Origins: Brain and Self Organization

By Karl Pribram | Go to book overview

Visual pathways supporting perception and action in the
primate cerebral cortex

Melvyn A. Goodale

University of Western Ontario, London, Canada

Behavioral and electrophysiological evidence suggests a new interpretation of the division of labor between the ventral and dorsal streams of visual processing in primate cerebral cortex. It is suggested that the ventral stream mediates the perception of objects while the dorsal stream mediates the on-line control of skilled actions directed at those objects.


Ungerleider and Mishkin [1] first suggested the possibility that the visual pathways projecting from striate cortex to other cortical regions could be divided into two relatively independent 'streams' of visual processing. According to their original account, a ventral stream, arising in striate cortex and eventually terminating in the inferotemporal region, plays a critical role in the identification and recognition of objects, while a dorsal stream, projecting from striate cortex to the posterior parietal cortex, mediates the localization of those same objects. Since its introduction just over ten years ago, this distinction between object vision and spatial vision ('what' versus 'where') has become one of the most familiar functional dichotomies in visual neuroscience.

With the discovery that the retinal projections to the parvocellular (P) and magnocellular (M) layers of the dorsal lateral geniculate nucleus (LGNd) have different response properties and that these cytologically-defined channels remain segregated at the level of primary visual cortex and perhaps beyond (for review, see [2,3˙˙]), attempts were made [4,5] to relate the differences in the properties of these channels to the distinction between two streams of processing made earlier by Ungerleider and Mishkin. According to at least one account [5], the P pathway, which had been linked to color and form vision, was thought to be the main contributor to the ventral stream (and thus object vision), while the M pathway, which was believed to be responsible for motion perception and stereopsis, was thought to provide the main input to the dorsal stream (and thus spatial vision). If such an account were true, then the primate visual system (within the geniculostriate route, at least) would consist of two independent and parallel sets of inputs that arise in the retina and remain segregated even at the highest levels of visual processing.

Although empirical support for this idea was initially quite compelling, recent evidence from a broad range of studies has challenged this simple account of visual processing. The results of psychophysical studies in monkeys with discrete lesions of the parvo- and magnocellular layers of LGNd [6-8] suggest that the distinctions between the kinds of visual processing carried out by these two pathways are not as sharp as was originally thought (with the exception of color vision which appears to depend almost entirely on the P pathway [6,7]). In fact, even the earlier electrophysiological studies of the responses of ganglion and geniculate cells had shown considerable overlap in the range of effective stimuli (for review, see [3˙˙]). The current consensus is that the difference between the two channels is largely one of relative sensitivity within the temporal and spatial domains, with the M pathway favoring high temporal and low spatial frequencies, and the P pathway, low temporal and high spatial frequencies. In summary, the specializations of the parvo and magno pathways are perhaps best understood in terms of a trade-off amongst the different requirements of spatial, wavelength, and temporal processing [2,3˙˙] and thus it is difficult to argue that one channel is specialized for object vision and the other for spatial vision.

Recent electrophysiological studies by John Maunsell and his colleagues [9,10˙˙,11] suggest that the anatomical segregation of the magno and parvo inputs to the dorsal and ventral streams is also much less clear-cut than was originally thought. Thus, while inactivation of the magnocellular layers of the LGNd almost always reduces the responsivity of cells in the middle temporal area (MT), some cells in this dorsal stream area are also affected by inactivation of the parvocelluar layers, although to a lesser degree [9]. In V4, however, which is part of the ventral stream, most neurons are affected equally by inactivation of either the parvocellular or magnocellular layers of the LGNd [10˙˙], a result which is consistent with the earlier observation that inputs from both of these cytological subdivisions are present in the blob and interblob regions of V1 [11]. In summary then, both the ventral and


LGNd--dorsal lateral geniculate nucleus; LIP--lateral intraparietal sulcus; M--magnocellular; MST--medial superior temporal area; MT--middle temporal area; P--parvocellular.


Notes for this page

Add a new note
If you are trying to select text to create highlights or citations, remember that you must now click or tap on the first word, and then click or tap on the last word.
One moment ...
Default project is now your active project.
Project items

Items saved from this book

This book has been saved
Highlights (0)
Some of your highlights are legacy items.

Highlights saved before July 30, 2012 will not be displayed on their respective source pages.

You can easily re-create the highlights by opening the book page or article, selecting the text, and clicking “Highlight.”

Citations (0)
Some of your citations are legacy items.

Any citation created before July 30, 2012 will labeled as a “Cited page.” New citations will be saved as cited passages, pages or articles.

We also added the ability to view new citations from your projects or the book or article where you created them.

Notes (0)
Bookmarks (0)

You have no saved items from this book

Project items include:
  • Saved book/article
  • Highlights
  • Quotes/citations
  • Notes
  • Bookmarks
Cite this page

Cited page

Citations are available only to our active members.
Buy instant access to cite pages or passages in MLA, APA and Chicago citation styles.

(Einhorn, 1992, p. 25)

(Einhorn 25)

1. Lois J. Einhorn, Abraham Lincoln, the Orator: Penetrating the Lincoln Legend (Westport, CT: Greenwood Press, 1992), 25,

Note: primary sources have slightly different requirements for citation. Please see these guidelines for more information.

Cited page

Bookmark this page
Origins: Brain and Self Organization
Table of contents

Table of contents



Text size Smaller Larger Reset View mode
Search within

Search within this book

Look up

Look up a word

  • Dictionary
  • Thesaurus
Please submit a word or phrase above.
Print this page

Print this page

Why can't I print more than one page at a time?

Full screen
/ 718

matching results for page

    Questia reader help

    How to highlight and cite specific passages

    1. Click or tap the first word you want to select.
    2. Click or tap the last word you want to select, and you’ll see everything in between get selected.
    3. You’ll then get a menu of options like creating a highlight or a citation from that passage of text.

    OK, got it!

    Cited passage

    Citations are available only to our active members.
    Buy instant access to cite pages or passages in MLA, APA and Chicago citation styles.

    "Portraying himself as an honest, ordinary person helped Lincoln identify with his audiences." (Einhorn, 1992, p. 25).

    "Portraying himself as an honest, ordinary person helped Lincoln identify with his audiences." (Einhorn 25)

    "Portraying himself as an honest, ordinary person helped Lincoln identify with his audiences."1

    1. Lois J. Einhorn, Abraham Lincoln, the Orator: Penetrating the Lincoln Legend (Westport, CT: Greenwood Press, 1992), 25,

    New feature

    It is estimated that 1 in 10 people have dyslexia, and in an effort to make Questia easier to use for those people, we have added a new choice of font to the Reader. That font is called OpenDyslexic, and has been designed to help with some of the symptoms of dyslexia. For more information on this font, please visit

    To use OpenDyslexic, choose it from the Typeface list in Font settings.

    OK, got it!

    Cited passage

    Thanks for trying Questia!

    Please continue trying out our research tools, but please note, full functionality is available only to our active members.

    Your work will be lost once you leave this Web page.

    Buy instant access to save your work.

    Already a member? Log in now.

    Author Advanced search


    An unknown error has occurred. Please click the button below to reload the page. If the problem persists, please try again in a little while.