Dream You Can't Find Your Car? Now Not Thought a Sign of Impending Alzheimer's

I had it again last night.

The dream where I park my car, then go back to find it and it's gone.  I wander around and around but never find it again.

Now a new study has me thinking I'm developing Alzheimer's.

Well, not really.  But researchers at University of California, San Diego School of Medicine have induced this all-too-common human experience – or a close version of it – permanently in rats and from what is observed, hope they can perhaps derive clues about why strokes and Alzheimer's disease can destroy a person’s sense of direction, according to newswise.com.

Scientists have developed a micro-surgical procedure that makes it possible to remove the area of the rat’s brain that contains grid cells and show what happens to this hard-wired navigational system when these grid cells are wiped out. One effect, not surprisingly, is that the rats become very poor at tasks requiring internal map-making skills, such as remembering the location of a resting platform in a water maze test.

“Their loss of spatial memory formation was not a surprise,” the Web site quotes senior co-author Robert Clark, PhD, a professor of psychiatry. “It’s what would be expected, based on the physiological characteristics of that area of the brain,” which is the first brain region to break down in Alzheimer’s disease.

But the rats retained a host of other memory and navigation-related skills that scientists had previously speculated would be destroyed without grid cells.

“The surprise is the discovery of the type of memory formation that was not disrupted by the removal of the grid cell area,” Clark said.

UC San Diego scientists were able to show that even without grid cells rats could still mark spatial changes in their environment. They could, for example, notice when an object in a familiar environment was moved a few inches and they could recognize objects, such as a coffee mug or flower vase, and remember later that they had seen these objects before.

(This is a habit that drives my husband and son crazy.  I know the placement of every object in the kitchen and when even a spoon is moved, I know it.)

Electrical recordings of signals transmitted from the brain suggested that the animals had developed place cells – cells that are believed to convey a sense of location – and that these cells were firing when an animal passed through a familiar place.

“Their place cells were less precise and less stable, but they were present and active,” said Clark, who is also a research scientist at Veterans Affairs San Diego Healthcare System. “That was a surprise because we had removed the spatially modulated grid-cell input to these neurons.”

"Our work shows a crisp division of labor within memory circuits of the brain,” he said. “Removing the grid-cell network removes memory for places but leaves completely intact a whole host of other important memory abilities like recognition memory and memory of fearful events.”

So I guess I'm not losing it all, just most of it!






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