Connectionists: New paper on why modules evolve, and how to evolve modular neural networks

[Juyang Weng]

Dear Jeff Clune:

Thank you for pointing to the URL.  I quote some statements below in two 
paragraphs.   Although I agree that the genome has made a "best guess" 
when a zygote forms, it is simple-minded to attribute the modularity of 
the brain, even at the birth time, primarily to "evolution of 
modularity" as you put it.  In other words, unlike the zygote, the brain 
of a new born is no longer simply the "best guess" of the genome.  The 
body of the new born has played a fundamental role in the formation of 
the modularity inside the newborn's brain.   Namely, the "emergence" or 
development, is the key process for brain's modularity in the newborn 
and of course also in the later life.

If you have a chance to read our computational model of the DEVELOPMENT 
of a brain-inspired network DN, at least computationally DN does not 
need to attribute its emergence of modularity to anything other than a 
set of cell mechanisms.  This is because of the cell-centered role of 
the genes, known as genomic equivalence.  For example, each cell grows 
and connects according to signals from other cells in its neighborhood 
(not primarily genes!).  Many biological experiments have shown how 
autonomous cells (whose properties are
to some degree genome specified) communicate to migrate, differentiate, 
form tissues (e.g., cortex), and connect.  In our DN model, such cell 
behaviors give rise to surprising brain-like capabilities when sensory 
and motor signals are present.

By attention to "emergence" in the paragraphs I quoted below.

-John

"The existence of modules is recognized at all levels of the biological 
hierarchy. In order to understand what modules are, why and how they 
emerge and how they change, it would be necessary to start a joint 
effort by researchers in different disciplines (evolutionary and 
developmental biology, comparative anatomy, physiology, neuro- and 
cognitive science). This is made difficult by disciplinary 
specialization. [...] we claim that, because of the strong similarities 
in the intellectual agenda of artificial life and evolutionary biology 
and of their common grounding in Darwinian evolutionary theory, a close 
interaction between the two fields could easily take place. Moreover, by 
considering that artificial neural networks draw an inspiration from 
neuro- and cognitive science, an artificial life approach to the problem 
could theoretically enlarge the field of investigation." (Calabretta /et 
al./, 1998 <http://laral.istc.cnr.it/rcalabretta/calabretta.modul3.pdf>)

*A general definition of modularity and nonmodularity in neural networks 
can be the following*: "modular systems can be defined as systems made 
up of structurally and/or functionally distinct parts. While non-modular 
systems are internally homogeneous, modular systems are segmented into 
modules, i.e., portions of a system having a structure and/or function 
different from the structure or function of other portions of the 
system. [...] In a /nonmodular/ architecture one and the same connection 
weight may be involved in two or more tasks. In a /modular/ architecture 
each weight is always involved in a single task: /Modules are sets of 
'proprietary' connections that are only used to accomplish a single 
task./" (Calabretta & Parisi 
<http://gral.ip.rm.cnr.it/rcalabretta/tedarwin/Altenberg.pdf>, 2005, 
Fig. 14.4; see also Calabretta /et al./, 2003 
<http://gral.ip.rm.cnr.it/rcalabretta/WhatDoesItTake.pdf>).

On 3/29/13 8:30 PM, Jeff Clune wrote:
> Hello Christos,
>
> Rafael Calabretta keeps a list of papers on the subject of the 
> evolution of modularity.
>
> http://gral.ip.rm.cnr.it/rcalabretta/modularity.html
>
> I like your idea of a wiki too. It could be a great resource for the 
> field. We could even start fleshing out this page, which is currently 
> nearly empty: http://en.wikipedia.org/wiki/Modularity_(biology) 
> <http://en.wikipedia.org/wiki/Modularity_%28biology%29>
>
> PS. Thanks to everyone who has participated in the discussion of our 
> paper The Evolutionary Origins of Modularity. Some of the papers that 
> have been mentioned we reference in our paper, and others are new to 
> us. We have enjoyed learning about the various different studies and 
> opinions on this subject, and look forward to more great work to come.
>
>
> Best regards,
> *Jeff Clune*
>
> Assistant Professor
> Computer Science
> University of Wyoming
> jeffclune at uwyo.edu <mailto:jeffclune at uwyo.edu>
> jeffclune.com
>
> On Mar 29, 2013, at 3:31 PM, Christos Dimitrakakis 
> <christos.dimitrakakis at gmail.com 
> <mailto:christos.dimitrakakis at gmail.com>> wrote:
>
>> Dear all,
>>
>> Is there no survey or taxonomy that discusses this line of work in one
>> place?
>> If not, I have a suggestion. Why not start up a wiki to begin with? That
>> would also be of tremendous aid to any newcomers.
>>
>> Best,
>> Christos
>>
>> -- 
>> Dr. Christos Dimitrakakis
>> http://lia.epfl.ch/People/dimitrak/
>>
>

-- 
--
Juyang (John) Weng, Professor
Department of Computer Science and Engineering
MSU Cognitive Science Program and MSU Neuroscience Program
428 S Shaw Ln Rm 3115
Michigan State University
East Lansing, MI 48824 USA
Tel: 517-353-4388
Fax: 517-432-1061
Email: weng at cse.msu.edu
URL: http://www.cse.msu.edu/~weng/
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