Hi Sameer, the brain fog is like...a feeling that my brain isn't working, my thoughts don't click together properly, I am unfocused and my thoughts are scattered. It's hard to be motivated to do tasks. And I know deep down I usually function better than this, when I'm not in POIS.
The lessening of the brain fog made me mentally sharper, my thoughts were more concrete and I could focus my attention better, including on the people around me and conversations. My ability to communicate was better.
Hope that helps..