McConnell response to my query about the statement in her home page. The message below is exactly the way I got it. She did not reply when I sked for more specific references.

Hubel & Wiesel's work never showed anything that can support her claim. She is probably refering to their suggestion that the smallest area of the visual cortex which contains neurons responsive to all orientation (much larger area than what is typically called columns), is the smallest unit that is required to analyze a small portion of the sensory world (see here).

From: "Susan McConnell" 
To: "Yehouda Harpaz" 
Sent: Wednesday, January 09, 2002 9:52 PM
Subject: Re: Minimal unit


>Hi,
>
>This is taken from your page
>http://www.stanford.edu/group/skmlab/research/rsum.html
>
>    "This radial stack of neurons forms the cortical column, a minimal unit
>    of neurons and connections required to analyze a small portion of  
>    the sensory world."
>What is the evidence for this staement?
>
>Thanks,
>
>Yehouda Harpaz
>
oh gosh, i'm not sure what the direct evidence is -- basically from
hubel & wiesel's work in the 60s and 70s...
--
>
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Susan K. McConnell, Ph.D.
Professor
Department of Biological Sciences
Stanford University
Herrin Labs 115
385 Serra Mall
Stanford, CA 94305-5020
>
Phone:  (650) 725-8786
Fax:  (650) 725-9832
E-Mail:  suemcc_stanford.edu
http://www.stanford.edu/group/skmlab/