Patients in a minimally conscious state remain capable of dreaming during their sleep

August 16, 2011
The brain of "minimally conscious" severely brain damaged patients shows "sleep-wake" activity as in normal healthy subjects. Changes in frontal "slow wave" activity during sleep (areas in red) are considered to reflect some capacity for neural plasticity or natural healing of the brain. © Coma Science Group, University/CHU of Liege

The question of sleep in patients with seriously altered states of consciousness has rarely been studied. Do ‘vegetative' patients (now also called patients in a state of unresponsive wakefulness) or minimally conscious state patients experience normal sleep? Up until now the distinction between the two patient populations had not been taken into account by electrophysiological studies. Yet if the vegetative state opens no conscious door onto the external world, the state of minimal consciousness for its part assumes a residual consciousness of the environment, certainly fluctuating but real.

It is this difference which has led a group of researchers at the Coma Science Group and the universities of Wisconsin and Milan to compare the of these two types of brain damaged patients. The results of their study are published this week in the journal Brain. They demonstrate once again the necessity of an adapted and specific medical care for each of these states.

The researchers' work rested on a sample of 11 subjects (6 in a state of minimal and 5 in a vegetative state) and made use of high density (256 electrodes) electroencephalography (EEG). The goal was to determine the structure of sleep within the two types of patient. "We used as a marker of arousal the fact that the subject had his/her eyes open and muscle tone, and as a marker of sleep the fact that the patient had closed eyes and muscle inactivity," points out Dr. Steven Laureys, the Director of the Coma Science Group.

The high density EEG revealed that the brain's electrical activity differed very little between sleep and wake states in patients in a . On the other hand the sleep of patients in a minimally had characteristics very close to that of normal sleep in a healthy subject. They showed changes in "slow wave" activity in the front of the brain considered important for learning and neural plasticity (figure). It also appeared that these patients produced NREM (non rapid eye movement) slow wave sleep and REM (rapid eye movement) sleep, which is the support for dream activity.

"Everything thus indicates that they have access to dreaming," emphasises Steven Laureys. "As a result, we can legitimately suppose that they still have a form of consciousness of self in addition to a certain consciousness of the external world."

The study published in Brain brings to light a relationship between the electrophysiology of sleep and the degree of consciousness in severely brain damaged patients. Thus, once validated, the method used could constitute an additional tool to evaluate, in a routine clinical setting, the potential maintenance of a residual consciousness in these patients.

Explore further: New test may help distinguish between vegetative and minimally conscious state

More information:Electrophysiological correlates of behavioural changes in vigilance in vegetative state and minimally conscious state', Brain (2011) 134 (8): 2222-2232. doi: 10.1093/brain/awr152

Related Stories

Recommended for you

Rat brain atlas provides MR images for stereotaxic surgery

October 21, 2016

Boris Odintsov, senior research scientist at the Biomedical Imaging Center at the Beckman Institute for Advanced Science and Technology at the University of Illinois in Urbana-Champaign, and Thomas Brozoski, research professor ...

ALS study reveals role of RNA-binding proteins

October 20, 2016

Although only 10 percent of amyotrophic lateral sclerosis (ALS) cases are hereditary, a significant number of them are caused by mutations that affect proteins that bind RNA, a type of genetic material. University of California ...

Imaging technique maps serotonin activity in living brains

October 20, 2016

Serotonin is a neurotransmitter that's partly responsible for feelings of happiness and for mood regulation in humans. This makes it a common target for antidepressants, which block serotonin from being reabsorbed by neurons ...

Overcoming egocentricity increases self-control

October 19, 2016

Neurobiological models of self-control usually focus on brain mechanisms involved in impulse control and emotion regulation. Recent research at the University of Zurich shows that the mechanism for overcoming egocentricity ...

1 comment

Adjust slider to filter visible comments by rank

Display comments: newest first

not rated yet Aug 16, 2011
Baseline research is needed.
If the researchers have confidence in brain locality of sleep functions, then brain fetal development of neuronal sleep patterns with the associated brain circuit activity is baseline. Monitor fetal sleep functions. fMRI is noninvasive.

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.