Consciousness

Home » Clinical Assessment and Neuroimaging of Consciousness » The Difference between Vegetation and Consciousness

The Difference between Vegetation and Consciousness

In popular culture comas are practically common place. While a useful plot device in medical fiction, they’re significantly more important in real life as they offer the brain a chance to recover from severe damage caused by stroke, seizure, or traumatic injury. But if a coma is like a reset button for our brain, how how do we tell between those who are minimally conscious and those who are vegetative (that is to say, completely unaware) within a coma? The Glasgow Coma Score (a scale from 3-15, 15 being fully conscious) is commonly used in medical situations to score a patient’s conscious state. This is a satisfactory measure of ability, leaving those scored at 3 points considered severely unconsciousness.

But what does it mean to be vegetative? As the colloquialism would suggest, the blunt meaning of the term is one in which a person has the consciousness level of a vegetable and is entirely unaware of their surroundings. Patients considered vegetative are actually very difficult to distinguish from those minimally conscious using conventional methods. Vegetative states are those in which there is absolutely no awareness of surroundings, while minimally conscious states involve some inconsistent and temporary awareness of surroundings. While great definitions to keep a hold of, these are just that — definitions. Due to the incredibly subjective nature of consciousness to begin with, it is hard to discern a difference between the two. We choose between the two when examining a patient by observation, looking for overt signs of consciousness, but who among us is necessarily overt when conscious? Consciousness is not necessarily visible through behaviour in those who are in a minimally conscious state. In a 1996 as many as 40 percent of diagnoses one way or another in this area were rejected suggesting the margin for error in this area could be very high indeed (Andrews et al., 1996).

Unreliable observation of behaviour in diagnosis has led to the investigation and development of new techniques centred around electro physiology in unresponsive brain injury patients. One such investigation was carried out by Kotchoubey et al. (2013) examining the role of empathy in distinguishing between vegetative and minimally conscious states. Empathy is a subjective experience triggered by the emotions or experience of others, most strong when others feel pain. Sympathy is the ability to attempt understanding of another’s feelings, while empathy is the ability to experience and recall the very same feelings as others. We all experience empathy, both emotionally and electro physiologically. The most obvious physiological sign of empathy is sweat, present in tiny amounts on the skin’s surface, when shown a video of others in distress. Our mind and body mirrors distress when we are conscious, thus the paper investigated whether it was possible to use empathy to discern between vegetative and minimally conscious individuals. Recently Lang et al. found that healthy conscious humans experience changes in the area of the brains known as the “pain matrix” when played auditory cries of distress. It stands to reason, then, that a similar activation might be seen in minimally conscious individuals but not vegetative state individuals.

Kotchoubey et al found this to be true during their analysis. There was a significant difference, p<0.05 (meaning above chance, and with over a 95 percent accuracy), between the two groups demonstrating the potential of their technique as a diagnostic tool.

References

Kotchoubey, B., Merz, S., Lang, S., Markl, A., Müller, F., Yu, T., & Schwarzbauer, C. (2013). Global functional connectivity reveals highly significant differences between the vegetative and the minimally conscious state. Journal of neurology, 1-9.


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