An accurate ‘here’

ScienceDaily has an item (here) on a paper by Valerio and Taube, Path integration: how the head direction signal maintains and corrects spatial orientation in Nature Neuroscience. The research shows that there are two processes for correcting a navigation error, resetting and remapping.

There are two types of cell involved in following a path: the head direction cells in the thalamus that fire depending on the direction you are facing, and the place cells in the hippocampus that fire depending on where you are located.

Taube explains that the two populations — the head direction cells and the place cells — talk to one another. “They put that information together to give you an overall sense of ‘here,’ location wise and direction wise,” he says. “That is the first ingredient for being able to ask the question, ‘How am I going to get to point B if I am at point A?’ It is the starting point on the cognitive map.”

What happens when the animal finds it has made an error in navigation. That depends on the size of the error.

When the animal makes a small error and misses the target by a little, the cells will reset to their original setting, fixing on landmarks it can identify in its landscape. “We concluded that this was an active behavioral correction process, an adjustment in performance,” Taube says. “However, if the animal becomes disoriented and makes a large error in its quest for home, it will construct an entirely new cognitive map with a permanent shift in the directional firing pattern of the head direction cells.” This is the “remapping.”

I have long found a sense of direction very interesting. (This probably comes from growing up on the prairies where prominent landmarks are few and keeping track of my heading, with a sort of metaphorical compass, was very important.) I find being lost a very distinct and extremely nasty state of consciousness. It is a kind of loss of contact with the world – a little girl inside cries in panic, “I don’t know which way is north”. Perhaps this feeling is produced by knowing that the head cells need a permanent shift but not yet being able to make the right shift.

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