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Making Scents

It was easy to envision from the outset how the MEMS research related to Lucent’s business goals. But other Physical Research Lab work has a more tangential relation to the bottom line and may take many years to pay off. Take Alan Gelperin, proprietor of the Slug Emporium, a bank of refrigerators crammed with the slithery beings. A 17-year lab veteran, Gelperin is a computational neurobiologist and neuroethologist, meaning he studies the algorithms nerve cells use to produce behavior. He concentrates on slugs-snails without shells-because the creatures possess an intriguing ability to rapidly and reliably learn about odors, and because this “learning” continues even after their brains have been removed from the body for experimentation.

Gelperin works primarily with Limax maximus, the spotted garden slug. The key to devising models that can be simulated in software or even wired into a machine lies in physiological experiments designed to get at how slugs store and access their odor memories, then take action based on their experience with certain scents. In collaboration with colleague Winfried Denk, Gelperin studies dyed slug neurons through two-photon scanning, a microscopy technique that allows him an unprecedented view of the activity inside the processes of single nerve cells.

Similarly, by applying dyes that change their fluorescence if the voltage across the cell membrane changes, he and researcher David Tank, head of the Biological Computation Research Department, have detected electrical waves and oscillations that originate at one end of the odor-analyzer circuit called the procerebral lobe and propagate along it-starting over again as the previous signal dies out. One hypothesis is that the wave acts as a kind of time stamp for storing data. That is, with the detection of an odor and an associated stimulus-a shock, for instance-the memory of that odor is stored in a specific band of cells that run perpendicular to the wave. “Where the wave is determines where the memory storage is going to happen,” Gelperin suggests. The next time the slug is exposed to the odor, it accesses the cells at the same point along the wave-and orders an appropriate response, like gliding away from an odor previously paired with shock. Many experiments remain to be performed before this hypothesis can be confirmed-and possibly incorporated into tomorrow’s neural networks.

But long-range studies are not the only thing Gelperin does. Working with AT&T’s NCR unit before it spun off as a separate company under trivestiture, he used his expertise in neural networks to develop an electronic nose for automated checkout machines. Electronic checkers have little trouble reading bar codes, but they run into real trouble trying to tell a banana from an orange. Gelperin worked with Bell Labs researcher Sebastian Seung, a neural network and machine learning theorist, to create a system that emits a vacuum pulse to pull odors over special sensors that can tell broccoli from lettuce. Last November, Gelperin received a patent on the device.

Gelperin delights in being able to apply his knowledge of neurobiology to solve real-world problems. But he acknowledges that not everybody at the labs has accepted the need to apply their scientific findings. “Some folks just didn’t want to think that way,” he says. “They had their pure science, and pure was with a capital P.’ And they just didn’t want to be bothered.”

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