Most natural smells are complex blends of many individual chemicals. Freshly ground coffee, for example, contains about 300 individual volatile components. A typical perfume also contains tens of ingredients, although the recipes are tightly locked in secret vaults.

The percepts that such complex blends evoke in us are, however, astonishingly singular: ground coffee smells like coffee, not like a hopeless mess of hundreds of ingredients; Gio or Allure also have unique signatures (often associated with other memories).

Function of a known pathway to memory in the brain is explained.

PASADENA, Calif. — A panel of experts who conduct a wide range of brain research will come together for California Institute of Technology's annual Biology Forum, "Gray Matters: Perception, Intention, Memory, and Dysfunction in the Brain," April 25 at 8 p.m. in Beckman Auditorium, 332 S. Michigan Ave, Pasadena.

Scientists at the California Institute of Technology and Purdue University have determined the fine-detail structure of the virus that causes dengue fever. This advance could lead to newer and more focused strategies for devising a vaccine to protect the world against a viral illness that causes 20,000 deaths each year.

Reporting in the March 8 issue of the journal Cell, Caltech biology professor James H. Strauss, lead author Richard J. Kuhn of Purdue (a former postdoctoral scholar in Strauss's lab), and Michael G. Rossman and Timothy S. Baker, both of Purdue, describe

Caltech researchers have blocked the effects of the disease in cultured cells using antibodies.

Using specially prepared HIV-derived viruses stripped of their disease-causing potential, California Institute of Technology biologist David Baltimore and his team have invented a new method of introducing foreign DNA into animals that could have wide-ranging applications in biotechnology and experimental biology.

The Baltimore team reports, on today's Science Express Web site, on their study of single-cell mouse embryos that have been virally infected in a manner that leaves a new gene from a jellyfish permanently deposited into their genomes.

Scientists at the California Institute of Technology have discovered that hearing can significantly change visual perception, and that the influence of hearing on visual perception occurs at an early perceptual level rather than at a higher cognitive level.

Ladan Shams, a Caltech postdoctoral researcher, and Shinsuke Shimojo, a professor of computation and neural systems at Caltech report that visual signals are influenced significantly by sounds at early cortical levels that have been believed to be "vision specific."

Caltech biology professor Barbara Wold has been appointed director of the Beckman Institute, President David Baltimore announced today. She succeeds founding director Harry Gray, who will return to full-time professorial duties after 15 years at the institute's helm.

Wold, who specializes in embryonic development and regeneration in vertebrates, will lead the Beckman Institute in its continuing goal of building a research interface between chemistry and biology, Baltimore said.

The California Institute of Technology has successfully completed a $111 million fundraising effort begun in 1998 to expand the biological sciences. The $111 million exceeds the original $100 million goal.

Funds raised during the Biological Sciences Initiative (BSI) will make possible a new building on the Pasadena campus, new professorships and fellowships, new faculty appointments, and a wide range of new research programs.

If you stare at a bright red disk for a time and then glance away, you'll soon see a green disk of the same size appear and then disappear. The perceived disk is known as an afterimage, and has long been thought to be an effect of the "bleaching" of photochemical pigments or adaptation of neurons in the retina and merely a part of the ocular machinery that makes vision possible.