Progress in brain research
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The term 'locked-in'syndrome (LIS) describes a medical condition in which persons concerned are severely paralyzed and at the same time fully conscious and awake. The resulting anarthria makes it impossible for these patients to naturally communicate, which results in diagnostic as well as serious practical and ethical problems. Therefore, developing alternative, muscle-independent communication means is of prime importance. ⋯ As our procedure can be easily transferred to MRI-equipped clinical sites, it may constitute a simple and effective possibility for online detection of residual consciousness and for LIS patients to communicate basic thoughts and needs in case no other alternative communication means are available (yet)--especially in the acute phase of the LIS. Future research may focus on further increasing the efficiency and accuracy of fMRI-based BCIs by implementing sophisticated data analysis methods (e.g., multivariate and independent component analysis) and neurofeedback training techniques. Finally, the presented BCI approach could be transferred to portable fNIRS systems as only this would enable hemodynamically based communication in daily life situations.
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To investigate predictors of recovery from the vegetative state (VS) and minimally conscious state (MCS) after brain injury as measured by the widely used Disability Rating Scale (DRS) and to explore differences in rate of recovery and predictors of recovery during inpatient rehabilitation in patients with non-traumatic (NTBI) and traumatic brain injury (TBI). ⋯ Time post-injury and DRS score at enrollment are predictors of early recovery among patients with disorders of consciousness, depending on the outcome measure chosen. Etiology was also a significant predictor in some analyses, with traumatically injured patients recovering more than those with non-traumatic injuries. However, the hypothesized interaction between etiology and time post-injury did not reach significance in any of the analyses suggesting that, within the time frame studied, the decline in prognosis with the passage of time was similar in the two groups.
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Assessing the level of consciousness of noncommunicative brain-damaged patients is difficult, as one has to make inferences based on the patients' behavior. However, behavioral responses of brain-damaged patients are usually limited not only by their cognitive dysfunctions, but also by their frequent motor impairment. For these reasons, it is essential to resort to para-clinical markers of the level of consciousness. ⋯ Specifically, we emphasize the principled approach provided by the Integrated Information Theory of Consciousness (IITC). We describe the different conditions where the theory predicts markedly reduced states of consciousness, and discuss several technical and conceptual issues limiting its applicability to measuring the level of consciousness of individual patients. Nevertheless, we argue that some of the predictions of the theory are potentially testable using available imaging techniques.
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Pain management in severely brain-damaged patients constitutes a clinical and ethical stake. At the bedside, assessing the presence of pain and suffering is challenging due to both patients' physical condition and inherent limitations of clinical assessment. Neuroimaging studies support the existence of distinct cerebral responses to noxious stimulation in brain death, vegetative state, and minimally conscious state. ⋯ Women and religious caregivers reported more often that minimally conscious patients may experience pain. These results are discussed in terms of existing definitions of pain and suffering, the remaining uncertainty on the clinical assessment of pain as a subjective first-person experience and recent functional neuroimaging findings on nociceptive processing in disorders of consciousness. In our view, more research is needed to increase our understanding of residual sensation in vegetative and minimally conscious patients and to propose evidence-based medical guidelines for the management of possible pain perception and suffering in these vulnerable patient populations.
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When an observer is searching through the environment for a target, what are the consequences of not finding a target in a given environment? We examine this issue in detail and propose that the visual system systematically tags environmental information during a search, in an effort to improve performance in future search events. Information that led to search successes is positively tagged, so as to favor future deployments of attention toward that type of information, whereas information that led to search failures is negatively tagged, so as to discourage future deployments of attention toward such failed information. To study this, we use an oddball-search task, where participants search for one item that differs from all others along one feature or belongs to a different visual category, from the other stimuli in the display. ⋯ Second, we show that the effect is independent of the mode of presentation of stimuli: it happens with both serial and simultaneous stimuli presentation. Third, we show that, when using categorically defined oddballs as the search stimuli (find the face among houses or vice versa), the bias generalizes to unseen members of the "failed" category. Together, these findings support the idea that this inter-trial attentional biases arise from high-level, task-constrained, implicit assessments of performance, involving categorical associations between classes of stimuli and behavioral outcomes (success/failure), which are independent of attentional modality (temporal vs. spatial attention).