A Weizmann Institute-Brown University study has shown that object recognition by the human brain is far simpler than has been commonly thought, a finding that may facilitate the design of more effective vision-related systems, ranging from household robots to smart weapons.

Scientists have long been puzzled by the ability of the brain to reconstruct three-dimensional images from information conveyed by the two-dimensional retina. In a recently published study, Dr. Shimon Edelman of the Weizmann Institute's Department of Applied Mathematics and Computer Science and Prof. Heinrich Bulthoff of Brown University have determined that object recognition may be accomplished through a relatively simple process involving a comparison of two-dimensional views. Upon receiving input about an object, the brain compares its 2-D coordinates to a series of memorized "snapshots" of previously-seen objects. Recognition takes place when the brain, through interpolation, selects the "snapshots" that most closely approximate the new object.

In these studies, subjects were first shown computer images of a previously unseen 3-D object -- or "target" -- as viewed from various vantage points. The participants were then presented with single views of either the target or a "distractor" -- an object similar to but not identical to it. The researchers showed that the subjects could successfully identify the target only when its change in orientation was small enough for interpolation to take place, an indication that learned "snapshot" images and not mentally rotatable dimensional models underlie object recognition.

Funding for this research was provided by the U.S. Navy. Dr. Edelman holds the Elaine Blond Career Development Chair.

 

While it has been long known that an urchin spine is composed of a single crystal of calcite, the most common calcium-containing mineral, no one could explain why these crystals are so much more resistant to fracture than are calcite crystals from geologic formations or those grown in the laboratory. Prof. Lia Addadi, Prof. Stephen Weiner and Dr. Amir Berman of the Institute's Department of Structural Biology have now shown that this phenomenon is due, in part, to the entrapment of proteins within the crystal. In follow-up studies of these novel single-crystal composites by synchrotron X-ray radiation, this team -- together with Drs. Ake Kvick and Mitch Nelson of the Brookhaven National Laboratory in New York and Prof. Leslie Leiserowitz of the Institute's Department of Materials and Interfaces -- discovered how the entrapped proteins act to prevent cracks from spreading through urchin calcite. They found that laboratory-grown calcite crystals obtained from solutions containing proteins extracted from urchin spines had rodlike protein molecules integrated into planes oblique to the crystal cleavage planes, which would interfere with fracture propagation.

Their observations might eventually lead to the development of new single crystal-polymer composites that could be used to make less brittle materials. Continuing stages of this research are being supported by the United States-Israel Binational Science Foundation.

 

Israeli molecular biologists can now participate fully in the international quest to decipher the human genome, thanks to a $500,000 automated DNA Analysis Laboratory that opened last year at the Institute. The Human Genome Project, a 15-year multinational endeavor to sequence man's entire genetic storehouse, will make it possible to pinpoint the genetic origins of all five thousand human genetic diseases, hopefully leading to improved understanding of the function and formation of complex organs, including the brain.

Within the first six months of Laboratory operation, nearly all Institute molecular biologists had abandoned their own non-automated genetic sequencing procedures and started submitting samples to the new facility, which is part of the Institute's Biological Services Unit. Its expertise is also available to the wider Israeli scientific community.

According to Prof. Menachem Rubinstein of the Department of Molecular Genetics and Virology and Head of the Institute's Biological Services Unit, benefits have already been realized in Institute projects bearing on Down syndrome, human reproduction, the basis of odor detection, nerve repair and function, natural cancer protective mechanisms, and autoimmune diseases, among others.

DNA, the coded plan used by all living organisms to construct their various proteins, is a long chain-like molecule built from four different nucleotide bases tied together like a string of beads. The kingpin of the new Laboratory is a state-of-the-art DNA sequence analyzer, which accepts a gel loaded with as many as 36 different samples of specially prepared DNA and supplies a complete base sequence analysis in as little as eight hours.

Three other vital Laboratory components are soon to be added. One is a robot for liquid handling that will be able to automatically work up the DNA sample for insertion into the analyzer. The second component is a dedicated work station that will accumulate all data generated by the sequencer, reconstruct DNA chains too long to be handled by a single DNA analysis, and provide improved comparisons to known DNA sequences. The third instrument is a DNA fragment analyzer, which enables detection of genetic defects by separating, identifying and comparing large genetic segments.

Establishment of the automated sequencer facility was initiated by the Institute's Human Genome Committee, which supervises the Laboratory's integration into DNA-sequencing activities elsewhere. Its members are Profs. David Givol, Yoram Groner, Doron Lancet and Menachem Rubinstein. Equipping the Laboratory was made possible by a contribution from the Forchheimer Foundation and grants from the Planning and Budgeting Committee of the Israel Council for Higher Education and the Wolfson Family Charitable Trust.