Using just the power of thought to control onscreen computer activity, subjects in a recent study led by neurosurgery professor Itzhak Fried, M.D., Ph.D have managed to choose to bring one of two merged images into sharp focus while making the other disappear. Not only were only a few brain cells found to be used when selecting one picture over another, but each cell appeared to have its own image preference.

In the study, 12 epileptic subjects had fine wires implanted in their brains to record seizure activity. The researchers concentrated their efforts on the area of the brain known for memory and the ability to recognize complex images, the medial temporal lobe. With the brain recordings being monitored by computer equipment, the subjects were asked to look at two superimposed pictures of familiar objects, places, animals or people and to concentrate on just one of the images, to try and make it fully visible and the other image faded away. Every one-tenth of one second, the display screen was refreshed with input from the brain.

The research team "first identified four brain cells with preferences for celebrities or familiar objects, animals or landmarks, and then targeted the recording electrodes to those cells." It was found that individual cells appeared to have image preferences, one taking a shine to a picture of Marilyn Monroe while another might prefer Michael Jackson.

Success in the image-switching game was found to depend on the subject's ability to "power up cells that preferred the target image and suppress cells that preferred the non-target image," with subjects managing to achieve a 70 per cent success rate over almost 900 attempts.

The research was undertaken to try and get a better understanding of how the brain works but thought-controlled computing holds the promise of helping paralyzed individuals to communicate or control prosthetic limbs. Dr. Debra Babcock, a program director at the National Institute of Neurological Disorders and Stroke (NINDS), said that "the remarkable aspects of this study are that we can concentrate our attention to make a choice by modulating so few brain cells and that we can learn to control those cells very quickly."

The study, which had part of its funding supplied by NINDS and the National Institute of Mental Health, has now been published in Nature, entitled "On-line, voluntary control of human temporal lobe neurons".