Human brain 'blurs fast-moving images'
The brain sees fast-moving objects by using blurs or streaks, as seen in photographs, researchers say.
"The brain doesn't see instantaneously. It takes about 100 milliseconds for the neurones in the brain to fully encode information," ABC Science quoted Professor David Alais, a co-author of the paper from the University of Sydney, a saying.
"If you move things really fast it will blur - exactly like a blurred camera image," he said.
Traditionally, scientists would have considered this "smeared image" to have been a problem for the brain to contend with but in 1999 a researcher by the name of Wilson Geisler proposed that this blurring could be useful in the brain's processing of fast-moving images.
His idea was that since the smearing would always be in the direction the object is moving, it might help you see accurately which way it's going, Alais said.
Scientists have traditionally believed that the brain perceives form (static objects) and motion using two separate neuronal pathways, but Geisler argued that form-sensitive neurones, not usually involved in detecting motion, could pick up the orientation of a static motion streak.
According to Geisler, this process kicks into action when an object moves above a critical speed - defined as twice its width over 100 milliseconds, says co-author Dr Deborah Apthorp of the University of Wollongong's school of psychology.
Apthorp used functional MRI scans to look for evidence to support Geisler's ideas, as part of her PhD, under Alais' supervision.
Apthorp says evidence from previous behavioural experiments in humans have supported Geisler's theory, but there has never been any direct evidence from the human brain.
"We wanted to put people in the scanner and see if we got a similar result," she said.
Apthorp placed people in a fMRI scanner and measured their brain activity as they were shown a number of stimuli.
The study participants were shown fast moving images moving upwards to the left or the right, and slow moving images moving up to the left or right. They were also shown static images tilted to the left or the right.
The researchers found that when the images were moving fast enough to produce a motion streak, the pattern of brain activity across the early visual cortex (the part of the brain involved in basic visual processing) was similar to that when people were viewing static images with the same orientation.
When the motion was too slow to form streaks, the brain showed a different pattern of activity.
"This suggests motion streaks are measurable in the brain," Apthorp said.
"It is direct evidence from the human brain to support Geisler's model and shows motion and form pathways are not as separate as people think," Apthorp added.
The study has been recently published in the Proceedings of the Royal Society B.