Smells that are similar to each other evoke similar activity pattern in the brain, reports a functional imaging study published online this week in Nature Neuroscience.
Jay Gottfried and colleagues used fMRI to track changes in brain activity in the posterior piriform cortex as people sniffed various odors. They found that when patterns of activity in the posterior piriform cortex were similar, people were more likely to indicate that the odors they were sniffing smelt similar. This was not simply due to the chemical structure of the molecules making up the odors, as odors with very different chemical structures were rated as smelling similar.
This overlap between brain activation and perception was not found in other areas of the brain previously linked to processing smells. This study suggests that the posterior piriform cortex is likely to be critical for categorizing scents.