Thursday, September 04, 2014

Scientists Switch "Good" and "Bad" Memories in Mice

"Recording a memory is not like playing a tape recorder, it's a creative process," Susumu Tonegawa, director of the RIKEN-MIT Center for Neural Circuit Genetics at MIT and senior author of the paper, said in a Nature news conference...The researchers used genetically engineered mice who expressed a light-sensitive protein, allowing the scientists to activate different neurons by targeting them with a laser. They exposed half of them to a positive stimuli (interaction with a female mouse) and half to a negative one (small electric shocks). This activated both the neurons that form the structure of a memory, which are found in the hippocampus, and the neurons that determine the emotional value of a memory, in the amygdala. Then the mice were placed in a box with two sides that the mice could move freely between. When the mice moved to one particular end of the box, a light would shine down on them — activating the neurons that had been active during their conditioning. So for the mice who'd been shocked, the "target" end of the box meant an activation of the fearful memory. For the mice who'd spent time with a female, the same target end meant and activation of the pleasurable memory. Sure enough, the shocked mice avoided the target, while the others spent more time there than the side without a laser light. more

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