"This means that once PKM is formed, there is no way to shut it off," said Glanzman, who is a member of UCLA's Brain Research Institute. "Once it is activated, PKM's continual activity maintains a memory until PKM degrades."
Glanzman decided to study PKM in the marine snail, which has simple forms of learning and a simple nervous system, so that he could understand in precise detail how PKM's activity maintains a long-term memory, a process that is not well understood.
Glanzman and his colleagues researchers Diancai Cai, lead author of the study; Kaycey Pearce; and Shanping Chen, all of whom work in his laboratory studied a simple kind of memory called sensitization. If marine snails are attacked by a predator, the attack heightens their sensitivity to environmental stimuli a "fundamental form of learning that is necessary for survival and is very robust in the marine snail," Glanzman said.
"The advantage of Aplysia," he said, "is that we know the neurons that produce this reflex; we know where they are in the nervous system."
The scientists removed the key neurons from the snail's nervous system and put them in a Petri dish, thereby recreating in the dish the two-neuron "circuit" a sensory neuron and a motor neuron that produces the reflex.
"The point is to reduce the problem so we can study on a fundamental biological level how PKM is maintaining long-term memory," Glanzman said.
They succeeded in erasing a long-term memory, both in the snail itself and in the circuit in the dish. They are the first scientists to show that long-term memory can be erased at a connection between just two neurons.
"We found that if we inhibit PKM in the marine
|Contact: Stuart Wolpert|
University of California - Los Angeles