Researchers have found hidden signatures in the brains of people in vegetative states that could point to consciousness.

The findings suggest patients in vegetative states are aware even if they are unable to communicate, the University of Cambridge reported.

Researchers used a functional magnetic resonance imaging (fMRI) scanner to monitor the pre-motor cortex to watch unconscious patients imagine playing a game of tennis.

A research team  also used high-density electroencephalographs (EEG) and a branch of mathematics known as "graph theory" to look at the brain networks of activity in 32 patients diagnosed as being in a vegetative state and compared this data with that from healthy adults. The researchers found the connections in the brain that normally support awareness are not always completely impaired in patients in a vegetative state. Some of these patients were found to maintain well-preserved brain networks that suggested "hidden awareness."

"Understanding how consciousness arises from the interactions between networks of brain regions is an elusive but fascinating scientific question. But for patients diagnosed as vegetative and minimally conscious, and their families, this is far more than just an academic question - it takes on a very real significance. Our research could improve clinical assessment and help identify patients who might be covertly aware despite being uncommunicative," said Srivas Chennu from the Department of Clinical Neurosciences at the University of Cambridge.

The findings could help researchers better determine which patients have retained some level of awareness and which are in a completely vegetative state.

"Although there are limitations to how predictive our test would be used in isolation, combined with other tests it could help in the clinical assessment of patients," said Tristan Bekinschtein from the MRC Cognition and Brain Sciences Unit and the Department of Psychology, University of Cambridge.

The research was published in a recent edition of the journal PLOS Computational Biology.