Nina Müller-Deisig   Freie Universität Berlin  Institut für Biologie  - Neurobiologie -  Königin-Luise-Str. 28-30 14195 Berlin / Germany   phone:  ++49 30/838-56448  e-mail: ninamd@neurobiologie.fu-berlin.de

A concept of symmetry in an insect (Apis mellifera)

Honeybees discriminate bilateral symmetric from asymmetric stimuli and transfer such a discrimination to novel stimuli. These results demonstrate that bees categorize stimuli on the basis of their symmetry but not that they possess a concept of symmetry. Reversal experiments, in which the previously non-reinforced feature is rewarded, are critical to detect whether animals handle a set of features as an unique concept.

To test whether bees possess a concept of symmetry, they were trained to categorize either novel symmetric or asymmetric stimuli. They were afterwards trained in a reversal schedule (i.e. they were rewarded on asymmetric stimuli if previously rewarded on symmetric ones and vice versa). Bees switched immediately to the previously non-rewarded stimuli, thus showing that symmetry and asymmetry do not need to be learned separately but constitute complementary aspects of the same information. In control experiments, bees were first trained to categorize stimuli on the basis of their degree of disruption. Afterwards, they were trained to categorize stimuli on the basis of their symmetry. These bees did not show a rapid learning of the symmetry/asymmetry information in the second phase. Thus, the immediate switch towards the alternative information observed in the reversal symmetry/asymmetry was a consequence of having learned one of these features in the first phase of the experiment. We conclude that honeybees possess a concept of symmetry because they learn symmetry as a complement of asymmetry and vice versa. This work constituted my Diplom work done under the direction of Dr. Martin Giurfa.

Publications:

Giurfa, M.; Hammer,M.; Stach,S.; Stollhoff,N.; Müller-Deisig,N. & Mizyrychi,C. (1998) Pattern learning by honeybees: conditioning procedure and recognition strategy. Animal Behaviour 56:315-124 

Poster on the 5^th Int. Congress of Neuroethology: "Symmetry perception in an insect" 

Present projects and PhD-Thesis

The aim of my PhD thesis is to determine which mechanisms underlie the formation of a prominent structure of the insect brain, the mushroom bodies and to study the functional relevance of the mushroom bodies for the adult animal. The mushroom bodies (MB) of the honeybee, Apis mellifera, are considered centres of higher multisensory integration. They were also suggested to play a major role in learning and memory. By means of ablation experiments (see Malun, Giurfa), I will analyse the role of these structures in higher-order learning processes. In particular, intact and mushroom-body ablated bees will be tested in configural and elementary paradigms. Associative and non-associative learning will also be studied in both kinds of bees. 

The following questions should be examined: 

- is the multimodal sensory integration a basic function of the mushroom bodies ? 

- are the mushroom bodies essential for configural associations ? 

- are the mushroom bodies essential for spatial learning ?

last updated March 3, 2000