[visionlist] Re: Iceberg effect

Maxim Volgushev maxim at neurop.rub.de
Thu Jan 18 17:20:28 GMT 2007

Dear David,

in my hands, ideas of shaping RF properties in the visual cortex by 
firing threshold
can be traced back to early intracellular recordings by Otto 
Creutzfeldts' group:

Creutzfeldt, Ito - EBR 1968 6:324
"Small excitatory reactions below or near threshold or inhibitions 
against a low spomtaneous
spike activity could often not be made visible with post-stimulus 
histograms, which only gave
a vague impression of the actual subthreshold excitatory or inhibitory 
This could be made visible only with averaged analogue records."  (p. 329)

"The total receptive fields of cortical neurons as determined by the 
post-synaptic polarization
or depolarization were therefore all above 4-5°. If only the output of 
the cells (spike discharges) would
be used for determination of the receptive field, smaller fields 
resulted." (p. 345)

Benevento, Creutzfeldt, Kuhnt - Nature 1972 238:124
" It is posssible that the suprathreshold excitatory response of a 
cortical cell to orientation
and direction is due partly to thalamic excitation which is governed by 
intracortical inhibition.
... cortical cells or columns with different orientation and direction 
sensitivities inhibit each other,
resulting in a restricted suprathreshold orientation or direction 
sensitivity. " (p. 126)

"... intracortical inhibition which shapes the suprathreshold trigger 
feature properties of cortical neurons"
(p. 126).

"Iceberg effect"
With respect to orientation tuning, probably Florentin Woergoetter and 
Christof Koch
(JNeurosci 1991, 11:1959) were the first who used this term:
"... (the effect called "iceberging")..."  (p. 1971).
I can imagine, that in modelling literature it may have being used 
earlier - as a very
natural consequence of integrate-and-fire operation/model.

We have used the term ("tip of the iceberg" effect)
only some years later, in 1996 (Vidyasagar, Pei, Volgushev, TINS 1976, 



>Today's Topics:
>   1. Authors' query: Iceberg effect (David Ferster)
>Message: 1
>Date: Mon, 15 Jan 2007 14:19:23 -0600
>From: David Ferster <ferster at northwestern.edu>
>Subject: [visionlist] Authors' query: Iceberg effect
>To: visionlist at visionscience.com
>Message-ID: <0814E9A0-5C0A-4D8A-BF73-B5DD46CBCCC3 at northwestern.edu>
>Content-Type: text/plain; charset="us-ascii"
>Dear List Members,
>We (Nicholas Priebe, Ian FInn and I) are writing a paper on the  
>effect of threshold on the properties of cortical cells, and we  
>wondering the following:
>Who was the first to use the term "iceberg effect"?
>Who first proposed that threshold might narrow or otherwise affect  
>tuning of the output of cortical cells?
>David Ferster
>Professor, Neurobiology and Physiology
>Northwestern University
>847-491-4137 Phone
>847-491-5211 Fax
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