For decades, scientists have debated whether rapid eye movement sleep - the phase where dreams appear - is directly involved in memory formation. Now, a study provides evidence that REM sleep does, indeed, play this role in mice.
In this new study, the researchers used optogenetics, a recently developed technology that enables scientists to target precisely a population of neurons and control its activity by light. For this study, the neurons in the
hippocampus were targeted (hippocampus being the structure that is critical for memory formation during wakefulness and is known as the 'GPS system' of the brain).
To test the long-term spatial memory of mice, the scientists trained the rodents to spot a new object placed in a controlled environment where two objects of similar shape and volume stand. Spontaneously, mice spend more time exploring a novel object than a familiar one, showing their use of learning and recall. When these mice were in REM sleep, however, the researchers used light pulses to turn off their memory-associated neurons to determine if it affects their memory consolidation. The next day, the same rodents did not succeed the spatial memory task learned on the previous day. Compared to the control group, their memory seemed erased, or at least impaired.
Source: http://science.sciencemag.org/content/352/6287/812
