By stimulating different areas of the brain with electrical shock, Wilder Penfield, a neurosurgeon in the 1940s, found his patients could recall random information “ like the smell of cookies. Since then, two studies have now found evidence to support the memory storage theory that Penfield stumbled across. The studies have even found that, in mice, it is possible to manipulate brain cells in order to produce false memories.
Researchers from Scripps Research Institute in San Diego, California, genetically altered mice in their study so that neurons once fired would fire again when the brain was injected with a drug.
The team, led by Mark Mayford, took each mouse and put them into a box exposed to a color and smell, which allowed the neurons in the brain to form a memory of the experience. Because these neurons were fired when making the memory, they could be re-fired when the drug was injected. This allowed the researchers to induce involuntary memory of the experience in the mouse.
Each mouse was then placed into a second box, with different colours and smells. They injected the drug, which made the mice recall the first box experience, and then gave them a slight electrical shock.
Under normal circumstances, the shock would instill fear in its current box, but in this case when the mouse was shocked it did not. It was thinking about the experience it had in the first box. Eventually, they got the memories of each box intertwined and thus developed a fear of both boxes. The only time the mouse would panic was when it was in the second box and the drug was injected.
Mayford says this “hybrid” false memory suggests that two different groups of neurons encode each memory and do not interfere with one another.
“It sounds like something my mother would say: if you want to remember something, go to the place you learned it,” says Sheena Josselyn of The Hospital for Sick Children in Toronto, Ontario, Canada. “The fact that you can introduce new bits of information into memory opens up a whole new universe of research.”
Susumu Tonegawa of the Massachusetts Institute of Technology offered a different way to create false memories. His team genetically engineered mice so that when they formed a memory of a box, the neurons involved became responsive to light. As the mouse was forming the memory they were given an electrical shock, then put in a different box and shown pulses of light through optic fibers implanted in the mouse’s brain. This activated the neurons that were associated with that memory and the mouse froze, terrified in its tracks.
The researchers were able to determine that the active neurons, in 2% of the cells, were located in a specific area of the brain’s memory center, the hippocampus. Based on their experience, Tonegawa says the methods could be used to bring out different types of complex behavior. They are looking at how parts of the brain past the memory center connects to make the mouse freeze. According to him, “This is the “ultimate experiment” for showing that memories are kept in discrete areas of the brain.”
About the author:
Ron White is a two-time U.S.A. Memory Champion and memory training expert. As a memory keynote speaker he travels the world to speak before large groups or small company seminars, demonstrating his memory skills and teaching others how to improve their memory, and how important a good memory is in all phases of your life. His CDs and memory products are also available online at BrainAthlete.com.
Sources:
NewScientist “ False Memories Generated in Lab Mice: http://www.newscientist.com/article/dn21621-false-memories-generated-in-lab-mice.html
