In 2005 two Norwegian neuroscientists discovered that rats have a brain region
devoted to spacial memory. These neurons function as a navigation system and
they are called grid cells. They are similar to the “place” cells of the hippocampus
but are in a separate area. The grid cells track the movements of the rats “Thelma”
and “Louise” and remember them. Drs. Edvard and May-Britt Moser operate the
lab for this work at the University of Trondheim. [paraphrased fm N.Y.TIMES science
supplement, 4-30-13].
So…not to worry if your car gets “lost” in the hypermart car park, unless you lose it
EVERY time you go to the car park.
Are you asking if humans have spatial memory? Yes, obviously we do. Are there particular areas of the brain that are important to it? Yes. That isn’t much like GPS, though.
Humans may also be able to sense the direction of the Earth’s magnetic field, although the evidence for this AFAIK is is not very strong and the ability, even if real, seems to be weak and unreliable. Some birds and other animals can certainly do it though.
If this is similar to brain research I heard about on a Radiolab episode about a year ago, it’s not that we literally have a GPS in our brain, but rather that one of the important ways out brains are structured to help us navigate around our environment is by making us subconsciously, automatically impose a mental grid over each space we enter (especially indoor ones, IIRC.)
So, it’s not so much GPS-like, as it is GIS-like – GIS being any kind of spatial software (for mapping, geographic analysis, calculating best routes for fire trucks, etc.). GIS, too, relies on such grids – either implied (in vector GIS, which depends on a coordinate system which can be visualized as a grid, by choosing a certain interval of latitudes and longitudes to display), or direct (in raster GIS, where the whole thing is nothing but a grid of square cells, each cell containing a value.)
GPS and GIS are related: some of the input for GIS data is derived from things located using a GPS; and, the GPS also uses coordinate systems (which, again, are in a way grid-like – but don’t forget the third dimension) to define location.
Except indirectly, in that they both depend on a Cartesian coordinate system (in essence, a “grid”) to function. (In the case of human spatial memory, this is just part of how they work).
The input mechanisms are so different, though – triangulation of distant (satellite-borne) “pings” for GPS, the five senses (especially sight and hearing, but also smell and touch, plus proprioception) for human brains – that your statement “essentially nothing in common” isn’t too far off the mark.
Yeah, there is nothing that’s independent and internal about how a GPS knows where it is. It works by taking a good look at some reference points to find out where it is. A blind GPS is useless.
Yet, a human is supposed to know where it is without the use of it’s senses?
A gyroscopic navigation system works more along the line of knowing its orientation without looking.
That’s what our vestibular system is for.
I find animal navigation to be amazing. It’s well known that some animals use moon- or sun-light for navigation, but I was especially surprised to read that dung beetles can use the Milky Way for navigation!
(My own navigation is rather bad. Walk inside a complicated department store for a while and I’ll have no idea which direction the parking lot is.)
Which assist in “dead reckoning,” in other words. Keeping track of where you are now relative to where you were recently, but not necessarily to absolute locations (whether landmarks, or an abstract coordinate system). GPS can do pseudo-dead reckoning, but only by relying on that same, absolute-coordinate locational awareness, and someone (a person walking or in a vehicle) to move it from one place to another. Humans aren’t so limited.
I think both proprioception and the inner-ear vestibular systems are a big part of this “dead reckoning” aspect of human brain/body navigation. (And the two systems overlap a lot – I think proprioception is basically “vestibular” plus “muscle awareness”).
I don’t think this is true at all. We don’t impose a Cartesian mental grid. We have some idea where landmarks are based on the direction from us and how far away they are. This is much more analogous to a polar coordinate system It takes a lot of patient work and trigonometry to convert that to a Cartesian grid. You can see this in how we give people directions when driving. We give them instructions on which direction to go with reference to local landmarks. Go past the kmart then turn left. Even with modern GPS navigation systems we get similar sorts of direction with respect to local landmarks.
If you look at old maps or England they are just roads with lists on landmarks along the way. It is not until the 15th century that you start to see any line like what we consider modern maps. This is because instruments and math have been developed to give us the modern Cartesian maps we know and use today.
This is not how GPS works. GPS satellites do not send pings they continuously send out a time reference. The gps receiver then uses this information to determine how far away the satellite is away. There is no information about what direction the satellite is. Triangulation is what you do when you get your orientation merit badge in boy scouts. You use a compass to determine the heading to two or more local landmarks and then draw lines on a map from those local landmarks.
Well, calling what the brain’s grid cells do “like a Cartesian grid” is an inexact analogy, but it’s pretty accurate, according to the research I cited.
I never said GPS receivers “send” anything,but I probably shouldn’t have used the word “ping”. The only analogy to sonar I meant to evoke was the idea of a timed signal where time is converted to distance.
And, I’m sorry, but triangulation is exactly how this is done in GPS.
Maybe some people do, but my family totally lacks it. We have no gene for the sense of direction. I still get lost in the neighborhood where I have lived for seven years.
I have to memorize each and every building on a street to get anywhere.
I stand corrected! You are right. Because “triangulation” has taken on multiple, extended meanings in English (e.g., this), while “trilateration” is still “stuck” with just its literal meaning, “triangulation” was the first word that came to my mind (as I’m sure it does to many) to describe determining a location based on how it relates to several known points. But I’ll strive to be more precise. GPS does of course use distances, not angles, and so it is indeed “trilateration.”
Well in some cities I have a built-in GPS and in others I do not. In San Francisco I have no trouble navigating the hills and neighborhoods. In Pittsburgh every time I rely on my sense of direction I find myself halfway to Cleveland.
Maybe you are like those rats “Thelma” and “Louise” in Norway. I wonder how
they can “dead reckon” in a completely dark container without visual cues.
Perhaps they rely on smell and echo-location as well as those grid cells. I did not read the news article thoroughly.
For this to be strictly true, a GPS receiver would need its own “atomic” clock with accuracy comparable to the clocks on board GPS satellites. That would be necessary to calculate the exact signal travel time, which would yield a precise distance from the satellite.
To avoid the considerable complexity and cost of this, normal receivers don’t calculate their distance from individual satellites. Instead, they use pairs of satellites and measure the difference in arrival time of the signals from each. Each such time difference measurement allows the receiver to place itself on a hyperbola (or in 3 dimensions a “hyberbloid of revolution”). Calculating the intersection of several of these allows an accurate single position to be determined.
Compared to true trilateration, this requires that one additional satellite be “in view”. But that’s rarely an issue, and the huge reduction in receiver cost makes this a good tradeoff.
Good point. That’s why there are sometimes TWO solutions for the calculations – you could be here, but you might be there – but, almost always, only one of those solutions is anywhere near the surface of the Earth.
I have no sense of direction. Away from familiar streets, I might as well be driving in a bowl. I have trouble with spatial concepts too. I think it has to do with one eye that has only 10% vision. The other eye is basically okay. But I can’t see three demensionally. Since the problem is congenital, I’ve adapted to other signals.