Dolphin Continuous Auditory Vigilance for Five Days

This report documents the first use of magnetic resonance images (MRIs) of living dolphins to register functional brain scans, allowing for the exploration of potential mechanisms of unihemispheric sleep. Diazepam has been shown to induce unihemispheric slow waves (USW), therefore we used functional...

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Bibliographic Details
Main Authors: Ridgway, Sam, Finneran, James, Carder, Don, Keough, Mandy, Van Bonn, William, Smith, Cynthia, Scadeng, Miriam, Dubowitz, David, Mattrey, Robert, Hoh, Carl
Format: Report
Language:English
Subjects:
Biology
BLOOD CIRCULATION
COMPARISON
DIAZEPAM
IMAGING TECHNIQUES
MAGNETIC RESONANCE IMAGING
MAMMALS
METABOLISM
PHYSIOLOGY
POSITRON EMISSION TOMOGRAPHY
SLOW WAVES
SPECT(SINGLE PHOTON EMISSION COMPUTED TOMOGRAPHY) SCANS
THESES
UNIHEMISPHERIC SLEEP
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Summary:This report documents the first use of magnetic resonance images (MRIs) of living dolphins to register functional brain scans, allowing for the exploration of potential mechanisms of unihemispheric sleep. Diazepam has been shown to induce unihemispheric slow waves (USW), therefore we used functional imaging of dolphins with and without diazepam to observe hemispheric differences in brain metabolism and blood flow. MRls were used to register functional brain scans with single photon emission computed tomography (SPECT) and positron emission tomography (PET) in trained dolphins. Scans using SPECT revealed unihemispheric blood flow reduction following diazepam doses greater than O.55mg kg- 1 for these 180-200 kg animals. Scans using PET revealed hemispheric differences in brain glucose consumption when scans with and without diazepam were compared. The findings suggest that unihemispheric reduction in blood flow and glucose metabolism in the hemisphere showing USW are important features of unihemispheric sleep. Functional scans may also help to elucidate the degree of hemispheric laterality of sensory and motor systems as well as in neurotransmitter or molecular mechanisms of unihemispheric sleep in delphinoid cetaceans. The findings also demonstrate the potential value of functional scans to explore other aspects of dolphin brain physiology as well as pathology. Published in the Jnl. of Experimental Biology, v209, p2902-2910, 2006.