Researchers get partial memory control and create "hybrid" memories in mice
By Darren Quick
March 22, 2012
You may remember – pun intended – that earlier in the week we reported on research that may provide an explanation of how memories are stored in the brain. In related news, a team consisting of researchers from the Scripps Research Institute, the University of Oregon and the University of North Carolina has found a way to partially control a specific memory in mice by turning neurons in their brains on and off. Although the research is in its early stages, the scientists say it could lead to a better understanding of how memories form and maybe even provide ways to change people’s thought patterns.
Knowing that stimulating various regions of the brain can trigger behaviors and memories, the researchers set out to manipulate specific memories by inserting two genes into mice. One of the genes produces receptors that the researchers could chemically trigger to activate a neuron. This gene was tied to a natural gene that turns on only in active neurons, such as those involved in the formation or recall of a particular memory. Put simply, the researchers installed on-off switches on neurons involved in the formation of specific memories.
The team’s main experiment saw the “on” switch triggered in neurons that were active as mice learned about a new environment – dubbed Box A – that had distinct colors, smells and textures. The mice were then given a chemical that would activate the neurons associated with the memories formed of Box A and placed in a second distinct environment – Box B.
When the chemical switch was turned on while they were in Box B, the mice showed signs of recognition, indicating that they were forming a kind of hybrid memory that combined their external observations (Box B) with their internal thoughts (Box A). Neither being in Box B without the chemical switch activated nor activating the switch outside of Box B produced memory recall by the mice.
“We know from studies in both animals and humans that memories are not formed in isolation but are built up over years incorporating previously learned information,” said Scripps Research neuroscientist Mark Mayford, who led the study. “This study suggests that one way the brain performs this feat is to use the activity pattern of nerve cells from old memories and merge this with the activity produced during a new learning session.”
The team is now working towards more precise control that will allow them to turn a specific memory on or off at will, so that a mouse will perceive itself to be in Box A, when it is in fact in Box B.
It is hoped that, once the processes are better understood, the research could lead to the development of drugs that target the perception process to help with the treatment of certain mental illnesses in which the patient’s brains produce false perceptions or disabling fears, such as schizophrenia and post traumatic stress disorder (PTSD). With drug treatments that target the neurons involved when a patient thinks about a certain fear, they could turn off the neurons involved and interfere with the disruptive thought patterns.
The results of the research team’s study appear in Science.
Source: Scripps Research Institute