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Moving beyond “the brain’s GPS” to understand navigation

navigation-1048294_1920As succinct descriptions go, there’s something inspired about “the brain’s GPS,” which is shorthand for a set of neurons collectively responsible for constructing mental maps of where in the world we are at any given time.

The problem is, it’s not particularly good shorthand. As researchers Kiah Hardcastle, Niru Maheswaranathan, Lisa Giocomo, PhD, and Surya Ganguli, PhD, came to realize, not many of our neurons actually track position per se. The same goes for neurons thought to track other navigational variables, like speed or the direction your head is facing: Rather than encode any one variable, neurons encode some mix of those things, they reported recently in Neuron.

For instance, some neurons fire in response to a complex mix of position and head direction. Stranger still, there appear to be neurons that respond only to position or head direction – not both – when an animal is plodding along, but track both position and head direction when it starts to run.

Those conclusions are at odds with the conventional neuroscience wisdom, as I describe in a Stanford News story:

…one of the take-home messages of this work is that there isn’t a good mathematical model for the brain’s navigation system. Existing models make assumptions that simply are not compatible with their results. 'We need to rethink basically what the mechanism is,' [Giocomo] said.

And the consequences could run even deeper:

[T]he cells of the brain do not necessarily think the way we think, in which case it could be misguided to assume the brain navigates using the same tools – speedometers, compasses, and so forth – as we would. 'The variables that the brain cares about may not be the same as the variables that the mind cares about. There may be a discrepancy between those. And if there is, then we somehow have to break free of the prejudices of our mind in order to understand the brain,' Ganguli said.

It’s not as succinct as “the brain’s GPS,” but it may be just as inspired.

Previously: MAP-ing the brain: Technology offers new insight on how the brain functions and Brain connectivity fluctuates more than previously thought, new Stanford research shows
Photo by DariuszSankowski

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