A new study has found that people use mind control to change images on a video screen based on their conscious thought.

Twelve Volunteers, who were bombarded with images, noise and smells, decided on what to select or ignore by changing the firing rates in individual brain cells. The volunteers had agreed for their brains to be wired to a computer.

The volunteers were shown pictures of Marilyn Monroe or Michael Jackson, around 110 familiar images an scientists identified individual neurons that uniquely and reliably responded to one of the images.

The research was conducted by Moran Cerf from the California Institute of Technology in Pasadena and the study was published in Nature.

The research is particularly exciting, says neuroengineer John Donoghue of Brown University, "because it shows how we can now peer into the process of thinking at a level we have not been able to get at before".

Donoghue was responsible for the first successful transplantation of a chip into the motor cortex of a tetraplegic man, enabling him to move a computer cursor and manipulate a robotic arm with his mind.

The volunteers suffered severe, treatment-resistant epilepsy, and were awaiting neurosurgery at the UCLA Ronald Reagan Medical Center in Los Angeles to remove the brain tissue responsible for initiating seizures.

The experiment shows how humans can use thinking to alter perception of competing visual images, says Cerf. "The environment offers some reality," he says, "but your own brain can shape it and override it with its internal deliberations."