There are two distinct neural networks that work together to create the sensation of pain. The more basic of the two - the sensory-discriminative network - identifies the presence of an unpleasant stimulus. It is the affective network that attaches emotions and subjective feelings to the experience.
Without the activity of the emotional network, your brain detects pain but won't interpret it as unpleasant.
Using PET scans, previous studies have detected activation in the sensory-discriminative network in people with UWS but their findings were consistent with a lack of subjective awareness, the hallmark of the condition.
Now Markl and her colleagues have found evidence of activation in the affective or emotional network too.
Her team gave moderately painful electric shocks to 30 people with UWS, while scanning their brains using fMRI. Sixteen people had some kind of brain activation - seven only in the sensory network but nine in the affective network as well.
These results question whether some diagnoses should change from UWS to minimally conscious, which is characterised by some level of awareness.
Donald Weaver at Dalhousie University in Halifax, Nova Scotia, Canada, who was not involved in the work, doesn't think that this paper alone will change the clinical approach to people with diagnoses such as UWS, but hopes that it will encourage future study.
Changing a diagnosis depends on whether neurologists are ready to accept alternative ways of diagnosing disorders of consciousness, noted Boris Kotchoubey at the Institute of Medical Psychology and Behavioural Neurobiology in Tubingen, Germany, who worked on the study.
However, Kotchoubey is confident that the way people with UWS are cared for will change, even if their diagnoses remain the same.