Researchers from the University of Texas at Austin have shown that when electric fish zap each other in dark waters, their neurons store a memory of the sizzling communiqué by turning on special cell membrane channels.

The channels give the fish neurons the ability to retain a memory long after its original stimulus is gone. "There is short-term stimulation that results in long-term changes in excitability," says Dr. Harold Zakon, professor of neurobiology. "Essentially, it is memory."

The electric fish discharge electrical signals to survey their environment and communicate with each other. "Every time they discharge, it's kind of like they are opening their eyes and closing them," says Zakon. "Each pulse of electricity is a snapshot of the environment. These guys are swimming around and discharging at a very regular frequency. They're digitising their environment."

But a problem occurs when the fish are close to each other. They can jam each other's electrical signals. In response, one of the fish will jump to a higher frequency to avoid the jamming signal. The scientists found that once the jamming avoidance has started, the fish's neurons continue to discharge at a higher frequency, even after its neighbour fish may have swum away.

The researchers discovered that the neurons' memory was not caused by increased flow of glutamate to their synapses. Instead, the glutamate sets off a cascade of events in the neuron that results in the activation of ion channels, called TRP channels, which then remain active for a long time.

"The long-term activation of these TRP channels," says Zakon, "is the 'memory.'" The researchers don't yet understand how the stimulus leads to the long-lasting activation of the TRP channel. They are pursuing further studies.; Source: Universtiy of Texas at Austin