By Davide Castelvecchi
From Science News, April 21st, 2007; Vol.171 #16 (p. 253)
Memories form when networks of neurons learn to fire in new patterns. Biophysicists have now put that assumption to the test by inducing synchronized firings in neurons sitting on a chip.
Itay Baruchi and Eshel Ben-Jacob, two biophysicists at Tel Aviv University in Israel, extracted neurons from rat embryos and grew the nerve cells on a chip equipped with 64 electrodes to detect neuron activity. Repeatedly dropping tiny amounts of nerve-stimulating chemicals at a chosen spot, the researchers saw the same cascade of firings each time the neurons relayed signals to their neighbors. Eventually, the neurons began firing in that pattern without the chemical stimulation. The neurons had formed a memory, the researchers say.
Applying chemicals to different spots created additional memories without erasing those already formed. That contrasts with previous experiments using electrical stimuli, where new memories tended to erase old ones, Ben-Jacob says. His team’s report appears in the May Physical Review E.
Stefano Vassanelli of the University of Padua in Italy says that he’d like to combine Ben-Jacob’s chemical-stimulation method with his own team’s neuron chips, which can simultaneously detect thousands of firings through silicon transistors.