The scientists administered electric shocks to the snails' tails. Following this training, when the scientists gently touched a snail's siphon (an organ in their mid-section used in respiration), the animal responded with a reflexive contraction that lasted about 50 seconds. A week later, when the scientists touched the siphon, the reflex still lasted 30 seconds or more, rather than just the second or two the reflex normally lasts without the shock training. This constituted a long-term memory.
Then, once the marine snail had formed the long-term memory, the scientists injected an inhibitor of PKM into the snail and 24 hours later touched the siphon; the marine snail responded as though it had never received the tail shocks, with a very brief contraction.
"The long-term memory is gone," Glanzman said.
Life scientists agree that learning is due to changes in the synaptic connections, some of which strengthen and some of which weaken, in the brain. This new research opens the door to learning how the changes in synaptic connections are maintained and what role PKM plays in this memory maintenance. Glanzman and his colleagues are now conducting detailed analyses.
During the long-term memory, new synaptic connections grow between the sensory neuron and the motor neuron. If the scientists inhibit PKM, will those synaptic connections disappear?
"We're going to study that," Glanzman said. "Now we can study the cell biology of how PKM maintains long-term memory. Once we know that, we may be able to alter long-term memories. This has implications for psychiatric disorders that are related to memory. Post-traumatic stress disorder is a hyper-induction of a long-term memory that won't go away."
|Contact: Stuart Wolpert|
University of California - Los Angeles