Cerebral response to patient's own name in the vegetative and minimally conscious states

Is it about the self or the significance? An fMRI study of self-name recognition

Our own name, due to its high social relevance, is supposed to have a unique status in our information processing. However, demonstrating this phenomenon empirically proves difficult as famous and unknown names, to which self-name is often compared in the studies, may differ from self-name not only in terms of the 'me vs. not-me' distinction, but also as regards their emotional content and frequency of occurrence in everyday life. In this fMRI study, apart from famous and unknown names we used the names of the most important persons in our subjects' lives. When compared to famous or unknown names recognition, self-name recognition was associated with robust activations in widely distributed bilateral network including fronto-temporal, limbic and subcortical structures, however, when compared to significant other's name, the activations were present specifically in the right inferior frontal gyrus. In addition, the significant other's name produced a similar pattern of activations to the one activated by self-name. These results suggest that the differences between own and other's name processing may rather be quantitative than qualitative in nature.

Evaluation of technology-assisted learning setups for undertaking assessment and providing intervention to persons with a diagnosis of vegetative state

OBJECTIVE

To evaluate the viability of technology-assisted learning setups for undertaking assessment and providing intervention to persons in vegetative state.

METHOD

Study I investigated whether three persons with a diagnosis of vegetative state could associate eye blinking or hand closure responses with contingent, positive stimulation, thus increasing their frequencies (showing signs of learning). Study II extended the learning process (introducing a new response and new stimuli) for one of the participants of Study I.

RESULTS

Two of the participants of Study I succeeded in increasing their responses, indicating signs of learning. Study II showed that the participant (one of the two succeeding in Study I) acquired a new response to access new stimuli and could alternate this response with the one acquired in Study I.

CONCLUSION

Learning might represent a basic level of knowledge and consciousness. Detecting signs of learning might help modify a previous diagnosis of vegetative state and support intervention/rehabilitation efforts.

Influence of Names on Career Choices in Medicine

AbstractThree studies showed that medical doctors and lawyers were disproportionately more likely to have surnames that resembled their professions. A fourth study showed that, for doctors, this influence extended to the type of medicine they practiced. Study 1 found that people with the surname "Doctor" were more likely to be doctors than lawyers, whereas those with the surname "Lawyer" were more likely to be lawyers. Studies 2 and 3 broadened this finding by comparing doctors and lawyers whose first or last names began with three-letter combinations representative of their professions, for example, "doc," "law," and likewise found a significant relationship between name and profession. Study 4 found that the initial letters of physicians' last names were significantly related to their subspecialty, for example, Raymonds were more likely to be radiologists than dermatologists. These results provide further evidence names influence medical career choices.

Anterior cingulate activity and the self in disorders of consciousness

OBJECTIVES

The aim of this study was to investigate the relationship between medial cortical activation and the presence of self and consciousness in healthy subjects and patients with vegetative state and minimally conscious state using functional magnetic resonance imaging (fMRI).

EXPERIMENT DESIGN

We first conducted two fMRI experiments in healthy subjects to identify brain regions specifically associated with self-perception through the use of different auditory stimuli that had different grades of self-relatedness. We then applied these regions as functional localizers to examine the relationship between neural activity changes during self-relatedness and consciousness level in the patients with disorders of consciousness (DOC).

PRINCIPAL OBSERVATIONS

We demonstrated recruitment of various anterior medial cortical regions including the anterior cingulate cortex (ACC) in healthy subjects during auditory perception of self-related stimuli. We further showed that patients with DOC showed signal changes in the ACC during auditory perception of self-related stimuli. Finally, it was shown that these signal changes correlate with the level of consciousness in the patients with DOC.

CONCLUSION

The degree of consciousness in patients with DOC was correlated with neural activity in the ACC induced by self-related stimuli. Our results not only shed light on the pathophysiology of DOC, but may also suggest a useful neural, and thus diagnostic, marker of the dysfunction of consciousness in vegetative patients.

Persistent vegetative and minimally conscious states

The diagnosis and management of patients with persistent vegetative (PVS) and minimally conscious (MCS) states entail powerful medical, ethical and legal debates. The recent description of the MCS highlights the crucial role of unexpected and well-documented recoveries of cognitive functions. Functional neuroimaging has provided new insights for assessing neuropathology and cerebral activity in these patients, providing information on the presence, degree, and location of any residual brain function in patients with PVS or MCS. We present a review on this topic, emphasizing the clinical and neuroimaging assessment of these states, with some of our recent results in this area. We conclude that the development of rehabilitation techniques for patients with PVS and others suffering long-lasting effects of brain injury is a crucial challenge for actual and future generations of neuroscientists.

Neuroimaging after coma

Following coma, some patients will recover wakefulness without signs of consciousness (only showing reflex movements, i.e., the vegetative state) or may show non-reflex movements but remain without functional communication (i.e., the minimally conscious state). Currently, there remains a high rate of misdiagnosis of the vegetative state (Schnakers et. al. BMC Neurol, 9:35, 8) and the clinical and electrophysiological markers of outcome from the vegetative and minimally conscious states remain unsatisfactory. This should incite clinicians to use multimodal assessment to detect objective signs of consciousness and validate para-clinical prognostic markers in these challenging patients. This review will focus on advanced magnetic resonance imaging (MRI) techniques such as magnetic resonance spectroscopy, diffusion tensor imaging, and functional MRI (fMRI studies in both "activation" and "resting state" conditions) that were recently introduced in the assessment of patients with chronic disorders of consciousness.

Improving the clinical assessment of consciousness with advances in electrophysiological and neuroimaging techniques

In clinical neurology, a comprehensive understanding of consciousness has been regarded as an abstract concept - best left to philosophers. However, times are changing and the need to clinically assess consciousness is increasingly becoming a real-world, practical challenge. Current methods for evaluating altered levels of consciousness are highly reliant on either behavioural measures or anatomical imaging. While these methods have some utility, estimates of misdiagnosis are worrisome (as high as 43%) - clearly this is a major clinical problem. The solution must involve objective, physiologically based measures that do not rely on behaviour. This paper reviews recent advances in physiologically based measures that enable better evaluation of consciousness states (coma, vegetative state, minimally conscious state, and locked in syndrome). Based on the evidence to-date, electroencephalographic and neuroimaging based assessments of consciousness provide valuable information for evaluation of residual function, formation of differential diagnoses, and estimation of prognosis.

Heart Rate Variability, Emotions, and Music

The purpose of the study was to identify significant changes in heart rate variability (an emerging descriptor of emotional conditions; HRV) concomitant to complex auditory stimuli with emotional value (music). In healthy controls, traumatic brain injured (TBI) patients, and subjects in the vegetative state (VS) the heart beat was continuously recorded while the subjects were passively listening to each of four music samples of different authorship. The heart rate (parametric and nonparametric) frequency spectra were computed and the spectra descriptors were processed by data-mining procedures. Data-mining sorted the nu_lf (normalized parameter unit of the spectrum low frequency range) as the significant descriptor by which the healthy controls, TBI patients, and VS subjects’ HRV responses to music could be clustered in classes matching those defined by the controls and TBI patients’ subjective reports. These findings promote the potential for HRV to reflect complex emotional stimuli and suggest that residual emotional reactions continue to occur in VS. HRV descriptors and data-mining appear applicable in brain function research in the absence of consciousness.

Functional Neuroimaging Approaches to the Changing Borders of Consciousness

The bedside diagnosis of vegetative and minimally conscious patients is extremely challenging, and prediction of individual long-term outcome remains difficult. State-of the art neuroimaging methods could help disentangle complex cases and offer new prognostic criteria. These methods can be divided into to three categories: First, new anatomical MRI neuroimaging methods, like diffusion tensor imaging (DTI) or spectroscopy, and passive functional imaging methods (looking at the brain’s activation induced by external stimuli), could provide new diagnostic and prognostic markers. Second, neuroimaging methods based on active collaboration from the patient could help to detect clinically unnoticed signs of consciousness. Third, developments in brain-computer interfaces based on EEG, functional MRI, or EMG offer communication possibilities in brain-damaged patients who can neither verbally nor nonverbally express their thoughts or wishes. These new approaches raise important issues not only from a clinical and ethical perspective (i.e., patients’ diagnosis, prognosis and management) but also from a neuroscientific standpoint, as they enrich our current understanding of the emergence and function of the conscious human mind.

Diagnosing consciousness: neuroimaging, law, and the vegetative state

In this paper, we review recent neuroimaging investigations of disorders of consciousness and different disciplines' understanding of consciousness itself. We consider potential tests of consciousness, their legal significance, and how they map onto broader themes in U.S. statutory law pertaining to advance directives and surrogate decision-making. In the process, we outline a taxonomy of themes to illustrate and clarify the variance in state-law definitions of consciousness. Finally, we discuss broader scientific, ethical, and legal issues associated with the advent of neuroimaging for disorders of consciousness and conclude with policy recommendations that could help to mitigate confusion in this realm.

The Vegetative State Updated

The vegetative state is characterized by the absence of awareness, voluntary or otherwise purposeful behavioral responses to external stimuli, and communication in the severely brain damaged. It is thought to result from an anatomical/functional disconnection between the brainstem and cortex as a result of diffuse axonal damage/impairment. Early assistance/rehabilitation and the logistic and medical/paramedical resources made available in the 1990s have improved survival and outcome. About 80% of posttraumatic patients recover consciousness (50–60% within 3–4 months and about 60% with good recovery at discharge) so long-term observation has become possible and changed our perspectives. Responsiveness to pain or emotional stimuli and brain processing at varying levels of functional complexity have been documented by advanced fMRI, PET, and electrophysiological studies. The evidence indicates retained regional connectivity and partial functional integrity in the absence of the integrative processes necessary to consciousness. Evolution into a minimally conscious state is common and preliminary to recovery and is observable even after 1–5 years. The boundaries between the vegetative and minimally conscious states are somehow blurred and experience suggests sequential phases in a recovery process, rather than independent conditions. Systematic investigation on the vegetative and minimal conscious states pathophysiology and a close revision of the nosographic and diagnostic criteria are warranted.

Towards the routine use of brain imaging to aid the clinical diagnosis of disorders of consciousness

Clinical audits have highlighted the many challenges and dilemmas faced by clinicians assessing persons with disorders of consciousness (vegetative state and minimally conscious state). The diagnostic decision-making process is highly subjective, dependent upon the skills of the examiner and invariably dictated by the patients' ability to move or speak. Whilst a considerable amount has been learnt since Jennett and Plum coined the term 'vegetative state', the assessment process remains largely unchanged; conducted at the bedside, using behavioural assessment tools, which are susceptible to environmental and physiological factors. This has created a situation where the rate of misdiagnosis is unacceptably high (up to 43%). In order to address these problems, various functional brain imaging paradigms, which do not rely upon the patient's ability to move or speak, have been proposed as a source of additional information to inform the diagnostic decision making process. Although accumulated evidence from brain imaging, particularly functional magnetic resonance imaging (fMRI), has been encouraging, the empirical evidence is still based on relatively small numbers of patients. It remains unclear whether brain imaging is capable of informing the diagnosis beyond the behavioural assessment and whether brain imaging has any prognostic utility. In this study, we describe the functional brain imaging findings from a group of 41 patients with disorders of consciousness, who undertook a hierarchical speech processing task. We found, contrary to the clinical impression of a specialist team using behavioural assessment tools, that two patients referred to the study with a diagnosis of vegetative state did in fact demonstrate neural correlates of speech comprehension when assessed using functional brain imaging. These fMRI findings were found to have no association with the patient's behavioural presentation at the time of investigation and thus provided additional diagnostic information beyond the traditional clinical assessment. Notably, the utility of brain imaging was further underlined by the finding that the level of auditory processing revealed by functional brain imaging, correlated strongly (rs = 0.81, P < 0.001) with the patient's subsequent behavioural recovery, 6 months after the scan, suggesting that brain imaging may also provide valuable prognostic information. Although further evidence is required before consensus statements can be made regarding the use of brain imaging in clinical decision making for disorders of consciousness, the results from this study clearly highlight the potential of imaging to inform the diagnostic decision-making process for persons with disorders of consciousness.

[Ethical aspects of dealing with coma patients]

The number of patients who survive severe brain injury increased due to progress in neurosurgery and intensive care. To establish a proper prognosis on the coma stage and the possible potential of remission is difficult in many cases. The treatment of patients in chronic coma leads to economic and ethical problems. Progress in functional radiology may help to obtain a proper prognosis in future. While numerous issues deal with ethical aspects in case of brain death only few do so with treatment decisions in chronic coma patients.

Changes in responsiveness when brain injury survivors with impaired consciousness hear different voices

PRIMARY OBJECTIVE

The researchers sought to determine whether individuals with impaired consciousness secondary to acquired brain injury (ABI) changed in responsiveness when purposefully presented with familiar, unfamiliar and synthetic voice messages.

RESEARCH DESIGN

Researchers used an ABA single case study design across stimuli. Participants were three minimally-responsive ABI survivors.

METHODS AND PROCEDURES

Participants heard auditory stimuli twice daily for 30 days. Data from video recordings included tallies of behavioural responses at 10-second intervals throughout baseline, intervention and post-intervention phases of each session. Statistical calculations allowed determination of responsiveness changes across time intervals within sessions.

MAIN OUTCOMES AND RESULTS

Unique response profiles emerged across survivors. Two participants demonstrated responsiveness changes with presentation of auditory stimuli. None demonstrated a clinically-significant differential response based on voice type.

CONCLUSIONS

Findings suggest that auditory stimulation results in arousal changes in some ABI survivors, regardless of the familiarity of voices presented.

Chronic consciousness disorders

Although philosophers and cognitive neuroscientists have struggled to define human consciousness, physicians can identify and assess its two clinical dimensions: wakefulness and awareness. A comatose patient has neither wakefulness nor awareness; a patient in a vegetative state has wakefulness without awareness; and a minimally conscious patient has both, but awareness is impaired. Syndromes of unconsciousness have established diagnostic criteria, but they encompass a spectrum of severity of brain damage and have indistinct boundaries. Functional neuroimaging using PET and fMRI have provided a new and complementary way to assess consciousness. Several recent provocative studies suggest that fMRI in unresponsive patients may detect evidence of conscious awareness when a careful neurological examination cannot. If these findings are verified by future studies, functional neuroimaging technologies will alter clinical practices concerning the diagnosis, classification, and prognosis of unconscious patients, and will lead to a greater understanding of the biology of human consciousness.

A technology-assisted learning setup as assessment supplement for three persons with a diagnosis of post-coma vegetative state and pervasive motor impairment

Post-coma persons in an apparent condition of vegetative state and pervasive motor impairment pose serious problems in terms of assessment and intervention options. A technology-based learning assessment procedure might serve for them as a diagnostic supplement with possible implications for rehabilitation intervention. The learning assessment procedure adopted in this study relied on hand-closure and eye-blinking responses and on microswitch technology to detect such responses and to present stimuli. Three participants were involved in the study. The technology consisted of a touch/pressure sensor fixed on the hand or an optic sensor mounted on an eyeglasses' frame, which were combined with a control system linked to stimulus sources. The study adopted an ABABCB sequence, in which A represented baseline periods, B intervention periods with stimuli contingent on the responses, and C a control condition with stimuli presented non-contingently. Data showed that the level of responding during the B phases was significantly higher than the levels observed during the A phases as well as the C phase for two of the three participants (i.e., indicating clear signs of learning by them). Learning might be deemed to represent basic levels of knowledge/consciousness. Thus, detecting signs of learning might help one revise a previous diagnosis of vegetative state with wide implications for rehabilitation perspectives.

Cerebral response to speech in vegetative and minimally conscious states after traumatic brain injury

PRIMARY OBJECTIVE

To study cerebral response in a functional magnetic resonance imaging (fMRI) task of speech perception in a sample of patients in vegetative state (VS) and minimally conscious state (MCS) after traumatic brain injury.

METHODS

Three patients in VS, four patients in MCS and 19 healthy volunteers were enrolled for the study. All subjects underwent an fMRI task of passive listening of narratives played forward and backward, alternated with periods of silence. This study analysed cerebral response to language and to complex sound processing in the healthy subjects' group and in each patient, using SPM5.

RESULTS

One patient in VS and one in MCS showed cerebral responses to language and to complex sound very similar to those shown by the healthy volunteers. Two more patients, one in VS and one in MCS, showed significant responses to complex sound only. Finally, one patient in VS and one patient in MCS failed to show significant activation in response to either stimulus.

CONCLUSIONS

Some patients in VS and MCS can preserve cerebral responses to language and auditory stimuli. fMRI may be useful to identify these responses, which may pass unnoticed in a bedside examination.

Applications of real-time fMRI

For centuries people have aspired to understand and control the functions of the mind and brain. It has now become possible to image the functioning of the human brain in real time using functional MRI (fMRI), and thereby to access both sides of the mind-brain interface--subjective experience (that is, one's mind) and objective observations (that is, external, quantitative measurements of one's brain activity)--simultaneously. Developments in neuroimaging are now being translated into many new potential practical applications, including the reading of brain states, brain-computer interfaces, communicating with locked-in patients, lie detection, and learning control over brain activation to modulate cognition or even treat disease.

Is there anybody in there? Detecting awareness in disorders of consciousness

The bedside detection of awareness in disorders of consciousness (DOC) caused by acquired brain injury is not an easy task. For this reason, differential diagnosis using neuroimaging and electrophysiological tools in search for objective markers of consciousness is being employed. However, such tools cannot be considered as diagnostic per se, but as assistants to the clinical evaluation, which, at present, remains the gold standard. Regarding therapeutic management in DOC, no evidence-based recommendations can be made in favor of a specific treatment. The present review summarizes clinical and paraclinical studies that have been conducted with neuroimaging and electrophysiological techniques in search of residual awareness in DOC. We discuss the medical, scientific and ethical implications that derive from these studies and we argue that, in the future, the role of neuroimaging and electrophysiology will be important not only for the diagnosis and prognosis of DOC but also in establishing communication with these challenging patients.

Brain damage and the moral significance of consciousness

Neuroimaging studies of brain-damaged patients diagnosed as in the vegetative state suggest that the patients might be conscious. This might seem to raise no new ethical questions given that in related disputes both sides agree that evidence for consciousness gives strong reason to preserve life. We question this assumption. We clarify the widely held but obscure principle that consciousness is morally significant. It is hard to apply this principle to difficult cases given that philosophers of mind distinguish between a range of notions of consciousness and that is unclear which of these is assumed by the principle. We suggest that the morally relevant notion is that of phenomenal consciousness and then use our analysis to interpret cases of brain damage. We argue that enjoyment of consciousness might actually give stronger moral reasons not to preserve a patient's life and, indeed, that these might be stronger when patients retain significant cognitive function.

Residual Brain Processing in the Vegetative State

Vegetative state (VS) is a clinical condition in the severely brain damaged, characterized by wakefulness but unaccompanied by any evidence of awareness of self or environment, voluntary or purposeful behavioral responses to external stimuli, and communication. A metabolic dysfunction of the frontal-parietal network is thought to be responsible for the “functional disconnection” underlying it. Most subjects recover with or without residual disabilities depending on the extent of brain damage. However, VS persists for over 1 year in about 15% of all cases, with exceptional later recovery; prolonged observation has thus become possible and our perspectives have expanded substantially. In recent years, brain activation in response to painful or emotional stimuli (e.g., the mother’s voice or presence) or under stimulus conditions implying processing at varying levels of functional complexity (including learning and semantic functions) has been documented in unambiguously diagnosed VS subjects by advanced electrophysiological and neuroimaging techniques. Methods, experimental conditions, and the results of studies published in years 2002–2008 are summarized. The extent to which brain activation concomitant to external events reflect brain function remains to be investigated. Today, VS nevertheless appears neither static nor homogeneous. An updated characterization also taking the evidence of residual brain responsiveness into account is due. Research with advanced technologies and sophisticated paradigms of brain activation in VS may help us to understand the basic neural processes underlying human consciousness.

A new era of coma and consciousness science

In the past ten years, rapid technological developments in the field of neuroimaging have produced a cornucopia of new techniques for examining both the structure and function of the human brain in vivo. In specialized centers, many of these methods are now being employed routinely in the assessment of patients diagnosed with disorders of consciousness, mapping patterns of residual function and dysfunction and helping to reduce diagnostic errors between related conditions such as the vegetative and minimally conscious states. Moreover, such efforts are beginning to provide important new prognostic indicators, helping to disentangle differences in outcome on the basis of a greater understanding of the underlying mechanisms responsible and providing information that will undoubtedly contribute to improved therapeutic choices in these challenging populations. Of course, these emerging technologies and the new information that they provide will bring new ethical challenges to this area and will have profound implications for clinical care and medical-legal decision-making in this population of patients. We review the most recent work in this area and suggest that the future integration of emerging neuroimaging techniques with existing clinical and behavioral methods of assessment will pave the way for new and innovative applications, both in basic neuroscience and in clinical practice.

Executive functions in the absence of behavior: functional imaging of the minimally conscious state

One of the major challenges in the clinical evaluation of brain injury survivors is to comprehensively assess the level of preserved cognitive function in order to inform diagnostic decisions and suggest appropriate rehabilitation strategies. However, the limited (if any) capacity for producing behavior in some of these patients often limits the extent to which cognitive functions can be explored via standard bedside methods. We present a novel neuroimaging paradigm that allows the assessment of residual executive functions without requiring the patient to produce any behavioral output. In particular, we target processes such as active maintenance of information through time and willful adoption of "mind-sets" that have been proposed to require conscious awareness. Employing an fMRI block design paradigm, healthy volunteers were presented with a series of neutral (i.e., not emotionally salient) words, and alternatively instructed to listen to all the words, or to count the number of times a given target is repeated. Importantly, the perceptual stimulation in the passive listening and the counting tasks was carefully matched. Contrasted with passive listening, the counting task revealed a fronto-parietal network previously associated with target detection and working memory. Remarkably, when tested on this same procedure, a minimally conscious patient presented a highly similar pattern of activation. Furthermore, the activity in these regions appeared highly synchronous to the onset and offset of the counting blocks. Considering the close matching of sensory stimulation across the two tasks, these findings strongly suggest that the patient could willfully adopt differential "mind-sets" as a function of condition, and could actively maintain information across time. Neither cognitive function was apparent when the patient was (behaviorally) tested at the bedside. This paradigm thus exemplifies the potential for fMRI to explore high-level cognitive functions, and awareness, in the absence of any behavioral response.

A multimodal approach to the assessment of patients with disorders of consciousness

Unlike other neurological conditions, the heterogeneous pathology linked to disorders of consciousness currently excludes a distinction between the vegetative and minimally conscious states based upon pathological presentation. The clinical assessment is therefore made on the basis of the patient's clinical history and exhibited behaviour. This creates a particular challenge for the clinician who has to decide whether a certain behaviour, which might be inconsistent or incomplete, reflects a conscious or an unconscious process. In an alarmingly high number of cases, identified during clinical audit, this decision process has been shown to be particularly fallible. The behavioural assessment is not only highly subjective, but also dependent upon the ability of the patient to move or speak; it is the only way someone can demonstrate they are aware. To address this problem we propose a multimodal approach, which integrates objective tools, such as electrophysiology and functional brain imaging, with traditional behavioural scales. Together this approach informs the clinical decision process and resolves many of the dilemmas faced by clinicians interpreting solely behavioural indices. This approach not only provides objective information regarding the integrity of residual cognitive function, but also removes the dependency on the patient to move or speak by using specially designed paradigms that do not require a motor output in order to reveal awareness of self or environment. To demonstrate this approach we describe the case of BW, who sustained a traumatic brain injury seven months prior to investigation. BW was admitted to a five-day assessment programme, which implemented our multimodal approach. On behavioural assessment BW demonstrated evidence of orientation and visual pursuit. However, he showed no response to written or verbal command, despite holding command cards and scanning text. Electrophysiology confirmed that he retained a preserved neural axis supporting vision and hearing, and suggested some evidence that he was able to create a basic memory trace. A hierarchical fMRI auditory paradigm suggested he was able to perceive sound and speech, but revealed no evidence of speech comprehension or ability to respond to command. This was corroborated in the visual modality using a hierarchical paradigm demonstrating that he was able to perceive motion, objects and faces, but retained no evidence of being able to respond to command. We briefly review work by other teams advocating the use of brain imaging and electrophysiology and discuss the steps that are now required in order to create an international standard for the assessment of persons with impaired consciousness after brain injury.

Mismatch negativity to the patient's own name in chronic disorders of consciousness

Previous studies implicated potential value of mismatch negativity (MMN) in predicting recovery of consciousness in patients with disorders of consciousness (DOC). We have adopted a novel MMN evoked by subject's own name (SON), a self-referential stimulus thought to be powerful in evoking residual brain activity, and examined the correlation between the MMN and recovery of consciousness in patients with chronic (>1 month) DOC. Twelve patients and 12 age-matched healthy controls were investigated. The patients were diagnosed as coma (n=4), vegetative state (VS, n=6), and minimally conscious state (MCS, n=2), mainly based on the JFK Coma Recovery Scale-Revised. The SON-evoked MMN (SON-MMN) was present in seven patients. Critically, the presence of SON-MMN was significantly correlated with recovery of consciousness. While four of the five patients (three VS and two coma) showing SON-MMN changed to MCS 3 months later, the rest of the patients (three VS and two coma) without SON-MMN failed to show any clinical improvement. Our study thus illustrates that the subject's own name is effective in evoking MMN in patients with DOC, and that SON-MMN has potential prognostic values in predicting recovery of consciousness.

Neuroimaging and disorders of consciousness: envisioning an ethical research agenda

The application of neuroimaging technology to the study of the injured brain has transformed how neuroscientists understand disorders of consciousness, such as the vegetative and minimally conscious states, and deepened our understanding of mechanisms of recovery. This scientific progress, and its potential clinical translation, provides an opportunity for ethical reflection. It was against this scientific backdrop that we convened a conference of leading investigators in neuroimaging, disorders of consciousness and neuroethics. Our goal was to develop an ethical frame to move these investigative techniques into mature clinical tools. This paper presents the recommendations and analysis of a Working Meeting on Ethics, Neuroimaging and Limited States of Consciousness held at Stanford University during June 2007. It represents an interdisciplinary approach to the challenges posed by the emerging use of neuroimaging technologies to describe and characterize disorders of consciousness.

Exploring impaired consciousness: the MRI approach

PURPOSE OF REVIEW

To summarize the application of advanced MRI sequences such as magnetic resonance spectroscopy, diffusion tensor imaging and functional MRI for the evaluation of patients with altered consciousness.

RECENT FINDINGS

Magnetic resonance spectroscopy, volumetry and diffusion tensor imaging have shown promising results in the evaluation of traumatic or anoxo-ischaemic brain lesions and can detect damage of the brainstem, basal ganglia and white matter tracts not visible on conventional sequences. A diffusion tensor imaging study has raised the possibility of detecting ongoing axonal regrowth many years after the initial injury in minimally conscious patients. Functional MRI studies have shown that a high level of brain activities, such as recognizing one's own name or imagining playing tennis, can be preserved in vegetative patients.

SUMMARY

The development of quantitative imaging could lead to a more objective evaluation of the extent of destruction or preservation of critical brain areas at the acute phase of brain injury, which could be integrated in multi-parametric decisional strategies for these patients. Functional imaging could help define borders between the various levels of altered consciousness and detect the presence of cryptic residual functions in vegetative or minimally conscious patients. This approach could eventually help determine the neurological outcome and make individual blueprints of the preserved brain activities in severely brain injured patients.

Personal Interaction in the Vegetative State

Background and purpose: Brain processing at varying levels of functional complexity and emotional reactions to relatives are anecdotally reported by the caregivers of patients in a vegetative state. In this study, computer-assisted machine-learning procedures were applied to identify heart rate variability changes or galvanic skin responses to a relative’s presence. Methods: The skin conductance (galvanic skin response) and heart beats were continuously recorded in 12 patients in a vegetative state, at rest (baseline) and while approached by a relative (usually the mother; test condition) or by a nonfamiliar person (control condition). The cardiotachogram (the series of consecutive intervals between heart beats) was analyzed in the time and frequency domains by computing the parametric and nonparametric frequency spectra. A machine-learning algorithm was applied to sort out the significant spectral parameter(s). For all patients, each condition (baseline, test, control) was characterized by the values of its spectral parameters, and the association between spectral parameters values and experimental condition was tested (WEKA machine-learning software). Results and comments: A galvanic skin response was obtained in two patients. The machine-learning procedure independently selected the nu_LF spectral parameter and attributed each nu_LF measure to any of the three experimental conditions. 69.4% of attributions were correct (baseline: 58%; test condition: 75%; control. 75%). In seven patients, attribution changed when the subject was approached by the test person; specifically, sequential shifts from baseline to test condition (“the Mom effect”) to control condition were identified in four patients (30.0%); the change from test to control was attributed correctly in seven patients (58%). The observation of heart rate changes tentatively attributable to emotional reaction in a vegetative state suggest residual rudimentary personal interaction, consistent with functioning limbic and paralimbic systems after massive brain damage. Machine-learning proved applicable to sort significant measure(s) out of large samples and to control for statistical alpha inflation.