Geography Reference
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navigation, which together seem to code the proximity and direction to the goal.
The three regions were the medial prefrontal cortex and the right entorhinal region,
neuronal activity in one of them positively correlated and in the other negatively
correlated with goal proximity, and the bilateral posterior parietal cortex, where
activity was correlated with the egocentric direction to goals.
With such a differentiated picture it makes sense to assume that different
navigation tasks access different spatial abilities. Hartley et al. observed brain
activity in people finding their way in an unfamiliar (virtual) environment and
in people following a familiar route in another (virtual) environment [ 75 ] . The
wayfinders showed higher activities in the anterior hippocampus, while the route
followers showed higher activities in the head of caudate. The prior coincides
with the prior assumption that the hippocampus is involved in place learning, and
provides response to location within a spatial representation. The latter is consistent
with an assumption of the caudate supporting action-based representations, and
providing fast response to actions instead of locations. Their observations suggest
that (at least) two representations are available for navigation, an action-based
which is more efficient in learned environments and a location-based which is more
efficient in unknown environments.
A review of behavioral and neuroscientific findings in rodents and humans
by Chan et al. brought up that environmental objects can act as landmarks for
navigation in different ways [ 23 ] . They proposed a taxonomy for conceptualizing
object location information during navigation. This taxonomy consists of:
￿
Objects as visual beacons for navigation indicating a nearby en-route target
location.
￿
Objects used as associative cues indicating a nearby location with an associated
navigational action.
￿
Objects as visual cues to maintain or regain orientation.
￿
Objects used as an environmental reference frame for navigation, which are
geometric properties of larger objects that can provide a frame for organizing
spatial information, such as alignment operations (for example, rats seem to
prefer geometric cues over object cues for orientation [ 25 ] ).
The distinction between smaller objects—visual beacons or associative cues—and
larger objects, or rather object geometries such as walls, becomes even more
relevant with research testing whether one of them is preferred. Hartley et al. [ 76 ] ,
for example, have geometrically altered the boundaries of a (virtual) environment
between two visits of participants. The first time participants encountered a cue
object in a simple rectangular enclosure and a distant visual cue for orientation.
The second time, after a brief break outside of the environment, participants were
brought back and asked to mark the place where the cue had been. On some trials
the geometry (size, aspect ratio) of the arena was varied between presentation and
testing. Hartley et al. report:
Responses tended to lie somewhere between a location that maintained fixed distances from
nearby walls and a location that maintained fixed ratios of the distances between opposing
walls. The former were more common after expansions and for cued locations nearer to
 
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