Functional imaging of dolphin brain metabolism and blood flow

Sam Ridgway, Dorian Houser, James Finneran, Don Carder, Mandy Keogh, William Van Bonn, Cynthia Smith, Miriam Scadeng, David Dubowitz, Robert Mattrey, Carl Hoh

Research output: Contribution to journalArticlepeer-review

55 Scopus citations


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. MRIs 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 0.55 mg 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.

Original languageEnglish (US)
Pages (from-to)2902-2910
Number of pages9
JournalJournal of Experimental Biology
Issue number15
StatePublished - Aug 2006


  • Brain
  • Diazepam
  • Dolphin
  • Functional imaging
  • Hemisphere autonomy
  • MRI scan
  • PET scan
  • SPECT scan
  • Slow wave
  • Tursiops
  • Unihemispheric sleep

ASJC Scopus subject areas

  • Ecology, Evolution, Behavior and Systematics
  • Physiology
  • Aquatic Science
  • Animal Science and Zoology
  • Molecular Biology
  • Insect Science


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