Thursday, October 23, 2008

Erasing Memory

"What is your name?"

[...] Norman Kent's name leaped into his mind, in response to the question - and vanished.

It was not simply the name itself tha t vanished. with it went eh associations and mnemonics keyed to it in his memory. Jokes from childhood about Superman, jokes from adolescence about the Norman Conquest, jokes from he jungle about the Norman DeINvastion. An old Simon Templar novel he had read many eyars ago, and remembered all his life because it featured a hero named Nroaml Kent, who laid down his life for his friends. Certain times when the speaking of his name had been a memorable event. The sight of his dogtags. The nameplate on the desk in his office at the University. His face in the mirror.

If you take a hologram of the word "love" and try to read a page of print through it, you will see only a blur. But if the word "love" is printed anywhere on that page, in any typeface, you will see a very bright light at that spot on the page. In much the same way, one of the finest computers in the world riffled through the "pages" of Norman Kent's memory, scanning holographs with a reference standard consisting of the sound of his name. Each one that responded strongly was taken from him.

All this took place at computer speed. Without perceptible hesitation the man on the table answered honestly and happily, a puppy fetching a stick. "I don't know."
~ Mindkiller, Spider Robinson
The ability to erase specific memories is an old one in science fiction. While not the first to use it as a plot device, Robinson's 1982 novel Mindkiller goes into detail about how the erasure of something as simple as a name from the mind requires the removal of many different associated memories. And unlike the characters in Eternal Sunshine Of The Spotless Mind, the man who is given the treatment is well-aware of the holes in his memory.

In this week's issue of Neuron, scientists at the Shanghai Institute of Brain Functional Genomics and the Brain and Behavior Discovery Institute at the Medical College of Georgia in Augusta reported the first step in developing such technology: they successfully erased specific fearful memories in mice while those memories were being retreived. The specific method the neuroscientists used won't be easily transferred to humans because it involved specially constructed transgenic mice that allow induction ofexpression of high levels of an enzyme involved in the memory process (CaMKII) while the memory to be erased was being recalled. Even so, the study's principal investigator, Joe Z. Tsien, has speculated about the method's usefulness to treat people suffering from traumatic memories:
"While memories are great teachers and obviously crucial for survival and adaptation, selectively removing incapacitating memories, such as traumatic war memories or an unwanted fear, could help many people live better lives," Tsien said.
It's not clear, however, whether even selective removal of such memories would leave the patient with the feeling that some important part of them was missing.

Original article: Cao X, et al. "Inducible and Selective Erasure of memories in the Mouse Brain via Chemical-Genetic Manipulation" Neuron 60(2): 353-366 (2008) doi:10.1016/j.neuron.2008.08.027


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