Analysis of the brains of the euthanized rats revealed decreased levels of Fos, a protein marker of neuronal activity, in the amygdala region of the brain while the olfactory signals appeared to block fear responses.

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In 1986 Kevin Kinsella, a venture capitalist, spotted a neuroscience paper about the olfactory cortex of a rat's brain.

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After cracking the code, Buck set out to trace the way connections extend from the olfactory bulb into the olfactory cortex, the part of the brain that processes odor signals.

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In the study, funded by the Medical Research Council and published in the neurology journal Brain, the dogs had olfactory ensheathing cells from the lining of their nose removed.

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Decreased Fos in the amygdala, the brain's emotional processing center, suggests the olfactory signals suppressed amygdala activation, and possibly fear, researchers said.

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Each neuron has a long fiber, or axon, that stretches upward through a tiny opening in the bone above it and into the olfactory bulb, a plum-size mass in the front of the brain, behind the forehead.

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With time, neuroscience research uncovered two parts of the brain that evidence neurogenesis: the hippocampus, associated with memory formation, and the olfactory bulb, associated with the sense of smell.

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