A baseball pitched at more than 144.8 km per hour or a tennis ball swatted at even greater speeds leaves opponents mere split-seconds to ready themselves for a savvy return. So how can the human brain track such small objects travelling at such high speeds?
New research suggests that the brain can predict and map the path of an oncoming object faster than it processes incoming visual information.
"For the first time, we can see this sophisticated prediction mechanism at work in the human brain," study lead author Gerrit Maus, a postdoctoral fellow in psychology at the University of California, Berkeley, said in a university news release.
The researchers said it can take one-tenth of a second for the brain to process what the eye sees. That means, for example, that by the time the brain "catches up" with incoming visual information, a tennis ball moving toward a person at 193 km per hour would already have moved 15 feet closer. If people couldn't compensate for this, they'd be hit by oncoming objects much more frequently than they are, the researchers said.
How the brain engages
To make up for this delay, the brain appears to engage a "prediction mechanism" that pushes oncoming objects a bit forward in their expected trajectory, according to the new study.
"The image that hits the eye and then is processed by the brain is not in sync with the real world, but the brain is clever enough to compensate for that," Maus said. "What we perceive doesn't necessarily have that much to do with the real world, but it is what we need to know to interact with the real world."
Maus's team said the findings provide deeper understanding of how people anticipate the trajectory of moving objects. Besides giving us a better understanding of how top athletes perform so well, the new insight could help doctors diagnose and treat many disorders, including those that impair motion perception.
The study involved six people who underwent functional MRI scans, in which brain activity is tracked in real time. During the scans, they viewed a two-part visual illusion in which they saw brief flashes shifting in the direction of motion, called the "flash-drag effect."
People's delayed visual-processing abilities
Using this technology, the researchers were able to pinpoint a region of the brain, called V5, that makes calculations to compensate for people's delayed visual-processing abilities.
"[The brain] engages its prediction mechanism to compensate for processing delays," Maus said. "Now, not only can we see the outcome of prediction in area V5, but we can also show that it is causally involved in enabling us to see objects accurately in predicted positions."
The study's authors said their findings coincide with the Obama Administration's push to create a Brain Activity Map Initiative, which will further advance the creation of a roadmap of human brain circuits.
The study was published in the journal Neuron.
The U.S. National Institute of Neurological Disorders and Stroke provides more information on the human brain.