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Honey Bee Forms Its Memory Through Smell

Team from the University of Cologne and the Free University of Berlin shows neuronal plasticity with imaging methods / publication in journal eNeuro

Honeybees can condition their memory performance through scents, which influences their behaviour. That is the result of a study on the honeybee’s associative learning and memory performance now published in the life science journal eNeuro. The article is co-authored by the zoologists and neurobiologists Martin Nawrot from the University of Cologne and Randolf Menzel from the Free University of Berlin. 

Nawrot explains that the honeybee’s short-term memory mainly works via scents that are processed in the so-called mushroom body, the animal’s olfactory learning centre. ‘Using high-resolution flourescence microscopy, we finally found out where the bee’s short-term memory is located’, says Nawrot.
But another result is even more significant according to the zoologist from the University of Cologne: ‘For the first time, we were able to measure how the connections between nerve cells change their plasticity in this part of the honeybee’s brain. And we were able to show something that has never been shown before: The more pronounced the change in plasticity after training with a certain scent was, the more reliably we observed the newly acquired behaviour in the bees. There is a clear correlation between the strength of a highly localized plasticity change in the brain and the animal’s learning success!’

The change in plasticity of the connection between nerve cells (synapses) is called neuronal plasticity and is an indicator for the bee’s learning level: The more often the stimulus goes from A to B and the animal is rewarded, the more strongly both points become connected through learning. This is called a memory trace. After training, a stimulus then automatically elicits the learned response. At the behavioural level, this is classical or Pavlovian conditioning (the dog and the bell).

In the honey bee study, the team of researchers from Cologne, Berlin and Japan conditioned the insects on different scents. Then, after being exposed to a scent the animal recognized or did not recognize, they measured whether or not the bee tried to get the expected reward (sugar water).
Nawrot explains his method: ‘The questions was: Will the bee stick out its proboscis or not? We tested this with several repetitions. If exposure to the scent was previously rewarded with sugar water, but another scent was not and the bee learned this, it stuck out its proboscis when smelling the previously rewarded scent, even if there was not sugar water. The scent that was not rewarded or an unfamiliar scent did not elicit this reaction. That way, we measured how well the animal learned and can access its memory.’

The results contribute to understanding the physiological foundations of memory formation in an insect brain. Protecting insects is currently also an important political aim. Nawrot sees some important connections to his research on honey bees: ‘Today, bees are exposed to may different pesticides with dangerous scents. Ideally, they can learn that these substances are harmful for them. Then they can remember and avoid them the next time. In the case of tastes, they already know when something they ate made them sick in the past.

Media Enquiries:
Professor Martin Nawrot
Zoological Institute at the University of Cologne
+49 221 470-7307

Press and Communications Team:
Frieda Berg
+49 221 470-1704