Perception and Attention - Computational Explorations in Cognitive Neuroscience - page 222

Chapter 8

Perception and Attention

Contents

8.1 Overview

8.1 Overview ......................227
8.2 BiologyoftheVisualSystem............228
8.2.1 TheRetina..................228
8.2.2 TheLGNoftheThalamus..........230
8.2.3 PrimaryVisualCortex:V1 .........230
8.2.4 TwoVisualProcessingStreams .......232
8.2.5 The Ventral Visual Form Pathway: V2, V4,
andIT....................233
8.2.6 TheDorsalWhere/ActionPathway .....233
8.3 PrimaryVisualRepresentations..........234
8.3.1 BasicPropertiesoftheModel........235
8.3.2 ExploringtheModel.............237
8.3.3 SummaryandDiscussion ..........240
8.4 Object Recognition and the Visual Form Pathway 241
8.4.1 BasicPropertiesoftheModel........243
8.4.2 ExploringtheModel.............246
8.4.3 SummaryandDiscussion ..........255
8.5 SpatialAttention:ASimpleModel ........257
8.5.1 BasicPropertiesoftheModel........258
8.5.2 Exploring the Simple Attentional Model . . 261
8.5.3 SummaryandDiscussion ..........268
8.6 SpatialAttention:AMoreComplexModel....269
8.6.1 Exploring the Complex Attentional Model . 269
8.6.2 SummaryandDiscussion ..........272
8.7 Summary ......................272
8.8 FurtherReading ..................2 73

In this chapter we explore models of visual percep-
tion from the lowest level cortical representations to
the more abstract high-level, spatially invariant object
representations. We demonstrate how attentional ef-
fects emerge at multiple levels of representation and in
the interactions between different specialized process-
ing streams. We focus on vision because it is the most
studied and relied-upon of our senses, and similar prin-
ciples are likely to apply to other senses.
As we observed in chapter 7, perceptual processing
is conceived of as a sequence of transformations that
emphasize some aspects of the perceptual input while
collapsing across others. Our somewhat unitary and
transparent subjective visual experience is constructed
from a wide array of processing areas, each specialized
to some extent for a particular aspect of the visual world
(e.g., shape, color, texture, motion, depth, location, and
so on). Thus, the general structural principles of spe-
cialized, hierarchical processing streams discussed in
chapter 7 are quite relevant here.
We focus primarily on two pathways, one that
emphasizes object identity information and collapses
across other aspects of the input such as spatial loca-
tion (the “what” pathway), and one that emphasizes spa-
tial location information while collapsing across object
identity information (the “where” pathway). These two
pathways interact with each other, and produce a com-
plex pattern of spatial and object-based attention .The
principles derived from exploring this subset of phe-

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