ORIGINAL PAPER
Introduction: Reconsidering Disorders of Consciousness
in Light of Neuroscientific Evidence
Ralf J. Jox & Katja Kuehlmeyer
Received: 22 August 2011 /Accepted: 7 September 2011
# The Author(s) 2011. This article is published with open access at Springerlink.com
Abstract Disorders of consciousness pose a sub-
stantial ethical challenge to clinical decision mak-
ing, especially regarding the use of life-sustaining
medical treatment. For these decisions it is para-
mount to know whether the patient is aware or not.
Recent brain research has been striving to assess
awareness by using mainly functional magnetic
resonance imaging. We review the neuroscientific
evidence and summarize the potential and problems
of the different approaches to prove awareness.
Finally, we formulate the crucial ethical questions
and outline the different articles in this special issue
on disorders of consciousness.
Keywords Disorders of consciousness . Vegetative
state .Minimally conscious state . End-of-life
decisions . Functional magnetic resonance imaging
Progress in medicine allows more and more people in
critical conditions to be kept alive. Some of these
patients, however, do not fully regain consciousness
due to substantial brain damage. If life-sustaining
treatment is applied, they may remain in chronic
disorders of consciousness for decades, living in a
vegetative state (VS) or a minimally conscious state
(MCS). The VS is characterized by preserved sleep-
wake-cycles and spontaneous breathing, which is due
to a largely intact brainstem function, yet there are no
signs of behavioural reactions to stimuli, interaction,
or communication. It is assumed that a patient in the
VS is awake but not aware of himself or his
surroundings [1]. Due to the pejorative connotation
of the term ‘vegetative’ the European Task Force on
Disorders of Consciousness has recently suggested
the term unresponsive wakefulness syndrome (UWS)
[2]. In contrast to the VS, a patient in MCS displays
inconsistent, but reproducible purposeful behaviour,
heralded by subtle signs such as visual pursuit, correct
object use, intelligible verbalisation, or following
simple commands [3]. It is assumed that awareness
is preserved in the MCS, at least at a basic level. Both
disorders of consciousness have to be strictly distin-
guished from the locked-in state (LiS). Patients in a
LiS are usually fully conscious, but cannot express
themselves due to extensive paralysis, yet many are
able to use vertical eye or eyelid movements to
communicate.
The LiS demonstrates that awareness does not
necessarily hinge on the ability to express oneself or
interact with others, be it verbally or through
behaviour. Therefore, the absence of evidence for
awareness is not tantamount to evidence for the
absence of awareness. How can we then determine
whether a person is aware or not? Is it possible to
Neuroethics
DOI 10.1007/s12152-011-9138-0
R. J. Jox (*) : K. Kuehlmeyer
Institute for Ethics, History and Theory of Medicine,
University of Munich,
Lessingstraße 2,
D-80336 München, Germany
e-mail: ralf.jox@med.lmu.de
URL: www.egt.med.uni-muenchen.de

prove the absence or presence of awareness in
patients diagnosed with VS or MCS using neurosci-
entific technology? Many researchers have tried to
answer this question by presenting stimuli to patients
and registering the reaction using either electrophys-
iological or functional brain imaging techniques.
They not only used intensive stimuli such as pain,
but also personally meaningful stimuli such as the
verbal presentation of the patient’s own name. Some
patients showed reactions that were similar to healthy
controls [4, 5]. Selected patients have also been
shown to activate the neural correlates of speech
comprehension in functional magnetic resonance
imaging (fMRI) [6]. Yet, these passive paradigms
only demonstrate that a certain brain response follows
a given stimulus. Whether this response is accompa-
nied by awareness, however, is beyond the reach of
these experiments. It is well conceivable that cortical
networks for pain processing or auditory processing
may function independently of awareness. After all,
we know from our daily life that we are able to
unconsciously perform complex actions like brushing
our teeth or driving a car. Salient stimuli, like being
presented one’s own name, may prompt automatic brain
responses due to facilitated synaptic projections.
Thus, brain researchers moved on to active
paradigms. Here, assuming that they are aware and
understand verbal language, patients are asked to
perform mental tasks (e.g. counting, imagining).
Patients in VS and MCS were instructed to imagine
playing tennis or walking through their homes while
lying in the fMRI scanner [7]. These tasks produce
two distinct and reliable fMRI patterns in healthy
subjects. In a recently published case series, the fMRI
demonstrated the same two activity patterns in five
VS patients in their response to the tasks [8]. The
authors took this as proof that the patients were able
to wilfully modulate their brain activity, alternating
between the tennis and the navigation tasks. The
rather bold conclusion, which stated that these
patients consciously and voluntarily chose to activate
a certain brain network, was heavily criticised [9, 10].
The next step was to try to establish a basic form of
communication with patients. They were asked to use
the two mental activities (playing tennis and naviga-
tion) to signal “yes” or “no” to presented questions
[8]. Indeed, one VS patient was reported to have
responded with the correct brain activity pattern when
asked biographical questions, for example whether
the name of his father was Alexander or Thomas. This
form of communication, however, has only been
demonstrated by one of the 54 patients in the study
[8]. Obviously, it is a rather small subset of VS
patients that shows this remarkable ability to commu-
nicate. Moreover, this approach must promise several
functions in order to prove the presence of conscious-
ness: it requires, for example, an intact auditory
pathway, functioning language networks of the
cortex, and uninjured cortical areas for movement
planning and navigation. Given the fact that all of
these cognitive capacities need extensive areas of the
brain to be intact, it is highly improbable that these
capacities will be preserved in many brain injured
patients. This means, however, that the approach will
yield false negative results regarding the question
whether the patient is aware or not. This might
explain that many MCS patients in the study were
not able to follow the task, even though they were
presumed to be aware according to behavioural
testing [8]. This also raises the question on what
basis patients should be diagnosed: on the traditional
basis of behavioural tests like the Coma Recovery
Scale-Revised, or on the basis of functional imaging
studies using active paradigms?
This is why a new approach to prove awareness is
a purely objective one that does not presuppose any
cognitive capacities: if people undergo an fMRI scan
without a given task, just “lying and thinking of
nothing,” they exhibit activity in two so-called resting
state networks that alternate every few seconds.
Researchers hypothesize that these networks might
signify the awareness of oneself and of one’s
surroundings [11]. It has already been discovered that
the activation of those networks are reduced in
patients with disorders of consciousness [12]. The
problem with this approach is, on the other hand, that
the underlying hypothesis that these networks neces-
sarily herald awareness is still unproven. This touches
on the epistemological problem that a subjective
entity such as awareness cannot be proven purely by
objective measurement—without the person intersub-
jectively revealing himself as a conscious being.
Although many of these neuroscientific results
have not been rigorously confirmed, it has already
been discussed what they mean for the ethical
evaluation of the patient’s condition and how they
should influence the clinical decision concerning
whether to keep patients alive or not [13]. It has even
R.J. Jox, K. Kuehlmeyer