Science: Update

SHORT-TERM and long-term memories are distinctly different states of mind, a finding that raises the prospect of developing smart drugs to help victims of senile dementia.

Remembering events over a short period of time involves quite separate chemistry in the brain to that needed for storing long-term memory, according to a study by a Brazilian team of scientists led by Ivan Izquierdo, a neuroscientist from the Federal University of Rio Grande do Sul.

In experiments on lab animals the researchers were able to block short- term memory with drugs that had no effect on long-term memory.

Scientists want to work out how short-term memories are transferred into the long-term databanks of the brain in order to develop smart drugs that can help the process.

Professor Steven Rose, a memory researcher at the Open University, who is collaborating with the Brazilian team, said that such drugs will help to improve the lives of Alzheimer's patients in the early stages. ``It will not, however, stop the decline as that needs a more fundamental approach," Professor Rose said.

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ASTRONOMERS HAVE been surprised to discover that global warming affects Triton, the icy moon of Neptune. Triton is approaching the position where it is nearest to the Sun, so its nitrogen-rich polar ice fields should evaporate. However, Jim Elliot of the Massachusetts Institute of Technology used the Hubble Space Telescope to show that Triton's atmosphere is warming faster than anyone predicted. This was discovered by studying light from a distant star as Triton passed in front of it - a neat way of measuring temperature without thermometers.

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MEANWHILE ANOTHER group of neuroscientists believe they have identified a site in the lower back of the brain that perceives colour. In rare cases, people lose that ability because of brain damage, so what they see looks similar to the pictures of a black-and-white television.

Researchers have been trying to identify the site within the area of damage that is responsible for colour perception. In the new study, they showed displays of colour and black-and-white images to 13 healthy people while scanning their brains to detect those regions that responded to the colour. The work led them to implicate a small site they call area V8. The results are reported in the July issue of the journal Nature Neuroscience by Dr. Nouchine Hadjikhani and colleagues at Massachusetts General Hospital's Nuclear Magnetic Resonance Centre.