Dissociable codes of odor quality and odorant structure in human piriform cortex

Neuron. 2006 Feb 2;49(3):467-79. doi: 10.1016/j.neuron.2006.01.007.


The relationship between odorant structure and odor quality has been a focus of olfactory research for 100 years, although no systematic correlations are yet apparent. Animal studies suggest that topographical representations of odorant structure in olfactory bulb form the perceptual basis of odor quality. Whether central olfactory regions are similarly organized is unclear. Using an olfactory version of fMRI cross-adaptation, we measured neural responses in primary olfactory (piriform) cortex as subjects smelled pairs of odorants systematically differing in quality and molecular functional group (as one critical attribute of odorant structure). Our results indicate a double dissociation in piriform cortex, whereby posterior regions encode quality (but not structure) and anterior regions encode structure (but not quality). The presence of structure-based codes suggests fidelity of sensory information arising from olfactory bulb. In turn, quality-based codes are independent of any simple structural configuration, implying that synthetic mechanisms may underlie our experience of smell.

Publication types

  • Comparative Study
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adult
  • Brain Mapping*
  • Cerebral Cortex / blood supply
  • Cerebral Cortex / physiology*
  • Discrimination, Psychological / physiology
  • Female
  • Humans
  • Image Processing, Computer-Assisted / methods
  • Magnetic Resonance Imaging / methods
  • Male
  • Models, Biological
  • Odorants*
  • Olfactory Pathways / blood supply
  • Olfactory Pathways / physiology*
  • Oxygen / blood
  • Reaction Time / physiology
  • Smell / physiology*
  • Time Factors


  • Oxygen