Cerebellum Plays More Complex Role, Study Says
A middle-aged man who has his head in a magnetic brain scanner while a researcher rubs the man’s fingers with sandpaper might not look like the makings of a minor revolution. But that experiment has led scientists from Caltech and the University of Texas to a new understanding of the function of the cerebellum, the wrinkled, lime-sized cluster of gray and white matter nestled beneath the cortex.
In a study published today in the journal Science, the researchers strongly suggest that the cerebellum is not just involved in guiding bodily movements, as scientists have believed for a century and generations of grade-school biology students have been taught. Instead, say the researchers, the cerebellum, long regarded as something of a neurological drone, actually has a much higher security clearance, being directly involved in processing a variety of sensory information, such as the feel of things.
According to this revisionist theory, the cerebellum does not merely help you reach for your car keys (the classic understanding of its function), it also helps you tell the difference between your car key and your house key with your eyes closed.
“Very important,” Enrico Mugnaini, director of the neuroscience institute at Northwestern University, said of the study, adding that it sheds “new light” on the brain structure. The research, he said, gives the cerebellum something of a promotion, involving it in tasks “generally assumed to be higher cortical functions.”
James Bower, a neurobiologist at Caltech, instigated the study, which he conducted with five collaborators at the University of Texas Health Science Center.
Bower said that when he presented preliminary findings on the cerebellum’s elevated role at a European neuroscience meeting last year, audience members gasped. They “thought it was sort of loony,” he said.
Any deep inroad into the brain excites pure scientists who labor in this most mysterious of all matter. Bower also imagines that the work, if borne out by other experiments, may lead to a better understanding of neurological and cognitive disorders. “I think there’s a fair chance that some forms of autism may very well involve the cerebellum,” he said.
“It’s not every day that you get to overturn 150 years of hard, rigorous observation about a brain structure as big as the cerebellum,” said Lawrence Parsons, a cognitive scientist on the Texas research team. After all, he said, “the cerebellum is a big piece of meat.”
The conventional view of the cerebellum grew largely out of decades of medical reports describing people with brain injuries and lab studies in which researchers selectively damaged animal brains. Damage to the cerebellum caused movement disorders--jerky steps or an inability to guide an outreached hand to a desired spot.
The ingenuity of the new study, researchers say, was its ability to distinguish the structure’s motor and sensory functions. The researchers tested five men and one woman, having each lie down in a magnetic resonance imaging machine. The MRI measured nerve activity in a part of the cerebellum while the subjects were put to several tests, including touching or grasping different objects.
Contrary to the old thinking, activity in the cerebellum rose distinctly when sandpaper was rubbed on their fingers while their hand was strapped to the table. That in itself showed that the cerebellum was not concerned only with motion but with processing tactile sensation, Bower said. And finger movements alone, he said, did not trigger as much cerebellum activity as when the subjects compared the feel of different objects.
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Rethinking the Brain
Scientists have overturned basic ideas about how the cerebellum works, suggesting that it coordinates a range of sensory information instead of just movement.
Cerebral Cortex
Skull
Midbrain
Pituitary gland
Cerebellum
Medulla
Spinal nerves
