Learning as a possible sign of non-reflective consciousness in persons with a diagnosis of vegetative state and pervasive motor impairment

Questioning the dichotomy between vegetative state and minimally conscious state: a review of the statistical evidence

Given the enormous consequences that the diagnosis of vegetative state (VS) vs. minimally conscious state (MCS) may have for the treatment of patients with disorders of consciousness, it is particularly important to empirically legitimate the distinction between these two discrete levels of consciousness. Therefore, the aim of this contribution is to review all the articles reporting statistical evidence concerning the performance of patients in VS vs. patients in MCS, on behavioral or neurophysiological measures. Twenty-three articles matched these inclusion criteria, and comprised behavioral, electroencephalographic (EEG), positron emission tomography (PET) and magnetic resonance imaging (MRI) measures. The analysis of these articles yielded 47 different statistical findings. More than half of these findings (n = 24) did not reveal any statistically significant difference between VS and MCS. Overall, there was no combination of variables that allowed reliably discriminating between VS and MCS. This pattern of results casts doubt on the empirical validity of the distinction between VS and MCS.

Microswitch-aided programs with contingent stimulation versus general stimulation programs for post-coma persons with multiple disabilities

OBJECTIVE

Assessing the impact of microswitch-aided programs with contingent stimulation on response engagement (Study I) and post-session alertness (Study II) of post-coma participants with multiple disabilities.

METHOD

Study I included three participants whose scores on the Coma Recovery Scale-Revised (CRS-R) were 11 or 13. Study II included three participants whose CRS-R scores were 19, 13, and 14. In both studies, the participants received sessions with contingent stimulation (i.e., sessions in which activation of a microswitch with an eyelid or hand response produced 15 s of preferred stimulation) and sessions with general, non-contingent stimulation (i.e., stimulation lasted throughout the sessions).

RESULTS

Study I showed an increase in response engagement/frequencies only during the contingent stimulation sessions. Study II showed that the participants' level of vigilance after those sessions was higher than after non-contingent stimulation sessions.

CONCLUSION

Microswitch-aided programs with contingent stimulation would be more beneficial than programs with general/non-contingent stimulation.

Assessing learning as a possible sign of consciousness in post-coma persons with minimal responsiveness

A learning test procedure based on operant principles may be useful in the diagnosis (and eventually rehabilitation) of post-coma persons with minimal responsiveness. This study was aimed at extending the evaluation of such a procedure with seven participants who presented with very limited behavior and apparently severe disorders of consciousness. The procedure was evaluated through an ABACB design, in which A represented baseline phases without stimulation, B intervention phases with brief stimulation periods contingent on specific responses of the participants, and C a control phase in which stimulation was available all the time. Increased responding during the B phases, as opposed to the A and C phases, was taken to indicate learning and possibly a non-reflective expression of phenomenal consciousness. All participants were also evaluated with the coma recovery scale-revised (CRS-R) prior to the start of the learning test procedure and at the end of it. The results of the learning test showed that all participants had significantly higher responding levels during the B phases. The CRS-R scores suggested minimally conscious state for four of them prior to the learning test and for five of them after the completion of the learning test. The implications of the findings are discussed in terms of potential and time cost of the learning test.

Dissociation of vegetative and minimally conscious patients based on brain operational architectonics: factor of etiology

Discrimination between patients in vegetative (VS) and minimally conscious state (MCS) is currently based upon the behavioral gold standard. Behavioral assessment remains equivocal and difficult to interpret as evidence for the presence or absence of consciousness, resulting in possible clinical misdiagnosis in such patients. Application of an operational architectonics (OA) strategy to electroencephalogram (EEG) analysis reveals that absence of consciousness in patients in VS is paralleled by significant impairment in overall EEG operational architecture compared to patients in MCS: neuronal assemblies become smaller, their life span shortened, and they became highly unstable and functionally disconnected (desynchronized). However, in a previous study, patients with different brain damage etiologies were intermixed. Therefore, the goal of the present study was to investigate whether the application of OA methodology to EEG could reliably dissociate patients in VS and MCS independent of brain damage etiology. We conclude that the observed EEG OA structure impairment in patients in VS and partial preservation in patients in MCS is a marker of consciousness/unconsciousness rather than physiological damage. Results of this study may have neuroscientific, clinical, and ethical implications.

Challenges of developing communicative interaction in individuals with congenital profound intellectual and multiple disabilities

BACKGROUND

Physiological responses have been used in individuals with acquired disability to enable communicative interaction without motor movement. This study explored four autonomic nervous system (ANS) signals-electrodermal activity, skin temperature, cardiac patterns and respiratory patterns-to enable interaction with individuals born with profound intellectual and multiple disabilities (PIMD).

METHOD

A series of case studies were conducted to teach a 15-year-old individual with PIMD to voluntarily control his ANS signals for the purposes of communicative interaction. Training was carried out according to an alternating treatment single-subject research design.

RESULTS

Training was unsuccessful; however, ANS signal patterns revealed issues unique to people with PIMD: profound intrasubject variability, discrepancy between physiological responses and caregiver perspectives, and the participant's lack of contingency awareness.

CONCLUSIONS

These three priority areas unique to people with congenital PIMD must be addressed before ANS signals can be used to enable communicative interaction with this population.

Two persons with multiple disabilities use camera-based microswitch technology to control stimulation with small mouth and eyelid responses

BACKGROUND

A camera-based microswitch technology was recently developed to monitor small facial responses of persons with multiple disabilities and allow those responses to control environmental stimulation. This study assessed such a technology with 2 new participants using slight variations of previous responses.

METHOD

The technology involved a computer with a CPU using a 2GHz clock, a USB video camera with 16-mm lens, and special software. Small colour spots were used under the lower lip of one participant and on the eyelid of the other participant to aid the camera and computer to detect their mouth and eyelid responses. The study involved an ABAB design and included a 3-week post-intervention check.

RESULTS

The participants' mouth and eyelid responses increased during the intervention (B) phases and post-intervention check (i.e., when the technology allowed them to control stimulation).

CONCLUSIONS

Camera-based microswitch technology can help persons with multiple disabilities control stimulation with small responses.

Promoting adaptive behavior in persons with acquired brain injury, extensive motor and communication disabilities, and consciousness disorders

These two studies extended the evidence on the use of technology-based intervention packages to promote adaptive behavior in persons with acquired brain injury and multiple disabilities. Study I involved five participants in a minimally conscious state who were provided with intervention packages based on specific arrangements of optic, tilt, or pressure microswitches (linked to preferred environmental stimuli) and eyelid, toe and finger responses. Study II involved three participants who were emerging from a minimally conscious state and were provided with intervention packages based on computer presentations of stimulus options (i.e., preferred stimuli, functional caregiver's procedures, and non-preferred stimuli) and pressure microswitches to choose among them. Intervention data of Study I showed that the participants acquired relatively high levels of microswitch responding (thus engaging widely with preferred environmental stimuli) and kept that responding consistent except for one case. Intervention data of Study II showed that the participants were active in choosing among preferred stimuli and positive caregivers' procedures, but generally abstained from non-preferred stimuli. The results were discussed in terms of the successful use of fairly new/infrequent microswitch-response arrangements (Study I) and the profitable inclusion of functional caregiver's procedures among the options available to choice (Study II).

Technology-based intervention to help persons with minimally conscious state and pervasive motor disabilities perform environmentally relevant adaptive behavior

Persons with a diagnosis of minimally conscious state and pervasive motor disabilities tend to be passive and isolated. A way to help them improve their adaptive behavior (relate to their environment) involves the use of intervention packages combining assistive technology with motivational strategies. The types of assistive technology included in those packages may consist of (a) microswitches allowing direct access to environmental stimuli, (b) combinations of microswitches and voice output communication devices (VOCAs) allowing stimulus access and calls for caregivers' attention, respectively, and (c) computer presentations of stimulus options and microswitches allowing choice among those options and access to them.

A learning assessment procedure as a test supplement for monitoring progress with two post-coma persons with a diagnosis of vegetative state

OBJECTIVE

Evaluating a learning assessment procedure for monitoring progress with two post-coma adults with a diagnosis of vegetative state.

METHOD

ABABCBCB and ABABCB designs were used for the two participants, with A representing baseline, B intervention and C control conditions. Participants' activation of an optic microswitch by eyelid closure produced stimulation during B phases.

RESULTS

One participant increased responding during B phases and decreased it during the C condition, suggesting a non-reflective minimal level of consciousness. She showed P300 and mismatch negativity responses and scored at the vegetative level on the Coma Recovery Scale-Revised (CRS-R). The other participant increased responding during the initial B phases without decline during the first (viable) part of the C condition, suggesting a pre-conscious level. He showed indistinct P300 and mismatch negativity responses and vegetative-level scores on the CRS-R.

CONCLUSION

Learning data seemed reconcilable with neurophysiological measures and more positive than CRS-R scores.

Microswitch technology and contingent stimulation to promote adaptive engagement in persons with minimally conscious state: a case evaluation

This study assessed whether a post-coma woman functioning at the lower end of the minimally conscious state would (a) develop adaptive responding through the use of microswitch technology and contingent stimulation, (b) consolidate and maintain her responding over time, and (c) show evidence of response-consequences awareness (learning and discrimination). The study involved an ABABB1CB1 sequence in which the A represented baseline phases, the B and B1 intervention phases, and the C a control phase with continuous stimulation. Results indicated that the woman developed adaptive responding and consolidated it over the intervention phases of the study. The woman also showed evidence of being aware of response-consequences links. Potential implications and limitations of these findings are discussed.

An overview of intervention options for promoting adaptive behavior of persons with acquired brain injury and minimally conscious state

This paper presents an overview of the studies directed at helping post-coma persons with minimally conscious state improve their adaptive behavior. Twenty-one studies were identified for the 2000-2010 period (i.e., a period in which an intense debate has occurred about diagnostic, rehabilitative, prognostic, and ethical issues concerning people with severe acquired brain injury). Three of the 21 studies involved transcortical magnetic or deep brain stimulation. Six studies focused on the provision of multisensory stimulation or music therapy. The remaining 12 studies involved the use of response-related (contingent) stimulation and assistive technology. The outcomes of the studies, which were generally reported as positive, were discussed in terms of (a) the size (quantitative relevance) of the changes obtained, (b) the credibility/reliability of the changes, in light of the methodological conditions of the studies, and (c) the level of engagement and interaction involvement of the participants. Relevant issues for future research were also examined.