Sven Ebbesson and his colleagues at the University of Alaska in Fairbanks
studied the coho salmon (Oncorhychus kisutch), a short-lived species which
is plentiful in the seas off Alaska. They discovered that the brains of
the fish reorganise themselves just before the salmon head downstream.

The researchers found that when salmon are 18 months old, the part of
the brain responsible for scent, known as the olfactory bulb, expands by
about 70 per cent. The number of nerve cells in the olfactory bulb increases,
and some of the nerve fibres responsible for vision form new connections
to different parts of the brain.

The simplicity of the salmon brain makes it easy to detect changes in
the way in which nerve cells are connected, says Ebbesson. This makes it
possible to study the factors that turn these developmental processes on
and off. Ebbesson traces nerve pathways by injecting dyes into the brain
and mapping how they spread. In this way, he can identify different neurotransmitters
and their locations. In mammals, specialisation occurs in the embryo at
once, which makes it difficult to follow the sequence of events and the
factors that control development.

Ebbesson has identified a part of the salmon brain which is equivalent
to the mammalian neocortex. ‘It makes us realise that we share many parts
of the brain with lower vertebrates.’

Ebbesson feels that understanding nerve fibre growth of salmon may lead
to better ways of treating head and spinal chord injuries in humans.

The ship set out last May for a year-long voyage that was to circumnavigate
the globe. Had it succeeded, it would have been the first non-Soviet ship
to reach 90 degrees North. The ship was part of an international fleet
taking part in the International Arctic Ocean Expedition (IAOE).

Polar Star had completed less than one-third of its scientific work
when one of three propeller shafts broke down in the Arctic Ocean last month
and the vessel was forced to go south under reduced power. In the meantime,
less powerful Swedish and German icebreakers reached the Pole.

‘In the past we have been a prominent country in Arctic research,’ says
Susumu Honjo, of the Woods Hole Oceanographic Institution, and one of the
two chief scientists aboard the Polar Star. ‘But after this failure that
position is eroding rapidly.’

The main objective for the IAOE was to collect basic data for studies
of global warming. The Arctic Ocean plays a large part in determining the
climatic pattern of the northern hemisphere and an understanding of the
processes that occur in the ocean are essential in modelling climate change.
The ship was to have placed several automatic sensing stations which would
have downloaded data via satellite. The equipment would have measured 227
different elements, including the thickness of the ice, growth of plankton,
currents and meteorological conditions. The stations are expected to be
flown to the Pole next spring.

‘It’s an embarrassing tragedy,’ says Neal Thayer, chief of the Coast
Guard’s science branch, in ice operations. ‘The broken propeller shaft is
not the only thing we need to fix.’ Relations between the National Science
Foundation and the Coast Guard have been strained for some years. American
scientists wanting to work in the Arctic have complained about poor access
to ships that can work in the ice. They have come to depend entirely on
the Coast Guard, whose top priority is not scientific research. Both the
National Science Foundation and the Coast Guard have started to design new
icebreakers, but neither will be capable of reaching the North Pole.