BE35 PLT ATTRIBUTES AIRSPACE VIOLATION AND IMPAIRED MENTAL ABILITY TO HYPOXIA RESULTING FROM FLT AT 12500 FT.

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IN RETROSPECT; IT IS CLR TO ME THAT I ENCOUNTERED AN ADVANCED CASE OF HYPOXIA IN MY VFR DSCNT. I HAD BEEN CRUISING FOR ABOUT 4 HRS WITH FLT FOLLOWING AT 12500 FT; AND THE FLT AT THAT ALT HAD BEEN PROGRESSING UNEVENTFULLY. WHEN I ANNOUNCED TO CTR THAT I WOULD COMMENCE A VFR DSCNT; I WAS HANDED OFF TO ANOTHER SECTOR. THIS IS WHEN THINGS WENT AWRY. I THINK I MAY HAVE HEARD WRONG OR SELECTED A WRONG FREQ; BUT MY ATTEMPTS AT CONTACT WENT NOWHERE; AND SOMEHOW I WAS UNABLE TO RETURN TO MY PREVIOUS CTLR. THIS SEEMS INCREDIBLE FOR A PLT WITH MY LEVEL OF EXPERIENCE; BUT; WHILE FLYING THE AIRPLANE WAS NO PROB; HANDLING EVEN THE MOST SIMPLE MENTAL TASKS BECAME ALMOST IMPOSSIBLE. AS A RESULT; I ENTERED CLASS B AIRSPACE WITHOUT A CLRNC. I AM 73 YRS OLD; BUT AM IN EXCELLENT HEALTH; HAVE NEVER SMOKED; AND DO NOT DRINK ALCOHOL. BUT I REALIZE NOW THAT; OBVIOUSLY; PROLONGED FLT; EVEN AT THE LEGAL ALT OF 12500 FT; CAN HAVE A VERY DETRIMENTAL EFFECT ON ONE'S MENTAL CAPACITY. ALSO IN RETROSPECT; I REMEMBER THAT IT WAS RATHER WARM AT ALT. THIS WOULD HAVE RAISED THE DENSITY ALT EVEN FURTHER. I RECEIVED A REAL EDUCATION; AND ONE OF THE FIRST THINGS I WILL INVEST IN WILL BE PORTABLE OXYGEN EQUIP.