They used this technology to allow people to answer questions with their mind only. To do so, they ask a yes/no question and ask the person to think about an activity for "yes" or an image for "no". Depending on the area of the brain which shows activity on the fMRI, they can determine the person's answer.
A nice parlor trick, until they turned the technology on patients in a so called "vegetative state". Out of 60 patients examined, 43% could respond to questions asked verbally. This is a significant find, and challenges whether patients are being diagnosed incorrectly, or whether we even understand what a "vegetative state" is.
A lot hangs in the balance here. In the UK it is legal to allow a patient in a vegetative state to die by withdrawing all care (including food and drink). However, if these patients are able to respond, are they really in a vegetative state? Of course even a "true" vegetative state does not make a person "not human", laws to the contrary notwithstanding. This research just points out how slippery the slope of euthanasia really is.