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Introduction

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  • High-Level Visual Processing Is Concerned with Object Identification

  • The Inferior Temporal Cortex Is the Primary Center for Object Perception

    • Clinical Evidence Identifies the Inferior Temporal Cortex as Essential for Object Recognition

    • Neurons in the Inferior Temporal Cortex Encode Complex Visual Stimuli

    • Neurons in the Inferior Temporal Cortex Are Functionally Organized in Columns

    • The Inferior Temporal Cortex Is Part of a Network of Cortical Areas Involved in Object Recognition

  • Object Recognition Relies on Perceptual Constancy

  • Categorical Perception of Objects Simplifies Behavior

  • Visual Memory Is a Component of High-Level Visual Processing

    • Implicit Visual Learning Leads to Changes in the Selectivity of Neuronal Responses

    • Explicit Visual Learning Depends on Linkage of the Visual System and Declarative Memory Formation

  • Associative Recall of Visual Memories Depends on Top-Down Activation of the Cortical Neurons That Process Visual Stimuli

  • An Overall View

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The images projected onto the retina are generally complex dynamic patterns of light of varying intensity and color. As we have seen, low-level visual processing is responsible for detection of various types of contrast in these images (see Chapters 25 and 26), whereas intermediate-level processing is involved in the identification of so-called visual primitives, such as contours and fields of motion, and the representation of surfaces (see Chapter 27). High-level visual processing integrates information from a variety of sources and is the final stage in the visual pathway leading to conscious visual experience.

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In practice high-level visual processing depends on top-down signals that imbue bottom-up (afferent) sensory representations with semantic significance, such as that arising from short-term working memory, long-term memory, and behavioral goals. High-level visual processing thus selects behaviorally meaningful attributes of the visual environment (Figure 28–1).

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Figure 28–1
The neuronal representation of entire objects is central to high-level visual processing.

Object representation involves integration of visual features extracted at earlier stages in the visual pathways. Ideally the resulting representation is a generalization of the numerous retinal images generated by the same object and of different members of an object category. The representation also incorporates information from other sensory modalities, attaches emotional valence, and associates the object with the memory of other objects or events. Object representations can be stored in working memory and recalled in association with other memories.

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High-Level Visual Processing Is Concerned with Object Identification

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Our visual experience of the world is fundamentally object-centered. Objects are often visually complex, being composed of a large number of conjoined visual features. In addition, the features projected on the retina by an object vary greatly under different viewing conditions, such as lighting, angle, position, and distance.

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Moreover, objects are commonly associated with specific experiences, other remembered objects, other sensations—such as the hum of the coffee grinder or the aroma of a lover's perfume—and a variety of emotions. Animate beings, which are ...

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