Thursday, February 21, 2013

Vegetative States

Functional brain imaging techniques have become a versatile tool for peering into brain and how its activity can manifest as behavior. Nervous system injuries can leave people with varying degrees of functionality and capability. Disabilities can be of the mind such as the inability to perform cognitive tasks like math or impair memory recall or formation. Other injuries can be of the body such as in paralysis or quadriplegia. Unfortunately when it comes to brain injuries, the resulting symptoms are never easily quantifiable. Diagnosis of such patients is complicated by the fact that “There is as yet no universally agreed definition of consciousness and, to an even greater extent, no definition of ‘self-consciousness’ or ‘sense of self/being’“ (Owen and Coleman, 2008). It is thus no surprise that misdiagnosis resulting from brain imaging techniques are as high as 43% (Andrews et al. 1996, Childs et al. 1993). The progression of neuroimaging techniques being used clinically to diagnose consciousness and the vegetative state requires neuroscientists themselves to step up and provide education to clinicians and patients about not only how neuroimaging works but also what it means.

Can fMRI determine consciousness? (Source)


The most commonly used form of neuroimagaing, fMRI, basically extracts information about where energy is being used the fastest in the brain. This in combination with an understanding of what various brain regions do, can provide insight about what it is the brain may be thinking about. It would follow that perhaps neuroimaging could be used as a measure of how conscious a person is whether or not they are visibly awake and moving. This is precisely the complication arising in the case of patients in the vegetative state that while unable to execute commands physically, may still be mentally intact and alert. A recent study asking patients to imagine various scenarios such as playing tennis or walking around a house (Boly et al. 2007) provides ample evidence that brain scans can pick up different responses in brain activity that is question specific. When it comes to applying these techniques to vegetative patients, things get complicated.

The first complication arises from a lack of understanding how fMRI works. Patients families may correlate fMRI activity to consciousness when this may not be the case. For example if a patient is capable of hearing but not thinking about what they have heard, an fMRI may indicate brain activity whenever the patient is spoken to. Thus being able to hear is not the same as being able to process what is heard. The second complication arises from how brain scans and their information should be treated medically and legally. Neuroscientists much take up responsibility in educating clinicians and lawyers about the reliability and accessibility of this technique. For example, using fMRI scans as evidence for consciousness in court may be tenuous due to the high proportion of false negatives that fMRI scans may produce (Owens and Campbell 2008). Thirdly neurosciences have a responsibility in promoting awareness of multi-approach testing for consciousness. Even in science, brain scans are normally used as but a part of behavioral testing. Other measures including EEGs and comprehensive mental evaluations are necessary for augmenting fMRI scans.

While neuroimaging represents a great step toward helping diagnose patients suffering from nervous system damage, there remains much more education and awareness that falls to the hands of neuroscientists, clinicans, lawyers, and patients to make it an efficacious technique for evaluating consciousness.

--Michael Jiang



Want to cite this post?
Jiang, M. (2012). Vegetative States. The Neuroethics Blog. Retrieved on , from http://www.theneuroethicsblog.com/2013/02/vegetative-states.html


Works Cited

Andrews, K., Murphy, L., Munday, R. & Littlewood, C. Misdiagnosis of the vegetative state: retrospective study in a rehabilitation unit. BMJ 313, 13–16 (1996).

Boly, M. et al. When thoughts become actions: an fMRI paradigm to study volitional brain activity in noncommunicative brain injured patients. Neuroimage 36, 979–992, 2007.

Childs, N. L., Mercer, W. N. & Childs, H. W. Accuracy of diagnosis of persistent vegetative state. Neurology 43, 1465–1467 (1993).

Owens, A. M., Coleman, M. R. Functional neuroimaging of the vegetative state. Nature Neuroscience Perspectives (9), 235-243 (2008).

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