Olaf Sporns: Connectivity, Dynamics, and Embodiment
<p>May 08, 2011 08:50 PM
 
O Sporns talk at the Brain Dynamics Conference in 2007 January...  at Walter Freeman's 80th birthday.
 
he says he first heard a radio talk abt work of Walter F and Karl Pribram when Olaf was in high school
in 1980;
 
v good English  (German)  Tubingen PhD
 
Olaf  101 neurons and 1015 connex.
wiring total length 100,000 miles
 
Emergence:  irreducible phenomena...
 
brain is embedded in body and in environment;
 
Anatomical  = structural connectivity
 
Functional connectivity:  network of causal effects  patterns of statist coneectivity
 
Effective connectivity  netowkr of causal effects,  combo of functiona and structural
 
mesoscopic  (middle)  within and btwn microcolumns (minicolumns) or other loca  cell assemblies
 
David Van Essen 1991   36 or so segregated regions in macaque visual cortex
(I shud pay David  a royalty every time I show this)
 
Social scientists look at networks for decades... hubs, small world... done this in 1970s.
transportation, social networks, food webs (ecology), proteomics
 
I want to steal methods from them.  neurosci is not in the lead;
 
distance btwn 2 vertices is the length of the shortest path;
 
digraph = directed graph;  clustgerin coefficient  (how many of your friends are friends of each other)
 
1998  Small World Networks  Watts and Strogatz Nature 1998  most cited paper;
 
Small world = short path length and high clustering....  short path to everything (6 degree eg);
 
Anatomic networks are small world...
 
only 13 elementary subgraphs  (of digraphs)  min  22:10  network bldg blocks
 
26 minute:  want to most damage... take out the HUB (if you're Jack Bower)
where are the HUBS in macaque in CoCoMac  V4 is highest  communicates with tempr and dorsal visual areas;
high centrality;  FEF;  area 46; area 5  other central areas.
 
segreagation is rel. to clustering coeffic
and integration = path length;
 
min 35:  Granger causality  functional causality
 
min 38  small world connectivty and complex dynamics  (put things on a sphere.... no boundary problems)
learned from Eugene)  Wilson Cowan dynamics
 
with random connex get low complexity and just  epileptic fits....
 
but with small world,,,,  get beautiful dynamics  .... great demo on sphere  at minute 40;
 
Small World and cortical dynamics also does this....
Charlie Grey  1990 post-doc  synchronization...
 
get a nice  image of moving diamond against background... min 42...
 
min 49  Hubs are context dependent  (even something like V4  waxes and wanes in centrality)
 
movie by Karl Sims  <a href="http://www.biota.org">www.biota.org</a>....  tried to evolve structures that locomote thru water or
surface   stunning video!!!!!
 
brains have always evolved with bodies in an environment.
 
George Buzsaki....   if u only use gaba (did he mean glutamate)
 and excitat u do NOT get beautiful dynamics...
 
walter freeman: power law is ubiquitous in connex....=> scale free;
 
 
u must have subcortical circuits.
 
 
 
 
 
 
 
 
 
 
 
 
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