DURHAM, N.C., July 29 -- Neurobiologists at Duke University Medical Center have captured the first detailed images of a living brain in the act of recognizing specific odor molecules. As reported in Neuron, the researchers refined an imaging technique used to visualize brain activity by increasing its resolution tenfold to detect changes in the tiny hair-thin olfactory structures, called glomeruli, in rats' brains.
The objective was to visually detect a particular odorant triggering the activity of a specific glomerulus, one of the tiny basket-like structures covering the surface of the olfactory bulb. Earlier research has shown that each one of the 2,000 glomeruli receives impulses from nasal receptors tuned to specific odorants and relays those signals to higher processing centers in the brain.
The scientists' method of detection relied on the fact that active cells consume more oxygen, converting oxygen-carrying oxyhemoglobin to deoxyhemoglobin. Since deoxyhemoglobin absorbs more red light than the oxygenated form, the scientists could identify activated glomeruli by imaging the olfactory bulbs under a red light.