Detecting awareness in patients with disorders of consciousness using a hybrid brain–computer interface
; ; et al
in Journal of Neural Engineering (2014)
Objective. The bedside detection of potential awareness in patients with disorders of consciousness (DOC) currently relies only on behavioral observations and tests; however, the misdiagnosis rates in ... [more ▼]
Objective. The bedside detection of potential awareness in patients with disorders of consciousness (DOC) currently relies only on behavioral observations and tests; however, the misdiagnosis rates in this patient group are historically relatively high. In this study, we proposed a visual hybrid brain–computer interface (BCI) combining P300 and steady-state evoked potential (SSVEP) responses to detect awareness in severely brain injured patients. Approach. Four healthy subjects, seven DOC patients who were in a vegetative state (VS, n = 4) or minimally conscious state (MCS, n = 3), and one locked-in syndrome (LIS) patient attempted a command-following experiment. In each experimental trial, two photos were presented to each patient; one was the patientʼs own photo, and the other photo was unfamiliar. The patients were instructed to focus on their own or the unfamiliar photos. The BCI system determined which photo the patient focused on with both P300 and SSVEP detections. Main results. Four healthy subjects, one of the 4 VS, one of the 3 MCS, and the LIS patient were able to selectively attend to their own or the unfamiliar photos (classification accuracy, 66–100%). Two additional patients (one VS and one MCS) failed to attend the unfamiliar photo (50–52%) but achieved significant accuracies for their own photo (64–68%). All other patients failed to show any significant response to commands (46–55%). Significance. Through the hybrid BCI system, command following was detected in four healthy subjects, two of 7 DOC patients, and one LIS patient. We suggest that the hybrid BCI system could be used as a supportive bedside tool to detect awareness in patients with DOC. [less ▲]Detailed reference viewed: 21 (0 ULg)
Preserved Covert Cognition in Noncommunicative Patients With Severe Brain Injury?
; ; et al
in Neurorehabilitation and Neural Repair (2014)Detailed reference viewed: 26 (10 ULg)
Assessment of visual fixatio in vegetative and minimally conscious states
; ; et al
in BMC Neurology (2014), 14(147),
Background: Visual fixation plays a key role in the differentiation between vegetative state/unresponsive wakefulness (VS/UWS) syndrome and minimally conscious state (MCS). However, the use of different ... [more ▼]
Background: Visual fixation plays a key role in the differentiation between vegetative state/unresponsive wakefulness (VS/UWS) syndrome and minimally conscious state (MCS). However, the use of different stimuli changes the frequency of visual fixation occured in patients, thereby possibly affecting the accuracy of the diagnosis. In order to establish a standardized assessment of visual fixation in patients in disorders of consciousness (DOC), we compared the frequency of visual fixation elicited by mirror,a ball and a light. Method: Visual fixation was assessed in eighty-one post-comatose patients diagnosed with a MCS or VS/UWS. Occurrence of fixation to different stimuli was analysis used Chi-square testing. Result: 40 (49%) out of the 81 patients showed fixation to visual stimuli. Among those, significantly more patients (39, 48%) had visual fixation elicited by mirror compared to a ball (23, 28%) and mirror compared to a light (20, 25%).Conclusion: The use of a mirror during the assessment of visual fixation showed higher positive response rate, compared to other stimuli in eliciting a visual fixating response. Therefore, fixation elicited by a mirror can be a very sensitive and accurate test to differentiate the two disorders of consciousness. [less ▲]Detailed reference viewed: 16 (8 ULg)
Resting state activity in patients with disorders of consciousness.
Soddu, Andrea ; Vanhaudenhuyse, Audrey ; et al
in Functional Neurology (2011), 26(1), 37-43
Recent advances in the study of spontaneous brain activity have demonstrated activity patterns that emerge with no task performance or sensory stimulation; these discoveries hold promise for the study of ... [more ▼]
Recent advances in the study of spontaneous brain activity have demonstrated activity patterns that emerge with no task performance or sensory stimulation; these discoveries hold promise for the study of higher-order associative network functionality. Additionally, such advances are argued to be relevant in pathological states, such as disorders of consciousness (DOC), i.e., coma, vegetative and minimally conscious states. Recent studies on resting state activity in DOC, measured with functional magnetic resonance imaging (fMRI) techniques, show that functional connectivity is disrupted in the task-negative or the default mode network. However, the two main approaches employed in the analysis of resting state functional connectivity data (i.e., hypothesis-driven seed-voxel and data-driven independent component analysis) present multiple methodological difficulties, especially in non-collaborative DOC patients. Improvements in motion artifact removal and spatial normalization are needed before fMRI resting state data can be used as proper biomarkers in severe brain injury. However, we anticipate that such developments will boost clinical resting state fMRI studies, allowing for easy and fast acquisitions and ultimately improve the diagnosis and prognosis in the absence of DOC patients' active collaboration in data acquisition. [less ▲]Detailed reference viewed: 65 (16 ULg)
Anterior cingulate activity and the self in disorders of consciousness.
; ; et al
in Human Brain Mapping (2010), 31(12), 1993-2002
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 ... [more ▼]
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. [less ▲]Detailed reference viewed: 31 (4 ULg)