In a study published in the New England Journal of Medicine (DOI: 10.1056/NEJMoa2400645), scientists analyzed the cases of 241 people with severe brain injuries who were unresponsive to simple commands. These people were examined using functional magnetic resonance imaging (fMRI), electroencephalography (EEG), or both.
During the tests, the researchers asked questions like, “Imagine opening and closing your hand,” and after 15 to 30 seconds, “Stop imagining opening and closing your hand.” These and similar questions were repeated for several minutes. Although they were unable to respond in any way, fMRI and EEG scans showed brain activity in 60 (25 percent) of the participants when they were asked to follow instructions. According to the study authors, these people understand language and instructions and are able to pay attention even though they do not interact in any visual way.
These findings mean that a significant number of people with brain injuries who appear to be unresponsive to stimuli can hear and perceive what is happening around them. This finding has potential implications for how care is managed for people classified as comatose, in a vegetative state, or in a minimally conscious state.
The rest of the article is below the video.
cognitive motor disintegration
The ability to respond mentally but not physically is known as cognitive motor dissociation (CMD). In this case, cognitive abilities are not related to motor skills. Scientists have only been studying CMD for a few years. In a 2019 publication, 15 percent of 104 people tested were found to have CMD.
“Some patients with severe brain damage seem unable to process their outside world. But when they are evaluated with advanced techniques like functional magnetic resonance imaging and electroencephalography, we can detect activity in their brains that suggests otherwise,” said the study’s lead author, Dr. Yelena Bodin of the Center for Neurotechnology and Neurohealing at Massachusetts General Hospital.
This study included data from participants from six different centers in Europe and the USA, collected over a period of approximately 15 years. Each center had carefully developed and tested its methods for detecting cognitive-motor dissociation to minimize the possibility of false positives. Some centers recruited participants from the intensive care unit just days after they had suffered a severe brain injury, often as a result of a traffic accident, stroke, or heart attack. Others included patients who had suffered an injury months or years before the fMRI and EEG studies were performed.
In addition to the 241 participants who did not respond to any commands, the researchers analyzed 112 participants who responded to simple instructions. This group was expected to perform well on both fMRI and EEG tests, but in 62 percent, the researchers detected no brain activity. The researchers suggest that this may indicate that the methods used are still not catching all cases. Interestingly, CMD was detected more frequently in patients tested with both fMRI and EEG, suggesting that a combination of tests should be used to detect it.
“To continue our progress in this area, we need to validate our tools and develop methods to systematically and practically assess non-responding patients to make testing more accessible,” Boden said.
Caring for people with CMD
Just knowing that someone is conscious, even if they don’t seem to be at first glance, can make a huge difference in their care. First, it changes the way doctors, scientists, and families interact with such a person. They pay more attention to subtle behavioral signs, talk to the patient, tell stories, or play music. Failure to detect cognitive-motor dissociation can have serious consequences, including premature removal from life support equipment or failure to perform rehabilitation.
“We now have an ethical obligation to engage these patients to try to help them connect with the world,” said the study’s senior author, Dr. Nicholas Schiff, of Weill Cornell Medical College in New York.
One limitation of the study was the lack of standardized testing. Each research facility tested patients in its own way. Additionally, many people were enrolled in the trials because family members heard about them and contacted the researchers. This recruitment approach limits the researchers’ ability to determine the global prevalence of cognitive-motor dissociation.
Other studies have examined brain-computer interfaces (BCIs) as a potential intervention for many types of patients who are unable to communicate. BCIs are devices implanted in the brain that record, decode, and translate brain activity into text or cursor movement on a computer screen.
Source: Mass General Brigham, Nature, Science Alert, Photo: K Whiteford/ Public Domain Pictures/ CC0
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