist in the Claassen lab, highlighted the significance of the study’s findings in understanding CMD. The MRI scans showed that all CMD patients had intact brain structures related to arousal and command comprehension. This confirmed that they were indeed hearing and understanding the instructions but were incapable of executing them due to deficits in the brain regions responsible for integrating motor commands with motor output.

The Road Towards Clinical Application:

While further research is needed before these findings can be applied to clinical practice, the study demonstrates the potential of widely available structural MRI brain imaging in screening for hidden consciousness. This approach may serve as a simpler alternative to the utilization of EEG, which requires specialized training and resources. By utilizing MRI, medical professionals in critical care units can quickly identify patients who require further screening and diagnosis.


The discovery and understanding of hidden consciousness in acute brain injuries offer hope for improved diagnosis, treatment, and rehabilitation of patients. This research opens up new possibilities for identifying patients with CMD, predicting their recovery, and tailoring individualized rehabilitation programs. With further studies and advancements, doctors may be able to provide more accurate prognoses and develop targeted interventions, ultimately enhancing the quality of life for patients affected by CMD.

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