From: tychay@juliet.caltech.edu (Chay, Terrence Y.)
Newsgroups: alt.cyberpunk.tech
Subject: Re: n-Dimensional Cyber Space
Date: 9 Sep 92 07:36:00 GMT
Organization: California Institute of Technology
News-Software: VAX/VMS VNEWS 1.41

Norman Oursland (naoursla@eos.ncsu.edu) writes...
  The above information is based on experiments where researchers 
  gave primates a "dye" that would show up on a type of scanner (they use the
  same stuff on people for certain medical tests. I understand it's like drink-
  ing chalk). They then showed them pictures with black and white patterns on 
  the Imaging of the blood flow in their brains matched the patterns they show
  the subjects.

@Man (shaun@octel.com) writes... 
  I think you are misinterpreting or misremembering this experiment.  If you 
  could post a reference, I'd approach the limit of gratefulness.  :)

----
  some staining techs that i remember

CYTOCHROME OXIDASE
  a mitochondrial dye (i think). thus
dark patches represent heightened enzymic activity (Kandel & Shwartz _Principles
of Neural Science).  This was used to find the "blob" and "interblob" regions
in the primary visual cortex (V1).  interblob regions have orientation 
selectivity whule blob regions have the "color channel".  there are other
differences but i can't recall them.

NISSL STAIN
  and i quote (again from Kandel and Schwartz)
  Within a few days following axotomy [injury or severing of axon], changes 
occur in the cell body of most types of neurons,  For example, the cell body
of a dorsal root gangloins cell or spinal motor neuron swells, and may even
double in size... Next, the rouch endoplasmic reticulum breaks apart and moves
to the swollen cell body.  This pheomenon, referred to as -chromatolysis-, is
useful histological [post-mortem] indication that the axon of a neuron has
been severed.  Chromatolysis can be most easily seen when the rough endoplasmic
reticulum is stained with basic dyesm such as thionin, that bind to the 
ribosomes.  After injury, endoplasmic reticulum that is stained in this way
(termed -Nissl substance-) can be seen around the margin of the cell around
the nucleus as in uninjured cells.
  i think they use this in lesion experiments then agin maybe not.

Injection of TRITIATED PROLENE AND FUCOSE
  was injected into an eye and the radioctive material is transported by the
Lateral Geniculated Nucleus (LGN) to V1.  performing a postmortem autoradiograph
on sections of the brain, will yield white parts (connected to that eye via
LGN) and black (not connected).  reference is Hubel and Wiesel (of course)

2-DEOXYGLUCOSE
  *OH, BABY. I THINK THIS IS THE ONE WE ARE TALKING ABOUT*
  glucose analog that can be radiolabeled and injected into brain.  Cells that
are metabolically active take up the label and can then be detected in sections
of cortex overtaid with X-ray film.  Thus, when a stimulus of lines with a given
orientation is presented an orderly array of active and inactive stripes of 
cells is revealed.  Kandel & Shwartz (again!)

AND AGAIN from Kandel and Schwartz
 A remarkable advance now allows the different columns to be visualized 
directly in the living cortex.  Using either a voltage-sensitive dye or 
inherent differences in the light scattereing of active and inactive cells, a
highly sensitive camera can detect the pattern of active and inactive 
orientation column during presentation of a bar of light with a specific
axis of orientation.

----
As for the 3-D N-D thing
  an excellent 2-Deoxyglucose stain was done using concentric circle/radial
line stimulus by Tootel Silverman, Switkes & RL De Valois in _Science_
218:902-904.  Of course, i didn't read it there but in _Spatial Vision_
by RL De Valois and KK DeValois.  it's pretty impressive.
  basically, the primary visual cortex has a log-polar map of the visual field
(very rough of course).  Possibly useful for size- and rotation- invariant
representations of objects, as well as transformation in size or rotation will
be simple shifts in cartesian coordinates on a log-polar map.  ("Computational
Anatomy and Functional Architecture of Striate Cortex: A Spatial Mapping
Approach to Perceptual Coding" by Eric L Schwartz in _Vision Research_
20:645-669.  There may be other reasons for this mapping dealing with
simplifying motion processing.
  i don't know what this implies for N-D reps but i hope this helps, and
its the closest thing to what Mr. Oursland was talking about.

------
as for the fourth dimension (time)
  we all know that time has a different geometry than space (in Special 
Relativity).  The best representation of this that I've seen was in the
physics program _The Mechanical Universe_ produced at Caltech.  The animation
was done by Jim Blinn of JPL (i think).  of course, that only involved 2-D
(one space and one time).

-------
 btw, i'm no neuroscientist so i could be full of it.  if you don't believe
me look it up.  i've heard that there is this primitive service called a 
"library" still in existence and there you can check out books for free!

          terrychay
                 TYCHAY@CITJULIE.BITNET
                 tychay@juliet.caltech.edu
Newsgroups: alt.cyberpunk.tech