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New scans show key brain interactions (7-19-99)

New brain images recorded in San Antonio reveal never-before-demonstrated "temporal dynamics" of the interactions of two important brain structures, the cerebellum and the basal ganglia. The structures imaged are implicated in a wide range of clinical disorders, including Parkinson's disease, autism, and the cognitive and motor effects of chronic alcoholism.

The findings, from the Research Imaging Center (RIC) at The University of Texas Health Science Center at San Antonio, are described in the Thursday, July 22, issue of Nature.

"The use of imaging to study the temporal dynamics of regional interactions in the brain is a field in its infancy," said Peter T. Fox, M.D., director of the RIC and corresponding author on the paper. "The present study is the first to demonstrate changes in regional processing demands and inter-regional interactions in the course of an ongoing behavior." The term "temporal dynamics" applies to changes over time during performance of a task.

The functional magnetic resonance (fMR) brain images were recorded as subjects held wooden shapes in both hands and distinguished between the two forms. Participants were asked to compare a series of different objects. The results demonstrated the cerebellum and basal ganglia working together as the subjects perceived the wooden shapes.

The paper, "Temporal Dissociation of Parallel Processing in the Human Subcortical Outputs," examines the interdependence of the cerebellum and basal ganglia in cognitive tasks, particularly sensory discrimination, said first author Yijun Liu, Ph.D., of the RIC and the Health Science Center's Department of Physiology. "The new images show that their interaction is involved in both sensory and motor activity," he said, "and at various points in performance of the assigned tasks."

In 1996 RIC scientists showed that the cerebellum, a large portion of the brain near the brain stem, is involved in perceptual, cognitive and motor activity related to the acquisition of sensory information. The basal ganglia, gray masses deep in the cerebral hemispheres and in the upper brain stem, long have been linked to motor functions.

But the relationship between the two was not strongly known. The Health Science Center scientists have contributed important new knowledge.

"The basal ganglia are strongly involved as discrimination of tactile objects begins, and the cerebellum more strongly as the task continues," Dr. Liu said.

"This is a new way of looking at imaging data which focuses on the time course of functional activations and interactions," Dr. Fox said. "Imaging temporal dynamics appears to be a promising route to a deeper understanding of clinical disorders of these brain structures."

The Nature article reflects work from Dr. Liu's completed doctoral dissertation. He received his Ph.D. in May. Co-authors from the Research Imaging Center are Jia-Hong Gao, Ph.D., fMR physicist and associate professor; Mario Liotti, M.D., Ph.D., assistant professor; Yonglin Pu, M.D., Ph.D., visiting assistant professor; and Peter Fox, M.D., director. Dr. Fox supervised Dr. Liu's Ph.D. studies and Dr. Gao was a dissertation committee member.

Any clinical application of the work is years away. "But this gives us future directions for using fMR to study brain function," Dr. Liu said.

Contact: Will Sansom