Novelist Isaac B. Singer once said, "We must believe in free will, we have no choice." Now, a new study has suggested that free will indeed exists -- in a place towards the back of the human brain.

Researchers at Cognitive Neuroscience Centre in France have carried out the study and found that free will resides in the parietal cortex of the human brain, according to a report in New Scientist.

Their findings are based on an analysis of an experiment on seven patients undergoing brain surgery to remove tumours. The scientists found that when they electrically jolted the parietal cortex in the patients undergoing surgery, the patients felt a desire to wiggle their finger, for instance; roll their tongue or move a limb.

Stronger electrical pulses convinced patients that they had actually performed these movements, although their bodies did not move. "What it tells us is there are specific brain regions that are involved in the consciousness of your movement," said Angela Sirigu, who led the study.

In all but one case, the cancers were located far from the parietal cortex and other areas. One patient's tumour was located near the parietal cortex, but it did not interfere with the experiments.

Because the patients were awake during the surgery, they were able to answer questions. "Did you move?" the researchers asked a 76-year-old man after lightly zapping a point on his parietal cortex. "No," he responded. "I had a desire to roll my tongue in my mouth."

After a stronger pulse to the parietal cortex, a 42-year-old man exclaimed: "My hand moved," yet Sirigu's team saw no signs of movement. The scientists also discovered stimulating another brain area -- the premotor cortex -- provoked involuntary, unconscious movements in the same patients.

The study points to two brain areas involved in the decision to move a limb and then execute the action. Sirigu speculates that the parietal cortex makes predictions about future movements and sends instructions to the premotor cortex, which returns the outcome of the movement to the parietal cortex.

"In day-to-day life, we rely on both brain regions to move about. You need both systems, the parietal and premotor cortex to generate intention and check whether this is followed through," Sirigu said.

The findings are published in the journal Science.