Bees are no bird-brains
9 December 2003 14:00 GMT
by Henry Nicholls

When it comes to judging cognitive ability, neuroscientists are guilty of
prejudice against invertebrates, argues an expert in honeybee cognition. Bee
brains are capable of much more than is assumed, he claims.

"We have this kind of prejudice that insects or invertebrates are
essentially stupid," said Martin Giurfa, a neuroethologist at the Center for
Research on Animal Cognition in Toulouse, France. Because of this,
researchers are failing to ask the right questions of invertebrates, he
says. But the cognitive abilities of the honeybee, one of the best studied
insects, are showing that insects and possibly other invertebrates can
perform some quite advanced mental tasks.

The current cognitive champion of the invertebrate world is the honeybee,
says Giurfa. With fewer than a million neurons and a volume of just 1 mm3,
the honeybee brain has "well developed learning and memory capabilities,
whose essential mechanisms do not differ drastically from those of
vertebrates," he notes in a special issue of Current Opinion in Neurobiology.

For example, a complex odor comprised of several compounds triggers neural
correlates of each of the separate elements that make up the smell, says
Giurfa. But there is also "a special kind of signature for this and only
this mixture that could tell the brain that there is something more than
just the elements," he said. "It is clear that something is going on in the
mini brain of the honeybee that is more than just a sum of the stimuli."

A common explanation for the advanced nature of the honeybee brain is that
selection imposed by the need to be social has driven the evolution of the
insect's nervous system.

But Giurfa says that the level of cognition found in the honeybee need not
be restricted to social insects. "I think that it's not that invertebrates
are stupid or the honey bee brain is unique, it's that we haven't raised
these kinds of questions yet in other kinds of invertebrate models."

For instance, he says, although Drosophila have traditionally been
considered "stupid," not only is the fruit fly capable of contextual
learning, attributing a different meaning to the same stimulus if
encountered in a different context, it can also show selective attention,
picking which of several stimuli it wants to respond to. This, in
particular, is assumed to be a property found only in highly developed
vertebrates, he says.

Recently, Bruno van Swinderen and Ralph Greenspan, behavioral geneticists at
the Neurosciences Institute in San Diego, California, carried out selective
attention experiments on Drosophila. "A fly sitting on your tablecloth is
not just a bag of reflexes waiting for something to happen," explained van
Swinderen. "It's actively looking at you, then the wineglass, then the fork,
then you again."

This, he says, is fundamental to how a fly learns and to how it builds a
salience map, a two-dimensional, topographically organized map that reflects
the distinctiveness of objects around it. "As such, that's probably not so
different from the way our brains work, except that the complexity of
salience maps is probably much smaller," van Swinderen told BioMedNet News.
This suggests that even Drosophila have a mind of sorts, he concludes.

Greenspan, who worked with van Swinderen on the study, agrees. "The
traditional reluctance to attribute such faculties to insects derives, to a
large extent, from the failure to ask them the right questions," he said.

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