SYDNEY, Feb. 3 (Xinhua) -- Researchers from the University of Queensland (UQ) have revealed the process of how the human brain adapts to external stimulation, which could provide clues for further research into what happens when the brain is damaged.
The research, published in Proceedings of the National Academy of Sciences journal recently, discovered that two distinct processes are triggered in the human brain when exposed to prolonged or repeated sensory inputs.
"When light enters the eye, neurons in visual areas of the brain begin to fire and scientists have long debated whether the brain adapts to this prolonged input because the neurons get fatigued, or instead fire more selectively to sharpen perception," said Reuben Rideaux, lead author and researcher from the university's Queensland Brain Institute (QBI).
"Our work has shown for the first time that both processes occur, but they become active at different points in time," said Rideaux.
The research team designed an experiment to measure a phenomenon called the "tilt-aftereffect", a visual illusion in which prolonged exposure to a visual stimulus causes shifts in subsequently perceived orientations.
"If you stare for a few seconds at a patch of black and white stripes rotated slightly clockwise from vertical, and then look at a perfectly vertical pattern, those vertical stripes will appear to be tilted slightly counterclockwise," Rideaux explained.
Human observers were invited to look at some of the patterns, while their whole-brain activities were also recorded before and after they adapted to visual grating stimuli.
Rideaux noted that they found visual neurons from observers initially show fatigue during the adaptation phase, but after a few hundred milliseconds, they are sharpening perception.
Jason Mattingley, co-author and professor from the QBI, said the process could be compared to completing a jigsaw puzzle, as people normally generate ideas of what the puzzle should look like when it's complete but will pay more attention to the fine details of each piece later.
"Having a better understanding of how sensory systems work in a healthy brain can tell people more about what happens when the system malfunctions, paving the way to better diagnosis and treatment of sensory impairments in the future," said Mattingley. ■
