Paper available: review of circuitry underlying mature orientation selectivity, experiments and models

[Ken Miller]

The following paper is now available at
    ftp://ftp.keck.ucsf.edu/pub/ken/fm_final.ps.gz (compressed postscript)
    ftp://ftp.keck.ucsf.edu/pub/ken/fm_final.pdf   (pdf)
or  http://www.keck.ucsf.edu/~ken                  (click on 'Publications')

This is a preprint of an article to appear in Annual Reviews of
Neuroscience, Vol. 23 (2000).  

(Note: A review I announced about two weeks ago focused on
*development* of orientation selectivity.  This review, in contrast
focuses on the structure of the circuitry underlying mature
orientation-selective responses.)

----------------------------------------

Neural Mechanisms of Orientation Selectivity in the Visual Cortex
             David Ferster, Northwestern University
   Kenneth D. Miller, University of California, San Francisco
  to appear in Annual Reviews of Neuroscience, Vol. 23 (2000).

ABSTRACT:

The origin of orientation selectivity in the responses of simple cells
in cat visual cortex serves as a model problem for understanding
cortical circuitry and computation. The feedforward model of Hubel and
Wiesel posits that this selectivity arises simply from the arrangement
of thalamic inputs to a simple cell. Much evidence, including a number
of recent intracellular studies, supports a primary role of the
thalamic inputs in determining simple cell response properties
including orientation tuning. However, this mechanism alone cannot
explain the invariance of orientation tuning to changes in stimulus
contrast. Simple cells receive push-pull inhibition: ON inhibition in
OFF subregions and vice versa. Addition of such inhibition to the
feedforward model can account for this contrast invariance, provided
the inhibition is sufficiently strong. The predictions of
"normalization" and "feedback" models are reviewed and compared to the
predictions of this modified feedforward model and to experimental
results. The modified feedforward and the feedback models ascribe
fundamentally different functions to cortical processing.




Ken
 
        Kenneth D. Miller               telephone: (415) 476-8217
        Dept. of Physiology		fax: (415) 476-4929
        UCSF                            internet: ken at phy.ucsf.edu
        513 Parnassus			www: http://www.keck.ucsf.edu/~ken
        San Francisco, CA 94143-0444