Jim,
Your problem could be related to the "adrenochrome hypothesis"proposed by Abram Hoffer, M.D. who wrote a book on Orthomolecular Medicine.
He proposed the use of Niacin for many with these cognitive difficulties.
If you do try niacin begin with very low doses and slowly increase the dosage over a period of weeks. It is a miracle vitamin (B3) for some people.
You should also have a nutritional blood test, an evaluation for hypoglycemia, and an evaluation for hidden infection, thyroid disorder, and hidden allergies.
Check out Dr. David Perlmutter's website and book BrainRecovery .com and his brain nutrient powder called Brain Sustain.