Hidden memories in the sleep-deprived brain: The consequences of sleep loss for hippocampal plasticity and memory

Sleep loss has a detrimental impact on brain function, particularly on cognitive processes responsible for storing and retrieving memories with detailed contextual and spatial information. It appears that even a brief period of sleep deprivation may already result in memory deficits such as forgetting where you parked the car last evening. Experimental rodent studies revealed that sleep deprivation hampers memory processing via disturbing critical biological processes in a specific brain region called the hippocampus. However, how sleep loss impacts the storage and retrieval of contextual and spatial information in the hippocampus remains to a large extent still unknown. For that reason, we conducted a series of studies in mice with an emphasis on how sleep deprivation impairs hippocampal memory processing. We found that sleep deprivation affects connections between brain cells (neurons) in the hippocampus. Furthermore, in contrast to general belief, we demonstrated sleep deprivation does not lead to the loss of information, but rather makes memories stored under sleep deprivation conditions difficult to remember. These findings suggest that the location of your parked car is still stored in your brain but in an inaccessible (i.e., hidden) state, that does not allow you to retrieve the information when you are searching for your car. Using a combination of state-of-the-art approaches, we successfully managed to make these ‘hidden’ memories accessible again. Overall, these findings provided novel insight into the molecular processes responsible for the observed memory impairments after a lack of sleep.