Unveiling the Secrets of Thinking - Carl Zeiss

Cover Story: (Re)solution
years to record the brain
of a mouse, not to
mention the mapping
of the human thinking
apparatus.
A puzzle with many facets.
Even the initial
preparation of a brain
section is no easy matter.
The material is subsequently
embedded in synthetic resin
and cut with a microtome,
a type of planing device, into
wafer-thin slices that are applied
to a wafer and imaged in a
scanning electron microscope. Such a
specimen has a volume of about one
cubic millimeter; this cube is cut up
into about 20,000 slices. Vast processing
times are required to subsequently
merge the resulting huge
quantities of image data into a
three-dimensional image in the computer
again.
Speed means success. Carl Zeiss is
supporting this research work with
intelligent solutions. With the aid of
the SIGMA TM field emission scanning
electron microscope (FE-SEM), biologist
Jeff Lichtman from Harvard University
in Cambridge, Massachusetts,
is examining pieces of a mouse’s
brain. The system is equipped with a
special detector system and software
that allow 100 times faster image
generation and storage than with
traditional systems. For John Mendenhall
of the University of Texas in
Austin, speed is an important argument
in favor of using a ZEISS FE-
SEM. Together with a special application
solution, the system has an
image memory with a capacity of up
to one gigapixel and therefore permits
the recording of large-area
specimens at maximum resolution.
Dr. Marco Cantoni of the Ecole Polytechnique
Fédérale de Lausanne in
Switzerland examines mouse brains
with a CrossBeam ® microscope. Instead
of a mechanical technique, an
ion beam is used to remove the specimen
slice by slice, with the result
then being examined in the scanning
electron microscope. This process
is largely automated. “The result
was incredible. In 48 hours we
generated 1600 images of specimen
slices, each with a thickness of just
six nanometers,” explains Dr. Cantoni.
“This gives us an insight into the
three-dimensional structure of the
tissue to be examined.” The ORION ®
helium ion microscope also offers
possible applications in the field of
brain mapping. The potential of this
technology lies, above all, in its extremely
large depth of field and the
innovative contrast mechanisms offered
by imaging with ions.
Brain research as an industry. The
quest for images and data already
shows that this scientific challenge
cannot be mastered without broadbased
research. The opinion is now
increasingly being voiced that Connectome
research should be industrialized,
much like the situation with
genome research at the end of the
last century. The solution could be
that entire “farms” will emerge
comprising dozens of electron microscope
systems in which brain sections
will be imaged day and night.
The computer industry is also faced
with a major challenge. Its job will
be to create gigantic storage media.
Even one cubic millimeter of mouse
brain delivers information totaling
1000 terabytes; this would be one
million times 1000 terabytes for the
human brain.
However, knowing the circuit diagram
still does not allow any deductions
to be made about the activities
of the thinking machine. The
question as to the effect that a nerve
cell really has on its direct surroundings
remains unresolved for the
time being.
Monika Etspüler
Innovation 22, 9 / 2010
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