You can teach an old owl new tricks

HEMAI PARTHASARATHY

Owls hold sight and sound maps in a brain region called the tectum. © Anne Knudsen & Melanie Ciferri

Concerned that your learning days are done? Don't despair - a new owl study hints that adult brains can adapt to change, as long as it is incremental.

Brie Linkenhoker and Eric Knudsen of Stanford University School of Medicine in California have developed a step-by-step training programme that enables adult laboratory owls to adjust to wearing prism glasses that alters what they see so that it does not fit with what they hear.

Little by little, adult owls re-chart their mental maps of sound space to square with the bizarre visual changes they face¹. Neuroscientists had thought that this aspect of birds' brains was set forever once their youthful development was complete.

Patience, it seems, is the key to teaching old animals new tricks.

An owl whose survival depends on catching its prey may display an even greater capacity for change. Systems that make the brain more flexible may kick in during arousing activities such as hunting.

Critical faculties

The age at which a child learns a first language or a duckling identifies its mother are 'critical periods' in brain development: if you don't learn the skill then, you never will. Scientists think that this is because as the brain develops, certain circuits are set up to be less malleable, and thus more robust, than they are in youth.

In 1989, using prism glasses, Knudsen's laboratory identified a critical period in barn owl development². During the first months of an owl's life, the researchers showed, a brain region called the tectum coordinates the bird's exquisitely accurate map of visual space, with a similarly acute notion of its auditory environment.

This synthesis enables an owl to identify a mouse and its squeak as coming from the same place in the dead of night.

Now Linkenhoker and Knudsen show that older owls also have plasticity in the tectum. First the duo fitted the owls with prismatic glasses that caused small visual shifts. They allowed the birds' brain maps to respond to these before imposing greater ones.

Using this gradual approach, they saw much greater changes in the adult birds' brains than when they tried to shift the animals' visual world all at once. The brain plasticity of older owls was still no match for that of younger birds, however.

1. Linkenhoker, B.A., Knudsen, E.I. Incremental training increases the plasticity of the auditory space map in adult barn owls. Nature, 419, 293 - 296, (2002). |Article|
2. Knudsen, E.I. & Knudsen, P. F. J. Neurosci, 9, 3297 - 3305, (1989). |Article|

© Nature News Service / Macmillan Magazines Ltd 2003