Bilberry and Pycnogenol are the 2 main herbs, with ginko to help facilitate delivery to brain circulation. Grape Seed extract can be a substitute for Pycnogenol, but I prefer the effects of pycnogenol.
The Blood brain/barrier protects toxins from entering the brain. The brain as the central nervous system is the primary system of the body that interfaces with all other systems, organs, and tissues. As such it can affect all these other endpoint tissues via direct routes or by modulating hormones, feedback loops, immune system function, etc. By allowing subtances into the brain more easily, it upregulates inflammation of tissues which leads to degenerative changes. There is some interesting research coming out now about schizophrenia, inflammation, and nervous tissue destruction. It can linked to diseases like MS, Parkinsons, Alzheimers, etc to simple brain fog.