Fearlessness can be learned

Whistling a happy tune may be the answer for some but for others there is no way to avoid deep-seated fear in stressful situations. The result can be post-traumatic stress syndrome or depression. Now Professor Eric Kandel, the Nobel Prize-winning neurobiologist, and his group at the Howard Hughes Medical Institute say it may be possible to learn not to be afraid, a condition he calls "learned safety".

The process, which he describes as "a bit like psychotherapy", leads to changes in the brain, especially in the amygdala, the brain's fear centre, and suggests new possibilities for the development of anti-depressant drugs.

In Prof Kandel's experiments, mice learned to associate both safety and danger with specific sounds. Mice conditioned to safety in stressful situations, such as being forced to swim, were able to overcome the "sense of hopelessness" that engulfed non-conditioned mice. The conditioning process, he argues in the journal Neuron this week, is as effective as the anti-depressant Prozac. "I've always been interested in psychotherapy," he said. "Since it is a learning experience, there must be a biological basis in the brain." His research shows it is.

Volcanoes prove unpredictable

Hopes that it may be possible to predict the behaviour of volcanoes with greater accuracy have been dashed by teams of US and UK scientists, who have discovered that eruptions are more complex than previously thought.

The scientists, from Penn State and the University of Arkansas in the US and the University of East Anglia in the UK, have been analysing data from the Soufrière Hills volcano, which has been erupting on the Caribbean island of Montserrat since 1955. Their principal finding, detailed in the journal Science on Friday, is that pressurised magma - molten rock and gas which becomes lava at the surface - continually recharges the volcano from a number of chambers causing episodic eruptions at the surface. Previously it was thought that magma was contained in a single chamber or reservoir at the heart of the volcano prior to emission, making it possible to predict the course and duration of the eruption.

Bacterium thrives in own ecosystem

A bacterium, Desulforudis audaxviator, has been discovered living in solitary splendour 2.8km below the surface of the Earth with neither light nor oxygen and at temperatures of 60°C. It is thought to be the first ecosystem ever found sustaining only a single living species.

The rod-shaped organism and its mode of life - it gets its energy from hydrogen and sulphates produced by the radioactive decay of uranium - hint at the kind of forms of life which might be detected on other planets.

The bacterium's genetic material contains everything the organism needs for a solitary existence. Its discovery in the Mponeng gold mine, South Africa, is reported in Science on Friday.

Dylan Chivian of Lawrence Berkeley National Laboratory in California, the lead author, said the discovery proved other planets could support life independently without access even to the sun.