brain : Steer simplicity

DAVID ADAM

Michael Schumacher is not so special. Throwing a Formula One car round corners at nearly 200 mph could be as simple as looking where you are going, researchers from Reading University in the UK now suggest. And they have a new computer model to prove it.

"Driving a car round a corner must be pretty simple as most of us don't even pay full attention," says psychologist John Wann. "We're usually chatting to friends or singing along to the radio." Schumacher may not be that relaxed, but Wann says everyone could learn how to take a corner as well as the racing driver.

In fact, many already have. Traffic police, motorcyclists and improving drivers are taught to look at the exit point of a curve, or at points on their intended path through tricky corners. Advanced driving manuals suggest that steering will then naturally proceed towards that point. Wann and his colleague David Swapp now explain why in Nature Neuroscience¹.

Most researchers assume that to steer the brain calculates our 'heading' (direction in a straight line) and then compares this with the line we need to take. If these differ then we change course -- the accuracy of these calculations determines whether we negotiate the corner or finish in the next field. This requires a lot of neural processing.

But opinion zigzags like a learner driver on just how much information the brain needs to judge heading. Some argue that the eyes are sufficient, others that the brain is easily fooled into thinking it is moving -- when watching roller coaster footage for example -- and say that extra movement input is required.

Wann and Swapp offer a new steering model that makes such arguments irrelevant. Provided drivers look at their destination, they say, retinal images alone are enough to steer -- the information does not need to be processed into 'heading'. This particular by-pass is quick, easy and available to all. Taking a bend becomes a simple matter of picking the right spot to watch.

Science fiction fans have the best chance of understanding why. Stars streak out when spacecraft are shown accelerating to light speed. When the Millennium Falcon turns sharp left the stars appear to flow to the right. These stellar lines can represent how images 'flow' across the retina: look dead ahead while moving forwards and flow lines are straight, glance to the side and they tilt.

If drivers focus at a point on a curve, then it appears at the centre of this display. Flow lines then show if the car will pass through that point. Steer too sharply on a left-hand bend, for example, and flow lines turn to the right. This instant feedback allows the brain to judge future paths without knowing 'heading' the researchers say.

Frank Bremmer, a neurobiologist who studies motion perception at Ruhr University in Bochum, Germany says that the new theory combines several previously held views. Unpublished work from his laboratory agrees with this model, he says, though he is not convinced it is accurate for all situations. "You cannot rule out that heading information is used. It is available and the brain makes use of all available information," he says.

1. Wann, J. P. & Swapp, D. K. Why you should look where you are going. Nature Neuroscience 3, 647-649 (2000).