Does Alzheimer’s diminish our inner GPS?

OPINION

In 2014, two Norwegians won the Nobel Prize for throwing light on Alzheimer’s disease. For more than 30 years, husband and wife team Edvard and May-Britt Moser ran rats round in boxes. The pair inserted microscopic probes and sensors into the brains of these rats, and watched what happened in their brains as the rats moved about their cages.

The Mosers discovered that the rats’ brains had a microscopic layer of ‘‘grid cells’’ patterned in an elegant, near perfect, hexagonal or honeycomb lattice, like an elaborately tiled floor.

Certain grid cells sparked whenever a rat crossed certain places as they moved about in their boxes. The cells gave the rat a global positioning system, an inner GPS, and provided it with a map of its surroundings.

Some grid cells represented positions relative to the edge of a box, to let the rat know where it was. The discovery ‘‘was a long drawn-out Eureka moment’’, said Edvard Moser.

Do we humans also have grid cells and maps in our brains?

Scientists can stick probes and sensors in rats’ brains but it is unethical to do that with humans, so researchers had to look elsewhere for evidence of a similar anatomical and functional system.

A number of epileptic patients agreed to have their heads electronically scanned while they were asked to navigate their way through an imaginary city. Tiny points in the brain showed up on the scans.

In later sessions, the subjects were asked to recall their earlier wanderings. Sure enough, scans showed the same tiny points sparked repeatedly as patients imagined revisiting earlier sites.

Here was evidence that we probably have the same navigational system as the rats. This was further confirmed by microscopic work in autopsies.

As in rats, these grid cells almost certainly give us our sense of distance, direction, memory and the ability to navigate our kitchens, bathrooms, gardens, suburbs and cities. They must also let us know where we are on a boat or in a plane.

Which brings us to the recent sad death of Footrot Flats’ creator Murray Ball. Writing about his long struggle with Alzheimer’s, Murray’s widow Pam recalls that she first noticed something amiss while holidaying abroad.

Murray was a stickler for detail but he mistook where their hotel was. Later, ‘‘he could not put anything in the kitchen in the right drawers’’. Later again, he could not find his way to town, or sometimes he would ask, ‘‘Where’s Farmlands?’’ I would say, ‘We’re there’ ‘‘.

Pam recalls that her husband ‘‘would go out on the farm and not return. I would go there with a torch at night looking for him and would always find him sitting on the grass with his dog near him. He would often say to me, ‘Where did you get to?’.’’ It seems to me that Murray Ball’s grid cells slowly atrophied, his mental map fell apart, and his sense of place and direction drifted away. After giving us so much joy, it is sad to learn of his decade-long goodbye.