Biomedical Engineering Reference
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to perception, such as information pickup, direct perception, and perception/action
complementarity (see, for example, [
31
,
72
,
107
]).
On the other hand, people often rely on knowledge of remote locations to set
future goals, to orient toward unseen locations, and to imagine themselves (and
other people) in different places. Such knowledge consists of remembered informa-
tion that is not perceptually available for immediate inspection. Although ecological
approaches may be able to address and describe this type of knowledge (see for
example, [
41
,
42
]), it is generally more common in the literature to consider spatial
memory as involving internal representations of environmental structure [
29
]. By
this view, enduring spatial knowledge is the result of mental processing and storage
of environmental and internal information. Most researchers accept a three-tiered
description of enduring spatial knowledge that includes: (a) relatively rudimentary
(and arguably nonspatial) memory for landmarks and features, (b) route knowledge
of how places are interconnected, typically without regard to the metric distances
and directions between them, and (c) configuration (or survey) knowledge of global
metric relations among places in an environment. Of course, sensory contributions to
any of these types of knowledge may be qualitatively different, which can complicate
our discussion considerably.
Regardless of whether spatial knowledge enables action in the moment or is stored
for subsequent use, it is clear that in order to be useful, spatial knowledge must
coordinate the disposition of the knower with characteristics of the environment.
Thus in laying-out the sensory bases for environmental cognition, we make a primary
distinction between sensory information that provides either: (a) external information
about the nature of one's environment, or (b) internal (or idiothetic) information
about the status of one's body or effectors. After discussing these sources of sensory
information, we turn briefly to a consideration of non-sensory information that is
internally generated, such as attention allocation and other cognitive factors.
1.1 External Sensory Information
Vision provides a direct, rich, and precise source of spatial information, and it is
undoubtedly the most researched sensory modality with respect to environmental
knowledge and navigation. Like many other external senses, the visual system can
provide detailed and useful information about the spatial layout of the immediate
environment without significant bodily movement (see [
24
,
80
] for a review of visual
cues that enable apprehension of layout). The layout of an environment, including
relative directions, distances, and scale can be accurately perceived and remembered
from a stationary viewpoint (e.g., [
92
]), from brief glimpses of images of a spatial
layout [
118
], and even from symbolic media such as maps [
105
] and gestures [
3
].
Frequently however, visual information about an environment comes from move-
ment through it—from the optic flow generated from changes in one's position and
heading. As one changes position (e.g., moving forward or backward) optic flow pat-
terns radiate from a focus of expansion or contraction. As one changes orientation
