Melvyn A. Goodale
Professor
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Canada Research Chair in Visual NeuroScience |
In a series of theoretical articles, my colleague, David Milner, and I have proposed that separate, but interacting visual systems have evolved for the perception of objects on the one hand and the control of actions directed at those objects on the other. This 'duplex' account of high-level vision suggests that 'reconstructive' approaches and 'purposive-animate-behaviorist' approaches need not be seen as mutually exclusive, but as complementary in their emphases on different aspects of visual function. Evidence from both humans and monkeys has shown that this distinction between vision for perception and vision for action is reflected in the organization of the visual pathways in primate cerebral cortex. Two broad "streams" of projections from primary visual cortex have been identified: a ventral stream projecting to the inferotemporal cortex and a dorsal stream projecting to the posterior parietal cortex. Both streams process information about the structure of objects and about their spatial locations - and both are subject to the modulatory influences of attention. Each stream, however, uses this visual information in different ways. The ventral stream transforms the visual information into perceptual representations that embody the enduring characteristics of objects and their relations. Such representations enable us to identify objects, to attach meaning and significance to them, and to establish their causal relations - operations that are essential for accumulating knowledge about the world. In contrast, the transformations carried out by the dorsal stream deal with moment-to-moment information about the location and disposition of objects with respect to the effector being used and thereby mediate the visual control of skilled actions directed at those objects. Both streams work together in the production of adaptive behavior. The selection of appropriate goal objects and the action to be performed depends on the perceptual machinery of the ventral stream, but the execution of a goal-directed action is carried out by dedicated on-line control systems in the dorsal stream.
Cant, J.S. & Goodale, M.A. (2007). Attention to form or surface properties modulates different regions of human occipitotemporal cortex. Cerebral Cortex, 17, 713-731. Ganel, T. & Goodale, M.A. (2003). Visual control of action but not perception requires analytical processing of object shape. Nature, 426, 664-667. Goodale, M.A. & Milner, A.D. (2004). Sight Unseen: An Exploration of Conscious and Unconscious Vision. Oxford: Oxford University Press. 135pp. James, T.W., Culham, J., Humphrey, G.K., Milner, A.D., & Goodale, M.A. (2003). Ventral occipital lesions impair object recognition but not object-directed grasping: An fMRI study. Brain, 126, 2463-2475. Milner, A.D. & Goodale, M.A. (2006). The Visual Brain in Action. 2nd Edition. Oxford: Oxford University Press. 297pp. Whitney, D., Goltz, H., Thomas, C.G., Gati, J., Menon, R., & Goodale, M.A. (2003). Flexible retinotopy: Motion dependent position coding in the visual cortex. Science, 302, 878-881.
