Work at the University of New England is opening a new window onto the world of memory in the honeybee.
Experiments conducted by UNE’s Emeritus Professor Lesley Rogers and Professor Giorgio Vallortigara from the University of Trento, Italy, have revealed an impressive complexity in the way bees store and retrieve their memories of odours.
Recruiting subjects from the grevillea bush flowering at Professor Rogers’s laboratory door, the scientists trained them to associate a lemon scent with a reward of sugar. Bees “smell” with their two antennae and “drink” with their proboscis, and they quickly learn to extend their proboscis (the so-called “proboscis extension reflex”) in response to an odour they associate with a sugar reward â€“ even in the absence of that reward.
Professor Rogers and Professor Vallortigara are international authorities on the specialised use of the left and right sides of the brain in many aspects of cognition and behaviour. Professor Rogers is a pioneer of research that, over the past 30 years, has shown that such specialisation â€“ once thought to be unique to humans â€“ is widespread among vertebrate species.
This research is now revealing comparable “lateralization” in the much smaller brains of invertebrates, including the finding that bees learn to associate odours with rewards more efficiently when using the right antenna than when using the left. The UNE experiments were designed to track this lateralised response along the surprisingly intricate corridors of the bee’s memory.
Using the evidence of the “proboscis extension reflex”, the researchers found that, initially, bees remembered the reward associated with the lemon scent when the scent was presented to their right antenna but not when it was presented to their left antenna. After six hours, however, this memory was recalled only when using the left antenna. This could be shown simply by presenting a droplet with the odour on the left or right side of the bee.
“While we don’t yet know whether it’s the memory site itself or the recall pathway that ‘shifts’ during this period,” Professor Rogers said, “this result corresponds to findings in vertebrates showing that long-term and short-term memories are stored in different parts of the brain.
“This shift from one antenna to the other may allow the bee to learn new scents of nectar-giving flowers, using the right antenna, without interference from older memories. Such lateralization seems to be a necessary – or advantageous – feature of any brain with paired sensory organs, regardless of its size.”
Professor Vallortigara is Director of the Centre for Mind/Brain Sciences at the University of Trento, and also an Adjunct Professor at UNE. This research was begun when he visited UNE’s Centre for Neuroscience and Animal Behaviour on a Faculty Distinguished Visitor Award in 2007.
The paper reporting on the research will be published today in PLoS ONE, the journal of the Public Library of Science. Read the article online at http://www.plosone.org/doi/pone.0002340.
For more information contact Emeritus Professor Lesley Rogers on (02) 6773 3969 or Jim Scanlan on (02) 6773 3049.