Functional MRI of the olfactory system in conscious dogs

PLoS One. 2014 Jan 23;9(1):e86362. doi: 10.1371/journal.pone.0086362. eCollection 2014.

Abstract

We depend upon the olfactory abilities of dogs for critical tasks such as detecting bombs, landmines, other hazardous chemicals and illicit substances. Hence, a mechanistic understanding of the olfactory system in dogs is of great scientific interest. Previous studies explored this aspect at the cellular and behavior levels; however, the cognitive-level neural substrates linking them have never been explored. This is critical given the fact that behavior is driven by filtered sensory representations in higher order cognitive areas rather than the raw odor maps of the olfactory bulb. Since sedated dogs cannot sniff, we investigated this using functional magnetic resonance imaging of conscious dogs. We addressed the technical challenges of head motion using a two pronged strategy of behavioral training to keep dogs' head as still as possible and a single camera optical head motion tracking system to account for residual jerky movements. We built a custom computer-controlled odorant delivery system which was synchronized with image acquisition, allowing the investigation of brain regions activated by odors. The olfactory bulb and piriform lobes were commonly activated in both awake and anesthetized dogs, while the frontal cortex was activated mainly in conscious dogs. Comparison of responses to low and high odor intensity showed differences in either the strength or spatial extent of activation in the olfactory bulb, piriform lobes, cerebellum, and frontal cortex. Our results demonstrate the viability of the proposed method for functional imaging of the olfactory system in conscious dogs. This could potentially open up a new field of research in detector dog technology.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

  • Animals
  • Brain Mapping
  • Consciousness
  • Dogs / physiology*
  • Frontal Lobe / physiology*
  • Magnetic Resonance Imaging
  • Olfactory Bulb / physiology*
  • Olfactory Pathways
  • Olfactory Perception*

Grants and funding

The authors acknowledge financial support for this work from Auburn University Intramural Level-3 research grant from the Office of the Vice President for Research, Auburn University. This work was also supported by The Defense Advanced Research Projects Agency (government contract/grant number W911QX-13-C-0123). The views, opinions, and/or findings contained in this article are those of the authors and should not be interpreted as representing the official views or policies, either expressed or implied, of the Defense Advanced Research Projects Agency, Department of Defense or the United States Government. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.