Changes in cortical slow wave activity in healthy aging.

A number of studies have demonstrated enhanced slow wave activity associated with pathological brain function e.g. in stroke patients, schizophrenia, depression, Morbus Alzheimer, and post-traumatic stress disorder. However, the association between slow wave activity and healthy aging has remained largely unexplored. This study examined whether the frequency at which focal generators of delta waves appear in the healthy cerebral cortex changes with age and whether this measure relates to cognitive performance. We investigated 53 healthy individuals aged 18 to 89 years and assessed MEG during a resting condition. Generators of focal magnetic slow waves were localized. Results showed a significant influence of age: dipole density decreases with increasing age. The relationship between cognitive performance and delta dipole density was not significant. The results suggest that in healthy aging slow waves decrease with aging and emphasize the importance of age-matched control groups for further studies. Increased appearance of slow waves as a marker for pathological stages can only be detected in relation to a control group of the same age.