Friday, May 08, 2009

The oriented-in-space place

Drawing a mental blank is a drawback of a busy day; being unable to draw a mental map of your current location is a red flag for trouble. While getting lost in your work rates high performance reviews, getting lost while driving maybe a sign of dementia.

Arriving safely at home at the end of our day requires the proper functioning of an oriented-in-space place in our brains located just behind and above the ear. This medial superior temporal area (MST) is charged with personal global positioning, providing our brain with continual updates on our current location in space.

Unfortunately, the MST is particularly vulnerable to the cellular destruction associated with Alzheimer's Disease(AD), leaving its victims unstuck in their once familiar world. This deficit has been dubbed 'motion blindness'; the the resultant inability to navigate, even through one's own home, leads to a tragic loss of independence.

Here's another scary consequence. While early AD victims may remember street names and the basic rules of the road, there are certain driving skills that lapse early in the course of the disease based on MST dysfunction. I remember an office visit where my elderly patient arrived slightly late for her appointment. She sat down in the chair with a sigh, then proceeded to recount her harrowing drive over during which, per her report, she sideswiped several cars on both sides of the narrow streets near my office while trying to guide her car down the middle of the road. She had no sense at all of where her car ended relative to those parked by the curb.

I don't know what was more disturbing--her zigzag navigation of a potentially lethal weapon or her relative indifference to destruction that she left in her path.

1 comment:

Mauigirl said...

One of the first signs my father was getting dementia was his getting lost on his way back from his part-time job that he had after his retirement. At first we didn't realize it because he'd always had a lousy sense of direction!