# What does “diffuse slowing” mean in the context of EEG and Alzheimer's?

Horvath et al. (2018) mention that:

The disappearance of posterior dominant alpha rhythm and the diffuse slowing in AD (alzheimer disease) are easily detectable EEG signs for the experienced eyes.

What does diffuse slowing mean in this context? I tried searching it up online but I only found papers that take its meaning for granted.