The research in this laboratory is directed at understanding the functional organization of cortical areas, functional modules, and local circuits that underlie pattern, color, and object discrimination in the primate visual system. The current research is directed towards an understanding of the intermediate levels of form and color processing in areas V2, V4 and posterior inferotemporal cortex.
|Optical recording and pathway tracing in macaque visual cortex. A. Visual stimuli used for differential activation of chromatic and luminance B. Differential image of activations in area V1 'blobs' and V2 'thin stripes' due to chromatic stimulation. C. Oriented luminance grating stimuli. D. Orientation-specific activations in V1 ' interblobs' and V2 ' interstripes' and 'thick stripes'. E. Segregation and integration of V2 thin stripe (dark) and interstripe (bright) axonal inputs to area V4. F. Segregation and integration of V2 thin stripe (bright) and interstripe (dark) axonal inputs to area V4.|
A wide variety of anatomical and physiological techniques are used to investigate the organization of visual cortex. Optical recording of intrinsic cortical signals is used to map the functional organization of restricted portions of areas V1, V2, or V4. Difference-images, generated by comparing images of cortex under different visual stimulation conditions, are used to identify local regions of activated neurons. These functional maps are then used to guide neuroanatomical tracer injections into identified modules. The patterns of axonal termination in cortical area V4 following separate "color" and "form" injections in area V2 provides evidence for both the segregation and the local integration of color and form inputs in V4. Computer interfaced microscopy, image processing, and three-dimensional computer graphics are used to analyze the complex anatomical relationships.
A second line of inquiry concerns the neuro-developmental changes that occur in dorsolateral prefrontal and orbitofrontal cortex following neonatal damage to medial temporal lobe structures. These studies seek to identify changes in cortical architecture, connections, and neurochemistry, which underlie the cognitive and social-emotional changes that occur in lesioned monkeys. Their long-term goal is to understand the anatomical changes which occur in human neuro-developmental disorders such as schizophrenia and autism.
Felleman, DJ, Van Essen, DC. (1991) Distributed hierarchical processing in primate cerebral cortex. Cerebral Cortex 1:1-47.
DeYoe, EA, Felleman, DJ, Van Essen, DC, McClendon, E. (1994) Multiple processing streams in occipito-temporal visual cortex. Nature 371:151-154.
Felleman, DJ, Burkhalter, A, Van Essen, DC. (1997) Cortical connections of areas V3 and VP of macaque monkey extrastriate visual cortex. J. Comp. Neurol. 379:21-47.
Felleman, DJ, Xiao, Y, McClendon, E. (1997) Modular organization of occipito-temporal pathways: cortical connections between visual area 4 and visual area 2 and posterior inferotemporal ventral area in macaque monkeys. J. Neurosci. 17:3185-3200.
Xiao, Y, Wang, Y, Felleman, DJ. (2003) A spatially organized representation of colour in macaque cortical area V2. Nature 421: 535 - 539 (30 Jan 2003).
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