New tool peeks into brain to measure consciousness (Update)

August 14, 2013 by Lauran Neergaard

When people have a brain injury so severe that they can't squeeze a loved one's hand or otherwise respond, there are few good ways to tell if they have any lingering awareness or are in a vegetative state. Now researchers have created a tool to peek inside the brain and measure varying levels of consciousness.

The work reported Wednesday is highly experimental, not ready for bedside use yet—and if it pans out, a big question is how to use it without raising false hope. No one knows what level of consciousness at a certain point after injury really predicts recovery.

But it offers the hope that one day doctors might track consciousness nearly as easily as they check blood pressure.

"Consciousness can grow and shrink," said Dr. Marcello Massimini, a neurophysiologist at Italy's University of Milan who led the research to quantify just how much that is happening under different circumstances.

It seems obvious—consciousness fades during deep sleep, and doctors can slip us under with anesthesia. Yet scientists don't have a good way to measure consciousness, especially when the very ill appear to be unconscious. It's important to try to distinguish if patients are at least minimally conscious, and not in a vegetative state, because the sooner there's some sign of awareness, the better the chance of recovery.

Today, doctors check if those patients can do things like blink or move a limb on command, or react to touch or pain. If not, scans of the brain's electrical activity may offer clues. Scientists even have put seemingly unconscious patients inside MRI scanners and told them to imagine throwing a ball. How the brain reacts can indicate if they're aware and just can't show it, what's called locked-in syndrome. But all these tests have drawbacks.

This movie illustrates the basic steps required to calculate PCI and the main results obtained in sleep, anesthesia and brain-injured patients. Measuring PCI involves perturbing the brain with transcranial magnetic stimulation and recording its immediate response by means of electroencephalography. Zipping the brain’s response to a magnetic perturbation to calculate its information content allows discriminating between conscious and unconscious subjects. Credit: Adenauer G. Casali

The new work, reported in the journal Science Translational Medicine, aims for an easier, more objective measure. It's based on the theory that consciousness depends on the complexity of activity in the brain, how well different regions connect and process information. For example, when you're deeply asleep, the neighbor's car alarm may not wake you but your brain still processes that you heard it. When you're wide awake, it also processes how annoying the alarm is and how often it goes off.

Massimini's team combined two well-known medical devices. First, a coil delivers a powerful pulse of magnetism that travels through the skull to stimulate the brain, essentially knocking on it to say "wake up." Then an EEG, which measures brain waves through electrodes attached to the scalp, records the patterns of activity as neurons fire in response.

The final trick: The researchers created a formula to compare the complexity of those resulting brain patterns by "zipping" them, like digital files are compressed so they can be emailed. They called the resulting numerical measurement the PCI, or pertubational complexity index.

The team compared tests from 32 healthy people who were awake, asleep, dreaming or anesthetized, and 20 people with a variety of serious brain injuries. The two patients with locked-in syndrome clearly were aware, scoring nearly as high as awake and healthy people, they reported. The patients diagnosed as being in a vegetative state had scores as low as people rendered unconscious by the most powerful anesthesia. The minimally conscious were somewhere in-between.

The strategy could miss consciousness, so it wouldn't give doctors enough information for end-of-life decisions, researchers caution.

But it's a pioneering study that offers highly promising leads, said Dr. Nicholas Schiff, a professor of neurology and neuroscience at Weill Cornell Medical College in New York, who wasn't part of the project.

If it's ultimately proven to work, the bigger impact could be in helping doctors study whether patients improve when given different treatments, added Dr. Lori Shutter, a brain intensive care specialist at the University of Pittsburgh, who also wasn't involved with Wednesday's work.

But she cautioned that just finding a glimmer of consciousness could mislead families hoping for a miracle long after the possibility for improvement is over.

"This may provide a lot of insight," Shutter said. "The downside is once you prove there's any consciousness, how will a family react?"

Explore further: Electrical signatures of consciousness in the dying brain

More information: Paper stm.sciencemag.org/content/5/198/198ra105

Related Stories

Electrical signatures of consciousness in the dying brain

August 12, 2013
The near-death experience reported by cardiac arrest survivors worldwide may be grounded in science, according to research at the University of Michigan Health System.

A combined method for detecting consciousness

January 9, 2012
The combination of transcranial magnetic stimulation and electroencephalography constitutes a new method allowing the traces of conscious activity to be revealed in brain injured patients.

Toward a better understanding of human consciousness

September 17, 2012
(Medical Xpress)—What consciousness is, and why and how it exists, are some of the oldest questions in philosophy. They are also central to one of the fastest-growing areas of neuroscience.

Research discovers how brain activity changes when anesthesia induces unconsciousness

November 5, 2012
Investigators at Massachusetts General Hospital (MGH) and Massachusetts Institute of Technology (MIT) have identified for the first time a pattern of brain activity that appears to signal exactly when patients lose consciousness ...

Research shows brain hub activity different in coma patients

November 27, 2012
(Medical Xpress)—A team of French and British researchers has found that brain region activity for coma patients is markedly different than for healthy people. In their paper published in the Proceedings of the National ...

Can new diagnostic approaches help assess brain function in unconscious, brain-injured patients?

May 9, 2012
Disorders of consciousness such as coma or a vegetative state caused by severe brain injury are poorly understood and their diagnosis has relied mainly on patient responses and measures of brain activity. However, new functional ...

Recommended for you

When the eyes move, the eardrums move, too

January 23, 2018
Simply moving the eyes triggers the eardrums to move too, says a new study by Duke University neuroscientists.

Cognitive training helps regain a younger-working brain

January 23, 2018
Relentless cognitive decline as we age is worrisome, and it is widely thought to be an unavoidable negative aspect of normal aging. Researchers at the Center for BrainHealth at The University of Texas at Dallas, however, ...

Lifting the veil on 'valence,' brain study reveals roots of desire, dislike

January 23, 2018
The amygdala is a tiny hub of emotions where in 2016 a team led by MIT neuroscientist Kay Tye found specific populations of neurons that assign good or bad feelings, or "valence," to experience. Learning to associate pleasure ...

Your brain responses to music reveal if you're a musician or not

January 23, 2018
How your brain responds to music listening can reveal whether you have received musical training, according to new Nordic research conducted in Finland (University of Jyväskylä and AMI Center) and Denmark (Aarhus University).

New neuron-like cells allow investigation into synthesis of vital cellular components

January 22, 2018
Neuron-like cells created from a readily available cell line have allowed researchers to investigate how the human brain makes a metabolic building block essential for the survival of all living organisms. A team led by researchers ...

Finding unravels nature of cognitive inflexibility in fragile X syndrome

January 22, 2018
Mice with the genetic defect that causes fragile X syndrome (FXS) learn and remember normally, but show an inability to learn new information that contradicts what they initially learned, shows a new study by a team of neuroscientists. ...

0 comments

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.