The researchers believe that the signal identified by them may also be helpful in refining pain-relief techniques that involve stimulating the brain with electricity.
Morten Kringelbach of the psychiatry department at the university has revealed that the discovery is based on low-frequency brain waves that emanate from two regions buried deep within the brain when a patient is in pain.
He says the more the pain, the longer the waves last.
"It is an objective measure that correlates with a subjective measure," Nature quoted Kringelbach, as saying.
The researchers recorded activity from two electrodes positioned in the thalamus and the periaqueductal grey area of 12 people, who had been undergoing deep-brain stimulation (DBS) for chronic pain.
While recording their brain activity, the researchers touched either a painful or pain-free area of the patients' bodies and had patients rate their pain every minute.
The researchers said the duration of the waves correlated with the intensity of pain the patients felt.
"It is an objective measure that correlates with a subjective measure," says Kringelbach, who presented the findings at the Society for Neuroscience meeting in San Diego, California.
Allan Basbaum, a neuroscientist at the University of California, San Francisco, said: "It would be great to have a 'signature of pain'."
The researcher are yet to determine whether these spindles disappear when painkillers, anaesthetics or electrical stimulation are used.
The next step in the research is to try to record the signals with a non-invasive technique, such as magnetoencephalography, which measures electrical activity in the brain via changes in the magnetic field. This could allow pain monitoring in a much broader range of patients.