[Comp-neuro] Re: (1) Maybe channel biophysics is not the "real" level for analysis of brain function.

james bower bower at uthscsa.edu
Fri Aug 22 00:30:33 CEST 2008


and nice to have engaged you again in this debate as well -- ah the  
old days -- anyway. Just one technical point (perhaps to make a larger  


As you know, PSTHs are a statistical device derived from point process  
statistics whose central assumption is stationarity, thus your  
carefully added caveat " sometimes get approximate statistical  
consistency this way, sometimes not. "  A second assumption, the  
points (or action potentials) occur completely independent from each  
other as independent samples of the underlying process.

So, how appropriate really is this statistics to a device whose  
dynamical behavior is "held in the biochemical states of its neurons,  
developed through environmental experience, as they behave in complex,  
dynamically shifting networks."  And how much is this a leap of faith?

Which leads me to the following bit of history -- as a postdoc, I  
developed a technique (in Llinas' lab) to record from multiple (32)  
cerebellar climbing fibers at once -- I took that data to Wisconsin  
and to a wonderful mathematician named Josh Chover, and asked him how  
the heck to analyze this data.  He and I ended up teaching a course  
(in 1982) on multi-neuron data analysis (A guy named Matt Wilson was  
the TA).  During the course,   i realized that not only PSTHs but also  
correlation analysis (still the mainstay of this type of data  
presentation), was completely inappropriate - Despite taking multiple  
statistical courses as an undergraduate, I also finally realized the  
critical connection between the assumptions of the model from which  
any particular statistics is constructed (point process statistics) ,  
and the organization of the system to which they were applied  
(neuronal firing patterns).  Faced with the realization that point  
process statistics was completely inappropriate to analyze neuronal  
firing patterns - I asked myself, "what is the appropriate model from  
which to extract statistics to study the brain?" -- I decided that, in  
the limit, that model was the brain itself -- which is the original  
origin of my interest in building realistic models.  I convinced Matt  
Wilson to build a model of the olfactory cortex (over my supervisor  
Lew Haberly's objections), Matt came to Caltech where I bullied him  
into building the framework for GENESIS (to which he has never  
returned) -- and the rest, as they say is (if we are lucky) history.

So, I actually believe that the process of building analytical  
infrastructure around realistic models, is really the process of  
building statistical devices to keep shaping the models based on  
biological data.  And, I am suspicious of any level of modeling or  
analysis that relies on more generalized statistical models (like  
point process statistics).



Dr. James M. Bower Ph.D.

Professor of Computational Neuroscience

Research Imaging Center
University of Texas Health Science Center -
-  San Antonio
8403 Floyd Curl Drive
San Antonio Texas  78284-6240

Main Number:  210- 567-8100
Fax: 210 567-8152
Mobile:  210-382-0553

The contents of this email and any attachments to it may be privileged  
contain privileged and confidential information. This information is  
for the viewing or use of the intended recipient. If you have received  
e-mail in error or are not the intended recipient, you are hereby  
that any disclosure, copying, distribution or use of, or the taking of  
action in reliance upon, any of the information contained in this e- 
mail, or
any of the attachments to this e-mail, is strictly prohibited and that  
e-mail and all of the attachments to this e-mail, if any, must be
immediately returned to the sender or destroyed and, in either case,  
e-mail and all attachments to this e-mail must be immediately deleted  
your computer without making any copies hereof and any and all hard  
made must be destroyed. If you have received this e-mail in error,  
notify the sender by e-mail immediately.

More information about the Comp-neuro mailing list