A new experiment reveals that mice can recall false memories that were implanted during sleep, according to researchers.

This is the first time new conscious memories have been implanted in mice while they slept.

During sleep, brains replay the events of the day, reliving activities of the day, in an accelerated manner. The reason for this behavior, although uncertain, could be a form of practice for the mind, as it learns new activities. This is also true of mice, which will relive events including exploration of new areas.

Place cells, found in the brains of both mice and humans, are believed to be vital to the recognition or memory of new places. These cells, within the brains of mice, were monitored using electrodes, as the rodents were exploring new area. Researchers identified place cells that only fired in specific areas.

As the creatures slept, computers monitored the replay of the day, recognizing specific place cells. When certain place cells were activated, the mouse was provided with stimulation to its pleasure centers. Upon waking, the rodent headed directly, and quickly, toward the location represented  by place cells that received reward stimuli.

"The mouse develops a goal-directed behavior to go toward the place. It proves that it's not an automatic behavior. What we create is an association between a particular place and a reward that can be consciously accessed by the mouse," Karim Benchenane of the Industrial Physics and Chemistry Higher Educational Institution in France said.

Place cells provide mice with some sense of location, however, the degree to which they do this is uncertain, since the rodents also utilize vision and other sense to determine where they are at any given moment.

Less dramatic associations can be implanted in human beings during sleep, such as smoking cessation treatments that cause people to smell unpleasant odors when they encounter tobacco smoke.

Spatial memories are among the best understood of all forms of recall. Other memories, such as learning skills, are unlikely to be implanted using similar methods, researchers report.

"I think this is a really important step towards helping people with memory impairments or depression. It is surprising to me how many neurological and psychiatric illnesses have something to do with memory, including schizophrenia and obsessive compulsive disorder," said Loren Frank at the University of California, San Francisco.

It is possible this research could one day lead to developing methods to alter memories of traumatic experiences that negatively impact a person's life.

The analysis regarding spatial memory in mice was detailed in the journal Nature Neuroscience.

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