@bigj,
My brain fog includes difficulty communicating (especially word loss), difficulty thinking clearly and making decisions, inability to concentrate/pay attention, forgetfulness, memory loss, slow processing and reaction time of what is said and done, and mental exhaustion. It’s not consistent, but comes and goes. For me, stress and fatigue bring on brain fog. The worse the stress or the longer I’m fatigued without rest/sleep, the worse the brain fog.