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Scientists focus on a new hypothesis — of the cerebellum as a support structure that fine-tunes the brain's sensory input

San Antonio (July 14, 2003) — For a hundred and fifty years, prevailing wisdom has held that the cerebellum, a baseball-sized region of gray and white tissue sitting above the brain stem, is the control center for body movement. But recent studies, including some straight out of the laboratory, are suggesting the cerebellum is involved in a much wider set of behaviors and perceptions. Performance of the cerebellum might even help explain mysterious disorders such as autism.

These are some of the conclusions of neuroscientists James M. Bower, Ph.D., and Lawrence M. Parsons, Ph.D., both from The University of Texas Health Science Center at San Antonio (UTHSC). They are the authors of a feature article to appear in the August 2003 issue of Scientific American, which hits newsstands July 22. One of their recent studies, which used functional magnetic resonance imaging (fMRI) to compare cerebellar activity as human subjects completed simple vs. more complex sensory tasks, is highlighted in the article. The study was conducted at UTHSC's highly regarded Research Imaging Center.

Recent results "suggest a need to substantially revise current thinking about the function of this organ," Drs. Bower and Parsons write. "The cerebellum has once again become an area of 'tantalizing mystery.'" Studies of the sense of touch have shown that the cerebellums of different animals (rats, monkeys and cats) receive input from different parts of the body — cats from their forepaws, monkeys from their fingers and rats from their mouths. The rat cerebellum even responds differently as different areas in or near the mouth are touched.

Drs. Bower and Parsons, collaborating with Peter T. Fox, M.D., at the Research Imaging Center, conducted a study comparing "passive sensing" vs. "active sensory comparison." They used fMRI to record the activity of the cerebellums of six human subjects. In the first part of the experiment, fine and coarse sandpapers were rubbed across the individuals' fingertips, resulting in little cerebellar activity. In the second test, individuals were asked to compare the feel of the two papers. Cerebellar activity increased.

In a third test, the subjects were asked to pick up and drop small wooden balls in a bag. The balls varied in shape and feel. Little cerebellar activity occurred. In the final test, the individuals were asked to grade the different shapes and textures of the balls as they felt them. Cerebellar activity increased. Drs. Bower and Parsons said these results, first published in the journal Science, "support our hypothesis that the cerebellum is more involved in sensory than pure motor function."

They furthermore assert that the cerebellum is a support structure for the brain. Some individuals have survived total removal of the cerebellum and regained considerable normal function. The hypothesis advanced by Drs. Bower and Parsons makes room for this phenomenon, suggesting that the cerebellum is not the sole command center for any "particular overt behavior or psychological process," but supports the brain by "monitoring incoming sensory data and making continuous, very fine adjustments in how that information is acquired."

Dr. Bower is professor of computational neurobiology at the Research Imaging Center and Dr. Parsons is professor of cognitive neuroscience. Dr. Bower also is a professor at the Cajal Neuroscience Center at The University of Texas at San Antonio. Dr. Fox is professor of radiology, medicine, psychiatry and physiology at the Health Science Center and director of the Research Imaging Center.

Contact: Will Sansom or Lucie Portela