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TECHNOLOGY, COMPUTING, AND SIMULATION

Bispectral Index Monitoring of Unihemispheric Effects in Dolphins

Red S. Howard, MD, PhD^*, James J. Finneran, PhD, and Sam H. Ridgway, DVM, PhD

From the *Department of Anesthesiology, Naval Medical Center; United States Navy Marine Mammal Program, SPAWARSYSCEN, San Diego, California; Department of Pathology, School of Medicine, University of California, La Jolla, California.

Address correspondence and reprint requests to Red Howard, MD, Department of Anesthesiology, Naval Medical Center, 34800 Bob Wilson Drive, San Diego, CA 92134-5000. Address e-mail to rhoward{at}ucsd.edu.

When dolphins sleep, their electroencephalographic activity may change in only one cerebral hemisphere; i.e., the left and right brain hemispheres can take turns sleeping. We demonstrate that the bispectral index (BIS) monitor can detect interhemispheric asymmetry in the dolphin species Tursiops truncatus. Using two BIS sensors placed simultaneously over each side of the dolphin’s head, we often, but not always, found significant differences between the two BIS values (e.g., left side 60 and right side 90) in non-medicated animals and in animals given propofol, atropine, and/or diazepam. Observations were each made over a period of approximately 3 h on dolphins resting out of the water. Unihemispheric effects may be inducible pharmacologically in dolphins. The dolphin, with its human-sized brain, may provide an animal model for study of unihemispheric effects in humans.

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