I was on Lithium Carbonate 600mg daily, 300mg in the morning and 300mg in the evening. I experienced the "brain fog" as you say and I was forgetting simple things and I just didn't like it, and I was on it for a few months and it never subsided like the other side effects that I experienced when I first started taking it, it helped with my manic episodes and my anger but the "brain fog" was just too much for me. so I told my doc and I stopped on my own and when I saw him again and he then put me on 1250mg daily of Depakote and that was worse. I am now seeing a new doc on the 7th of this month and I am hoping to get different results. Good luck to you dear and I hope you have better results than I did.