Researchers were able to transfer the memories of a sea slug scared of being shocked to another sea slug. They were able to do this by transplanting the genetic material of the original sea slug to the other via an injection.
This transfer was able to change the behavior of the sea slugs.
Researchers from the University of California, Los Angeles gave sea slugs a slight electric shock by implanting wires into the tails of California sea hares. This caused them to become scared of being touched, they would contract their gills into a defensive action. After the shocks, scientists took RNA from the slugs that were shocked and injected it into slugs that hadn't been shocked.
Those slugs then changed their behavior, they were more receptive to touch by contracting their siphons for a longer period than those who didn't have the genetic material injected. Siphons are tube-like structures in molluscs in which water flows. This was repeated with sea slugs that had been hooked up to wires but not shocked and it didn't work.
Researchers say that his experiment shows how essential parts of the memory trace or engram can be. This behavior was held in RNA instead of in the connectivity of brain cells. The memory of being shocked was very specific to the sea slug, researchers believe that they found evidence that epigenetic changes were storing memories of the shocks.
Lead author of the study David Glanzman said to the BBC that this can change the way scientists think memories are stored. He said that if the memories were held in the synapses that the experiment would not have been able to work.
During the experiment, researchers noted that neurons in a petri dish fired more if they received the genetic material of the shocked slugs than the material from the unshocked slugs. The team published their paper in eNeuro.
Changing Minds About Memory
Dr. Todd Sacktor, a neurologist from SUNY Downstate Medical Center told Scientific American that this memory transfer was shocking. He says that researchers are still trying to work out the way of how memories are stored.
Li-Huei Tsai, a neuroscientist, and director of the Picower Institute for Learning and Memory at the Massachusetts Institute of Technology says that this idea could challenge the filed but that it is only part of the concept that epigenetic mechanisms play a role in the formation of memories.
Other scientists are dubious about the work. Tomas Ryan of Trinity College Dublin. He told the Guardian that the work is interesting but that he doesn't think that the team transferred a memory. He thinks that a behavioral response was triggered in the slugs when the genetic material was transferred.
How Are Memories Stored?
The brain stores memories in two ways. Short term memories are stored in the pre-fontal lobe. Short-term recollection is translated into long-term memory in the hippocampus, an area that is deeper in the brain. The hippocampus is able to string various simultaneous memories into a single memory. Connections between neurons associated with a memory eventually become a fixed combination so that memories are tied with certain events such as a piece of music.
Even though some sort of memory was transferred between the sea slug it is not as complex as a human. The sea slugs used in the experiments have a much simple brain with only 10,000 neurons compared to the human brain that contains around 100 billion.