Intro | Optic Chiasm | Superior Colliculus | Visual Cortex | Lateral Geniculate Nucleus | Optic Nerve | Pulvinar Nucleus | Retina
Part 1: Image-Mapped Tutorial
Part 2: Matching Self-Test
Part 3: Multiple-Choice Self-Test
The visual system is composed of two somewhat separate and parallel pathways. Although these pathways make unique contributions to visual perception and visual behavior, they do exchange information along the way to support the function of the other. Figures 13, 14, and 15 provided a description of the structures involved in the primary visual pathway. This figure will briefly review the flow of information along the primary visual pathway, and discuss the processing that underlies the perception of form, color, brightness, contrast, and depth. More attention, however, will be given to the second visual pathway. This secondary pathway mediates the ability to localize visual objects in space. In addition, along this pathway, visual information is integrated with auditory and somatosensory information and used to control movements made to objects of interest.
| Advanced |
The two visual pathways have been distinguished by a variety of dichotomies or polar processes. Some of the dichotomies used to contrast the second visual pathway with the primary visual pathway include pre-attentive vs. attentive, reflexive vs. deliberate, parallel vs. serial, early warning or detection vs. scrutinizing, global vs. focal, where vs. what, interactive vs. contemplative, external vs. internal. Indeed, these contrasts are excellent descriptions of what is currently known about the functioning of each pathway.
| Suggestions for further study |
Finke, R.A. (1986, March). Mental imagery and the visual system. Scientific American, 254(3), 88-95.
Hubel, D.H. & Wiesel, T.N. (1979, September). Brain mechanisms of vision. Scientific American, 241(3), 150-162.
Kennedy, J.M. (1997, January). How the blind draw. Scientific American, 76-81.
Ramachandran, V.S., et al. (1986, June). The perception of apparent motion. Scientific American, 254(6), 102-109.
Regan, D. et al. (1979, July). The visual perception of motion in depth. Scientific American, 241(1), 136-151.
Treisman, A. (1986, November). Features and objects in visual processing. Scientific American, 255(5), 114B-125.
Wolfe, J.M. (1983, February). Hidden visual processes. Scientific American, 248(2), 94-103.
Wurtz, R.H., et al. (1982, June). Brain mechanisms of visual attention. Scientific American, 246(6), 124-135.
Zeki, S. (1992, Sept.). The visual image in mind and brain. Scientific American, 267(3), 68-76.
http://serendip.brynmawr.edu/bb/blindsight.html
(Seeing What you Don't See)
Bryn Mawr University, Serendipity Project - A demo of blind sight.
http://www.nei.nih.gov/intramural/lsr.htm
(National Eye Institute, Laboratory of Sensorimotor Research)
Mission statement and lab contacts.
http://www.ks.uiuc.edu/~zeller/morphogenesis.html
(Lateral Geniculate Nucleus)
The Theoretical Biophysics Group (TBG), Beckman Institute at
University of Illinois at Urbana-Champaign - Concise and thorough
description and illustration of LGN structure.
http://www.cogsci.soton.ac.uk/bbs/Archive/bbs.bridgeman.html
(A theory of visual stability across saccadic eye movements)
Bridgeman, B., Van der Hejiden, A. H. C., Velichkovsky,
B.M. (1994). Behavioral and Brain Sciences 17 (2):
247-292.
http://www.cogsci.soton.ac.uk/bbs/Archive/bbs.fischer.html
(Express saccades and visual attention)
Fischer, B. & Weber, H. (1993). Behavioral and Brain
Sciences 16 (3): 553-610.
http://www.cogsci.soton.ac.uk/bbs/Archive/bbs.findlay.html
(A model of saccade generation based on parallel processing and
competitive inhibition)
Findlay, J.M. (XXXX). Behavioral and Brain Sciences.