The gradual loss of cells in the brain's cortex could be decreasing sleep quality in older adults, leading to poorer long-term memory.
Bryce Mander and Matthew Walker at the University of California, Berkeley, and their group asked healthy adults to memorize a list of words, recall some of them ten minutes later, and recall the rest the next morning. Adults in their late 60s and their 70s performed worse on the test, and showed significant reductions in the slow brain waves that are associated with deep sleep, compared with those around the age of 20. The extent of deep-sleep disruption was related to the degree of memory impairment, and these differences were, in turn, linked with a reduction of grey matter in the medial prefrontal cortex.
The findings suggest that deterioration of this part of the brain diminishes the slow brain waves, which are implicated in memory consolidation, impairing the ability to solidify new memories.
Nature Neurosci. http://dx.doi.org/10.1038/nn.3324 (2013)