Parallel Processing in the Visual System

I. The Classification of Retinal Ganglion Cells.- 1. From the Beginning: Ganglion Cell Classification to 1966.- 1.1. Conduction Velocity Groupings in the Optic Nerve.- 1.2. Receptive Field Studies of Retinal Ganglion Cells.- 1.2.1. Parametric Analyses of Receptive Fields.- 1.2.2. Feature Extraction Analyses of Receptive Fields.- 1.3. Morphological Classifications of Ganglion Cells.- 1.4. Function or Phylogeny as a Basis for Ganglion Cell Classifications?.- 2. The Y/X/W Classification of Cat Retinal Ganglion Cells.- 2.1. The Development of the Y/X/W Classification.- 2.1.1. Description of the X/Y Difference.- 2.1.2. Conduction Velocity Correlates of X and Y Cells.- 2.1.3. The W-Cell Grouping.- 2.1.4. Morphological Classes of Cat Ganglion Cells.- 2.2. The Y/X/W Classification: Categories and Taxa.- 2.2.1. Evidence for Choice of Categories.- 2.2.2. Evidence for Choice of Taxa.- 2.3. The Interpretation of Variation: A Central Problem in Cell Classification.- 2.3.1. "Single" and "Multiple" Interpretations of Variation.- 2.3.2. Sources of Variation in the Properties of Ganglion Cells.- 2.3.3. A Multiple Interpretation of Variation in the Properties of Ganglion Cells.- 2.4. A Two-Group (XY/W) Classification of Cat Retinal Ganglion Cells.- 2.5. Two Notes on the Classification of Nerve Cells.- 2.5.1. Incommensurable Classifications.- 2.5.2. Mixed Classifications: The Best of Both Approaches?.- 3. Ganglion Cell Classification in Other Species.- 3.1. In the Monkey.- 3.1.1. Conduction Velocity Groupings.- 3.1.2. Physiological Classifications: Parametric and Feature Extraction.- 3.1.3. The W-like System of Ganglion Cells.- 3.1.4. Morphological Classifications.- 3.1.5. Summary.- 3.2. In the Rat.- 3.2.1. Conduction Velocity Groupings.- 3.2.2. Receptive Field Correlates: Is There an X-like Group?.- 3.2.3. Morphological Classifications.- 3.2.4. Summary.- 3.3. In the Rabbit.- 3.3.1. Conduction Velocity Groupings.- 3.3.2. The Feature Extraction Classification of Rabbit Ganglion Cells.- 3.3.3. More Parametric Analyses.- 3.3.4. Summary.- 3.4. In Other Mammals: Tree Shrew, Goat, and Ground Squirrel.- 3.4.1. Tree Shrew.- 3.4.2. Goat and Ground Squirrel.- 3.5. In Nonmammals: Frog, Toad, Pigeon, Eel, and Mudpuppy.- 3.5.1. Frog and Toad.- 3.5.2. Pigeon.- 3.5.3. Eel and Mudpuppy.- II. On the Methodology of Classification.- 4. Toward Certainty, Objectivity, or Testability? Two Notes on Alternative Methodologies of Classification.- 4.1. Alternative Methodologies of Classification: Their Basis in the Concerns of Classifiers.- 4.1.1. Nominalism and Realism.- 4.1.2. Different Realist Approaches: Toward Certainty, Objectivity, or Testability.- 4.1.3. Summary.- 4.2. Three Stages in the Taxonomy of Animals.- 4.2.1. Aristotle's Taxonomy: Metaphysical Essentialism.- 4.2.2. Physical Typology.- 4.2.3. The Influence of the Theory of Evolution.- 5. Epistemological Background: Inductivism, Essentialism, Instrumentalism, Falsificationism, and Paradigms.- 5.1. Inductivism.- 5.2. Essentialism (Typology).- 5.3. Instrumentalism.- 5.4. Falsificationism.- 5.5. Paradigms and Revolutions.- 5.6. A Falsificationist Approach to the Classification of Neurons.- III. The Impact of Ganglion Cell Classification.- 6. On the Understanding of Visual Processing in the Diencephalon.- 6.1. The LGN of the Cat.- 6.1.1. Evidence of Parallel Processing in the LGN.- 6.1.2. The W-Cell Relay in the dLGN.- 6.1.3. The Medial Interlaminar Nucleus.- 6.1.4. The vLGN.- 6.1.5. The Lamination of the dLGN.- 6.1.6. Morphology of Relay Cells.- 6.1.7. Cortical Projections of Y-, X-, and W-Class Relay Cells.- 6.1.8. Corticogeniculate Projections.- 6.2. The LGN of Primates.- 6.2.1. X/Y Analysis of Parvo- and Magnocellular Laminae.- 6.2.2. Other Components of the LGN.- 6.2.3. Corticofugal Projections.- 6.2.4. Summary.- 6.3. Other Species.- 6.3.1. The LGN of the Rat.- 6.3.2. The LGN of the Tree Shrew.- 6.3.3. The LGN of the Mink.- 6.3.4. Summary.- 6.4. Qualifications to the Parallel Processing Model of the LGN.- 6.5. The Hypothalamus.- 6.6. The Pulvinar: Evidence for an Extrageniculate W-Cell Relay.- 7. On the Understanding of the Visual Centers of the Midbrain.- 7.1. The Midbrain/Forebrain Division of the Visual Pathways: By Branching or Grouping of Ganglion Cells?.- 7.2. The Superior Colliculus of the Cat.- 7.2.1. Early Evidence: Conduction Velocity Analysis of the Retinocollicular Projections.- 7.2.2. Receptive Field Correlates: Hoffmann's Three-Channel Model of the Retinocollicular Projection.- 7.2.3. The Influence of the Visual Cortex and of Visual Deprivation on the Superior Colliculus.- 7.2.4. Qualifications and Limitations.- 7.3. The Superior Colliculus of the Monkey.- 7.4. The Superior Colliculus of Other Species.- 7.4.1. The Rat.- 7.4.2. The Rabbit.- 7.4.3. The Hamster.- 7.4.4. The Opossum.- 7.4.5. Summary.- 7.5. Other Midbrain Centers.- 7.5.1. The Pretectal Nuclei and the Nucleus of the Optic Tract.- 7.5.2. Nuclei of the Accessory Optic Tract and Nucleus Raphe Dorsalis.- 8. On the Understanding of Visual Cortex.- 8.1. Cat Visual Cortex: Processing of Geniculate Input.- 8.1.1. Parallel Pathways to Different Cortical Areas.- 8.1.2. Parallel Organization of Area 17: Correlations between Afferent Input and Receptive Field Properties.- 8.1.3. Parallel Organization of Area 17: Analyses of Its Lamination.- 8.1.4. Corticofugal Projections of Areas 17, 18, and 19.- 8.2. Primate Visual Cortex: Processing of Geniculate Input.- 8.2.1. Parallel Organization of Area 17.- 8.2.2. Organization of the Prestriate Cortex.- 8.3. Cortical Afferents from Extrageniculate Sources.- 8.3.1. Sources of Extrageniculate Afferents in the Cat.- 8.3.2. Sources of Extrageniculate Afferents in the Monkey.- 8.3.3. Functional Significance of the "Second" Visual Pathway.- 8.4. Models of Neuronal Processing within the Striate Cortex: An Argument against Serial Processing.- 8.4.1. The Simple/Complex Model of Serial Intracortical Processing.- 8.4.2. Synaptic Latencies: A Second Line of Evidence for Serial Processing?.- 8.4.3. Summary.- 8.5. Future Work: The Importance of the Classification and Terminology Used for Cortical Cells.- 9. On the Understanding of Retinal Topography: A "Two-Axis" Model of Mammalian Retina.- 9.1. The Problem: The Variability of Retinal Topography.- 9.2. A Two-Axis Model of the Topography of Mammalian Retina.- 9.3. The Vertical Axis: The Nasotemporal Division of Retina.- 9.3.1. Historical Note: The Nasotemporal Division of Human Retina.- 9.3.2. The Nasotemporal Division of the Retina in the Monkey.- 9.3.3. The Nasotemporal Division of the Retina in the Common Cat.- 9.3.4. The Nasotemporal Division of the Retina in the Siamese Cat.- 9.3.5. The Nasotemporal Division of the Retina in Marsupials, the Rabbit, Rodents, and the Fox.- 9.3.6. Summary.- 9.4. The Horizontal Axis: The Visual Streak.- 9.4.1. The Visual Streak of the Rabbit Retina.- 9.4.2. The Visual Streak of the Cat Retina.- 9.4.3. Evidence of a Visual Streak in the Monkey and Other Primates.- 9.4.4. The Opossum: An Exception?.- 9.4.5. Summary.- 9.5. The Fovea or Area Centralis: A Specialization at the Junction of the Two Axes.- 9.5.1. The Fovea Centralis of the Monkey and Other Primates.- 9.5.2. The Area Centralis of the Cat.- 9.5.3. Evidence of an Area Centralis in the Rabbit Retina.- 9.5.4. Summary.- 9.6. Two Regional Specializations Related to the Axis of Nasotemporal Division.- 9.6.1. Nasal-Temporal Gradients in the Properties of Ganglion Cells.- 9.6.2. A Vertical Streak?.- 9.7. How Generally Can the Model be Applied?.- 9.7.1. The Generality of the Area Centralis.- 9.7.2. The Generality of the Visual Streak.- 9.7.3. The Generality of the Nasotemporal Division of the Retina.- 9.7.4. The Siamese Cat: A Case to Prove Two Points.- 9.8. Functional Significance of Regional Specializations.- 9.8.1. The Nasotemporal Division of the Retina.- 9.8.2. The Fovea or Area Centralis and the "Vertical Streak".- 9.8.3. Nasal-Temporal Differences in Ganglion Cell Properties.- 9.8.4. The Visual Streak.- 9.8.5. Retinal Topography: The Influence of Visual Environment and Phylogenetic Heritage.- 9.8.6. Significance of the Two-Axis Model: A Ground Plan for the Topography of Mammalian Retina.- 10. On the Understanding of the Visual Pathways' Dependence on the Visual Environment.- 10.1. Introduction: Three Starting Points.- 10.1.1. Amblyopia: The Clinical Starting Point.- 10.1.2. The Philosophical Starting Point: Rationalism and Empiricism.- 10.1.3. Animal Models of Amblyopia: The Neurobiologists' Starting Point.- 10.1.4. Summary.- 10.2. Effects of Visual Deprivation on the LGN of the Cat.- 10.2.1. The "Loss" of Y Cells from the LGN of Visually Deprived Cats: Its Nature, Morphological Correlates, and Cause.- 10.2.2. An Abnormality of Geniculate X Cells in Visually Deprived Cats: A "Direct" Effect of Deprivation.- 10.2.3. Other Evidence of a "Direct" Mechanism in Visual Deprivation.- 10.2.4. The Effect of Visual Deprivation on W-Class Relay Cells.- 10.2.5. The Effect of Immobilizing the Eye.- 10.3. Effects of Visual Deprivation on Cat Retinal Ganglion Cells.- 10.4. Effects of Visual Deprivation on the SC of the Cat.- 10.5. Effects of Visual Deprivation on the Visual Cortex of the Cat.- 10.5.1. Which Stimulus Selectivities Can Develop without Visual Experience?.- 10.5.2. Determinants of Ocular Dominance.- 10.5.3. Eccentricity-Related Differences in the Modifiability of Orientation Stripes.- 10.6. Effects of Visual Deprivation in Other Species.- 10.6.1. In the Monkey.- 10.6.2. In the Tree Shrew.- 10.7. Conclusion: W, X, and Y Components of the Neural Basis of Amblyopia.- 11. On the Understanding of Visual Psychophysics and Behavior.- 11.1. Introduction.- 11.2. The Focal/Ambient Division of Visual Function and Its Neural Basis.- 11.2.1. The Focal/Ambient Division of Visual Function.- 11.2.2. Evidence in Humans.- 11.2.3. Evidence in Monkeys.- 11.2.4. Evidence in Cats.- 11.2.5. Summary.- 11.3. Evidence of Distinct X and Y Contributions to Focal Vision.- 11.3.1. The Dual-Mechanism Hypothesis of the Perception of Form and Motion.- 11.3.2. Qualifications.- 11.3.3. The Oblique Effect: A Psychophysical Correlate of X-Cell Function.- 11.4. The Neural Representation of Visual Perception: A Comment.- 12. Extensions and Limits of the Parallel Processing Analysis.- 12.1 Parallel Processing in the Somatosensory Pathways.- 12.1.1. Classification of Somatosensory Afferents.- 12.1.2. Channeling of Submodalities through Spinal Cord and Brain Stem.- 12.1.3. The Parallel Organization of Somatosensory Thalamus.- 12.1.4. The Parallel Organization of Somatosensory Cortex.- 12.1.5. Summary.- 12.2. Notes on Other Sensory Pathways.- 12.2.1. The Auditory Pathways.- 12.2.2. The Chemical Senses.- 12.3. Ideas and Their Limits.- 12.4. "Parametric Systematics": An Approach to the Understanding of Sensory Pathways.- 12.4.1. Two Terms: Reductionist and "Holistic".- 12.4.2. The Technical Limits of Ideas.- 12.4.3. A "Parametric Systematics" for Sensory Biology.- References.