DURHAM, N.C. -- Using a high-resolution video technique on laboratory rats, neurobiologists at Duke University Medical Center have captured the first detailed images of the living brain in the act of recognizing specific odor molecules. The scientists say their achievement will open the way to deciphering the brain's internal "language" of smell.
More broadly, say the researchers, the imaging technique can give them new insights into the machinery of learning, as they explore how training alters the odor-recognition process.
The researchers -- graduate student Benjamin Rubin and Howard Hughes Medical Institute Investigator Lawrence Katz -- reported their achievement in the July issue of Neuron. To record odor-recognition, the researchers refined an imaging technique used to visualize brain activity in other parts of the brain. They increased its resolution tenfold to detect changes in the tiny hair-thin olfactory structures, called glomeruli, in rats' brains.
They began their studies by thinning out a section of a rat's skull until they could see the olfactory bulbs -- stem-like projections in the forebrain that receive signals from the chemical receptor cells that line the nasal passages.
Rubin's and Katz's objective was to visually detect when a specific odorant triggered the activity of a specific glomerulus -- tiny basketlike structures covering the surfaces of the olfactory bulb. These glomeruli, each about the diameter of a human hair, are the basic units of olfactory reception. Previous research has shown that each of the 2,000 glomeruli in the olfactory bulbs receives impulses from nasal receptors tuned to specific odorants, relaying those signals to higher processing centers in the brain.
The scientists' detection method depended on the fact that active cells
consume more oxygen, converting oxygen-carrying oxyhemoglobin to
deoxyhemoglobin. Since deoxyhemoglobin absorbs red light more
Contact: Monte Basgall