Sunday, May 31, 2015

A trilogy on consciousness

Peterson A, Cruse D, Naci L, Weijer C, Owen AM. Risk, diagnostic error, and
the clinical science of consciousness. Neuroimage Clin. 2015 Feb 20;7:588-97.
In recent years, a number of new neuroimaging techniques have detected covert awareness in some patients previously thought to be in a vegetative state/unresponsive wakefulness syndrome. This raises worries for patients, families, and physicians, as it indicates that the existing diagnostic error rate in this patient group is higher than assumed. Recent research on a subset of these techniques, called active paradigms, suggests that false positive and false negative findings may result from applying different statistical methods to patient data. Due to the nature of this research, these errors may be unavoidable, and may draw into question the use of active paradigms in the clinical setting. We argue that false positive and false negative findings carry particular moral risks, which may bear on investigators' decisions to use certain methods when independent means for estimating their clinical utility are absent. We review and critically analyze this methodological problem as it relates to both fMRI and EEG active paradigms. We conclude by drawing attention to three common clinical scenarios where the risk of diagnostic error may be most pronounced in this patient group.

Naci L, Cusack R, Anello M, Owen AM. A common neural code for similar
conscious experiences in different individuals. Proc Natl Acad Sci U S A. 2014
Sep 30;111(39):14277-82.

The interpretation of human consciousness from brain activity, without recourse to speech or action, is one of the most provoking and challenging frontiers of modern neuroscience. We asked whether there is a common neural code that underpins similar conscious experiences, which could be used to decode these experiences in the absence of behavior. To this end, we used richly evocative stimulation (an engaging movie) portraying real-world events to elicit a similar conscious experience in different people. Common neural correlates of conscious experience were quantified and related to measurable, quantitative and qualitative, executive components of the movie through two additional behavioral investigations. The movie's executive demands drove synchronized brain activity across healthy participants' frontal and parietal cortices in regions known to support executive function. Moreover, the timing of activity in these regions was predicted by participants' highly similar qualitative experience of the movie's moment-to-moment executive demands, suggesting that synchronization of activity across participants underpinned their similar experience. Thus we demonstrate, for the first time to our knowledge, that a neural index based on executive function reliably predicted every healthy individual's similar conscious experience in response to real-world events unfolding over time. This approach provided strong evidence for the conscious experience of a brain-injured patient, who had remained entirely behaviorally nonresponsive for 16 y. The patient's executive engagement and moment-to-moment perception of the movie content were highly similar to that of every healthy participant. These findings shed light on the common basis of human consciousness and enable the interpretation of conscious experience in the absence of behavior.

Graham M, Weijer C, Peterson A, Naci L, Cruse D, Fernández-Espejo D,
Gonzalez-Lara L, Owen AM. Acknowledging awareness: informing families of
individual research results for patients in the vegetative state. J Med Ethics.
2014 Jul 30.

Recent findings in cognitive neuroscience have revealed that some patients previously diagnosed as being in a vegetative state may retain some degree of covert awareness. However, it is unclear whether such findings should be disclosed to the families of these patients. Concerns about the preservation of scientific validity, reliability of results and potential harms associated with disclosure suggest that individual research results should be disclosed only under certain conditions. In the following paper, we offer four criteria for the disclosure of individual research results. Because the results of functional neuroimaging studies to detect covert awareness in vegetative patients are scientifically valid, informative and reasonably reliable and have considerable potential benefit for the patient, researchers have an obligation to disclose such results to family members. Further work is needed to develop educational materials for families and to systematically study the impact of disclosure on the families themselves.

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