- •CONTENTS
- •PREFACE
- •ABSTRACT
- •1. INTRODUCTION
- •2.1. Background
- •2.1.1. Anatomical Asymmetry of Brain
- •2.1.2. Hemispheric Lateralization of Cerebral Functions
- •2.1.3. Hemispheric Asymmetry Using Reaction Time
- •2.1.4. Reaction Time Task Based Upon Double Crossed Projections
- •2.2.1. Purpose
- •2.2.2. Methods
- •2.2.2.1. Participants
- •2.2.2.2. Apparatus
- •2.2.2.3. Procedures
- •2.2.3. Results
- •2.2.4.Discussion
- •2.3.1. Purpose
- •2.3.2. Materials and Methods
- •2.3.2.1. Participants
- •2.3.2.2. Apparatus
- •2.3.2.3. Procedures
- •2.3.3. Results
- •2.3.4. Discussion
- •2.4.1. Purpose
- •2.4.2. Methods
- •2.4.2.1. Participants
- •2.4.2.2. Apparatus and Procedures
- •2.4.3. Results
- •2.4.4. Discussion
- •2.5.1. Purpose
- •2.5.2. Methods
- •2.5.2.1. Participants
- •2.5.2.2. Apparatus
- •2.5.2.3. Procedures
- •2.5.3. Results
- •2.5.4. Discussion
- •2.5.4.1. Effect of Luminance on Hemispheric Asymmetry
- •2.5.4.2. Effect of Contrast on Hemispheric Asymmetry
- •2.5.4.3. Effect of Practice on Visual Field Difference
- •2.5.4.4. Effect of Subject Number Size
- •2.6.1. Purpose
- •2.6.2. Methods
- •2.6.2.1. Participants
- •2.6.2.2. Apparatus
- •2.6.2.3. Procedures
- •2.6.3. Results
- •2.6.4. Discussion
- •2.7.1. Purpose
- •2.7.2. Methods
- •2.7.2.1. Participants
- •2.7.2.2. Apparatus
- •2.7.2.3. Procedures
- •2.7.3. Results
- •2.7.4. Discussion
- •3.1. Background
- •3.1.1. Startle Response
- •3.1.2. Prepulse Inhibition
- •3.2. Purpose
- •3.3. Methods
- •3.3.1. Participants
- •3.3.2. Apparatus
- •3.3.3. Prepulse
- •3.3.4. Startle Stimulus
- •3.3.5. Recordings Of Blinking
- •3.3.6. Procedures
- •3.4. Results
- •3.4.1. Measurements of the Response Amplitude
- •3.4.2. Typical Example of PPI of the Blink Response
- •3.4.3. Responses to Chromatic and Achromatic Prepulses
- •3.5. Discussions
- •3.5.1. Three Types of Blink Reflexes
- •3.5.2. Eyelid and Eye Movements During Blinking
- •3.5.3. Neural Circuit for PPI
- •3.5.4. Effect of Change in Luminance
- •3.5.5. Cortical Contributions to PPI
- •4.1. Two Visual Pathways
- •4.2. Two Visual Streams
- •4.3. Three Hierarchies of the Brain
- •4.4. Limbic System
- •4.5. Dual Processing Circuits of Visual Inputs
- •4.7. Blindsight and Extrageniculate Visual Pathway
- •4.8. Amygdala and the Affective Disorders
- •4.9. Amygdala Regulates the Prefrontal Cortical Activity
- •4.10. Multimodal Processing for Object Recognition
- •5. CONCLUSION
- •ACKNOWLEDGMENTS
- •REFERENCES
- •ABSTRACT
- •INTRODUCTION
- •1.1. Newton on the Properties of Light and Color
- •1.2. Interaction of the Color-Sensing Elements of the Eye
- •1.4. The Mechanisms of Mutual Influence of Sense Organs
- •Ephaptic Connections
- •Irradiation Effect. The Rule of Leveling and Exaggeration
- •Connections between Centers
- •The Role of the Vegetative Nervous System
- •Sensor Conditioned Reflexes
- •The Changing of Physiological Readiness of the Organism to Perception
- •1.1. The History of the Principle of the Being and Thinking Identity
- •Parmenides
- •Plato
- •Aristotle
- •Descartes
- •Necessity
- •Sufficiency
- •Leibnitz
- •Wittgenstein
- •Modern Analytic Tradition
- •2) Sufficiency
- •1) Necessity
- •2.2. Critical Arguments against Experience
- •2) Historical Development of the Scientific Fact (L. Fleck)
- •2.3. The Myths about Experience: Passivity and Discreteness of Perception
- •The Thesis of Underdeterminacy as a Corollary of Perception Activity
- •The Principle of Empirical Holism
- •3.2. The Color and Cognition
- •Example of Presetting Influence on the Possibility of Observation
- •CONCLUSION
- •REFERENCES
- •ABSTRACT
- •What Is Colour?
- •Biological Colourations in Living Organisms
- •Pigment Based Colouration
- •Structure Based Colourations
- •Bioluminescence: Colourations from Light
- •Functional Anatomy of Colour Vision across the Species
- •Colour Vision in Non-Humans
- •Colour and the Human Visual System
- •Deceptive Signalling or Camouflage
- •Advertising and Mate Choice
- •Repulsive Signalling
- •Additional Functions
- •Colour Perception in Man: Context Effects, Culture and Colour Symbolism
- •Context Effects in Colour Perception
- •Colour Perception and Cultural Differences
- •Colour Symbolism and Emotions
- •REFERENCES
- •INDIVIDUAL DIFFERENCES IN COLOUR VISION
- •ABSTRACT
- •1. INTRODUCTION
- •2. COMPARATIVE STUDY OF THE FUNDAMENTALS
- •3. DIFFERENCES BETWEEN MEN AND WOMEN
- •A. STIMULUS GENERATING SYSTEM
- •B. PSYCHOPHYSICAL TEST
- •C. SAMPLE
- •4. DIFFERENCES IN THE MODEL OF COLOUR VISION
- •4. CONCLUSION
- •ACKNOWLEDGMENTS
- •REFERENCES
- •ABSTRACT
- •1. INTRODUCTION
- •2.1. Evidences For and Against the Segregation Hypothesis
- •2.1.1. Early Visual Areas
- •2.1.2. Higher Visual Areas
- •2.2. Evidences For and Against a Specialized Color Centre in the Primate
- •CONCLUSION
- •ACKNOWLEDGMENTS
- •REFERENCES
- •ABSTRACT
- •3. THE PHENOMENAL EVIDENCES FOR COLOUR COMPOSITION
- •4. MIXING WATER AND MIXING COLOURS
- •REFERENCES
- •1. INTRODUCTION
- •2.2. Variational Approaches
- •2.3. Statistics-Based Anisotropic Diffusion
- •2.4. Color Image Denoising and HSI Space
- •2.5. Gradient Vector Flow Field
- •3. COLOR PHOTO DENOISING VIA HSI DIFFUSION
- •3.1. Intensity Diffusion
- •3.2. Hue Diffusion
- •3.3. Saturation Diffusion
- •4. EXPERIMENTS
- •5. CONCLUSIONS
- •REFERENCE
- •REFERENCES
- •ABSTRACT
- •INTRODUCTION
- •CAROTENOIDS AS COLORANTS OF SALMONOID FLESH
- •SEA URCHIN AQUACULTURE
- •Effect of a Diet on Roe Color
- •Relationship between Roe Color and Carotenoid Content
- •REFERENCES
- •ABSTRACT
- •INTRODUCTION
- •History & Current Ramifications of Colorism/Skin Color Bias
- •Colorism in the Workplace
- •CONCLUSION
- •REFERENCES
- •ABSTRACT
- •ACKNOWLEDGMENT
- •REFERENCES
- •ABSTRACT
- •ACKNOWLEDGMENTS
- •REFERENCES
- •INDEX
In: Color Perception: Physiology, Processes and Analysis |
ISBN: 978-1-60876-077-0 |
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Editors: D. Skusevich, P. Matikas, pp. 161-183 |
© 2010 Nova Science Publishers, Inc. |
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Chapter 5
COLOR-SENSITIVE NEURONS
IN THE VISUAL CORTEX:
AN INTERACTIVE VIEW OF THE VISUAL SYSTEM
Maria C. Romero,1 Ana F. Vicente,1 Maria A. Bermudez1
and Francisco Gonzalez1,2
1Department of Physiology, School of Medicine, University of Santiago de Compostela, Santiago de Compostela, Spain
2Service of Ophthalmology, Complejo Hospitalario Universitario de Santiago de Compostela, Santiago de Compostela, Spain
ABSTRACT
Classically, different physical attributes of the visual stimulus were thought to be solved in parallel by interdependent neuronal populations conveying information from the retina to the parietal and temporal cortical areas. According to this assumption, while neurons in the dorsal areas of the visual system were mainly related to the analysis of motion and spatial information, those located at the more ventral positions were mostly associated to shape and color processing. However, although this functional segregation between visual areas has been supported for several decades, there is also strong experimental evidence suggesting an alternative task-driven view of the visual system. According to this more recent perspective, neuronal responses in cortical visual areas can be simultaneously dependent on more than one single visual attribute. As far as color perception plays a central role in visual recognition, it could be assumed that colorsensitive neurons would be also involved in the analysis of some other critical visual attributes. In agreement with this idea, it has been shown that V1 double opponent cells respond to edges defined not only by chromatic and luminance differences, but also by the orientation of their receptive fields. Furthermore, results from many electrophysiological and neuroimaging studies have also demonstrated that colorsensitive neurons in V2 and V3, modulate their responses depending on diverse physical attributes of the stimulus such as the stimulus direction, orientation, luminance and shape, revealing the simultaneous contribution of magnoand parvocellular inputs from the Lateral Geniculate Nucleus (LGN) at different levels of the visual system. At higher visual areas, several authors have reported the existence of multi-sensitive neurons.
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Middle Temporal (MT) neurons, in the dorsal stream, are sensitive to motion spots defined by single or combined changes in texture and color. In the ventral stream, responses to both, color and orientation have been described in V4 and the inferotemporal cortex. Additionally, results from several studies blocking the magnoand parvocellular projections from the LGN to V4 have shown that these two channels can simultaneously contribute to neuronal responses at this level of processing. All these data evidence that even sharply-color-tuned neurons can show color-related responses modulated by many other visual attributes.
1. INTRODUCTION
Over the past few decades, the functional role of many cortical regions has been elucidated. Thus, the specific role of these regions was labeled according to the new findings from different approaches and methods. Following such a multidisciplinary perspective, sensory and cognitive processes were thought to be achieved by a number of neuronal populations working in parallel, each solving one specific component of the analysis. It has been suggested that the information about color, shape, depth and motion is processed in many cortical regions, mainly organized into two independent cortical pathways: the dorsal and ventral streams of the visual system (Ungerleider & Mishkin, 1982; Haxby et al., 1992, 1994, 2000; Ungerleider & Haxby, 1994; Courtney et al., 1996; Ungerleider et al., 1998). According to this assumption, the occipitotemporal cortex would be composed of separate functionally discrete regions, processing visual complex stimuli (Ishai et al., 1999; Haxby et al., 2000; Nystrom et al., 2000), such as faces or other biologically relevant stimuli (Sergent et al., 1992; Haxby et al., 1994, 1996; Clark et al., 1996; Courtney et al., 1996; Sams et al., 1997; Ungerleider et al., 1998). The functional distribution of these visual areas gave rise to the ‘segregation’ hypothesis. From this hypothesis, object perception implies the analysis of different physical attributes such as color, shape or motion, all developed by different neuronal populations. Thus, while neurons in the ventral stream would code information about color and shape, neurons in the dorsal stream would be more involved in motion and spatial processing (Desimone et al., 1985; Goodale & Milner, 1992; Kiper et al., 1997).
Although this idea was classically supported for many decades (Ungerleider & Mishkin, 1982; Mishkin et al., 1983), the whole theory was nevertheless against the basic requirements for a complex visual processing. Whenever the observer fixates a particular object, its visual system must combine, at least, the colorand shape-related information in it to allow higher perceptual mechanisms. As possible combinations between attributes become infinite when we consider the entire visual world, the idea of independent cells specialized in all different combinations seems unlikely. Instead, numerous evidences strongly support the idea of a neuronal cooperation at different stages of the visual system. Named as the binding problem, the idea of how our brain can combine multiple bits of information arriving from separated brain areas to build up a single coherent percept remains under debate.
Since the 1980s, several authors have tried to explain the binding problem (Julesz, 1986; Treisman, 1986). In general, it was accepted that different visual properties could be encoded in different feature maps during a preattentive stage of perception. Later on, attention would work as a filter, selecting and linking these specific features by both, increasing the salience of the attended stimulus, and reducing the perceived surrounding field (Reynolds & Desimone, 1999).
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From an alternative approach, other authors (Optican & Richmond, 1987; Gray, 1999; Singer, 1999) have focused their studies on the temporal aspects of this problem. Their data suggest that neural oscillations and synchronous signals are present in the brain, and that neurons can use these signals to strengthen their synaptic communications. This interactive system could explain the communication occurred between nearby neurons, but also between those separated by several cortical columns, or even areas, in the visual cortex (Eckhorn et al., 1988; Gray & Singer, 1989). According to this perspective, cells located at different areas can show coherence in their responses to specific stimuli, favouring a comprehensive perception of the visual object.
Whatever the particular mechanism is involved in this task, visual information must be integrated at some level to allow a complete processing, and cooperative strategies between the neuronal populations are required. One of the most prolific approaches to the study of neuronal cooperation in the visual system comes from the analysis of color perception.
2. COLOR PROCESSING IN THE PRIMATE
BRAIN—GENERAL OVERVIEW
Generally speaking, humanand non human-primate color decoding systems follow similar anatomical distributions (Sereno et al., 1995), showing high functional homology in both, the eye, and early visual stages (DeValois et al., 1974). Although from the primary visual cortex (V1) this homology decreases (Heywood et al., 1991; Zeki et al., 1991; Rizzo et al., 1993; McKeefry & Zeki, 1997; Beauchamp et al., 1999; Zeki et al., 1998), the parallelism is still evident, and therefore neurophysiological studies in monkeys have provided a powerful tool to understand the processes involved in human color perception.
Primate color vision starts in the retinal color-tuned photoreceptors, named as cones, which spatial density peaks in the fovea, declining rapidly towards the periphery. Cones with spectral sensitivities to long (red-type) and half wavelengths (green-type) are shared by most mammals (Mollon, 1989), but only primates show an additional third type of cones, sensitive to short wavelengths (blue-type) (Dartnall et al., 1983; Nathans et al., 1986). A linear model in which cell responses are proportional to the sum (rectified sum for complex cells) of these three types of cones can describe quite well the chromatic properties of cells in the Lateral Geniculate Nucleus (LGN) and the visual cortex (Derrington et al., 1984). The color opponent centre-surround structure found in the receptive field (RF) of LGN neurons filters the information that will be send to cortical structures, projecting chromatic information through low-pass channels, and luminance information through spatial band-pass channels (De Valois et al., 1977; Derrington et al., 1984).
Most of the studies in both, humans and apes have been traditionally consistent with the idea that the color processing is concentrated in ventral occipitotemporal areas. Thus, the analysis of patients with brain injury at this level have shown that deficits in color perception can be mainly associated with lesions in the ventral cortex (Meadows, 1974; Zeki, 1990), although different cortical areas have been equally involved. Studies in patients with cerebral achromatopsia suggested that the occipitotemporal cortex, together with the fusiform and lingual gyri, and the Inferotemporal cortex (IT) can be crucial structures for color processing (Damasio et al., 1980; Zeki, 1990; Beauchamp et al., 2000; Girkin & Miller, 2001).