REVIEW Learning in honeybees: from molecules to behaviour**

Studies in a variety of organisms as diverse as molluscs, insects, birds and mammals have shown that memories can exist in a variety of temporal domains ranging from short-term memories in the range of minutes to long-term memories lasting a lifetime. While transient covalent modifications of proteins underlie short-term memory, the formation of long-term memory requires gene expression and pro-tein synthesis. Different intracellular signalling cascades have been implicated in distinct aspects of learning and memory formation. Little is known however, about how learning in intact animals is related to the modulation of these signalling cascades and how this contributes to distinct neuronal and behavioural changes in vivo. Associative learning in the honeybee provides the opportunity to study processes of memory formation by analysing its progression through different phases, across levels of behaviour, neural circuits, and cellular signalling pathways. The findings reveal evidence that various cellular signalling pathways in the neuronal circuit of distinct brain areas play a role in different processes during learning and memory formation. Key words: antennal lobes, associative learning, memory, protein kinases, second messenger cascades Drosophila mutants. The mutants dunce and rutabaga with defects in associative learning also have defects in enzymes regulating the cAMP level (for reviews see Davis, 1996; Dubnau and Tully, 1998). The cAMP/PKA cascade’s role in learning and memory formation has been confirmed by investigations addressing the role of PKA and cAMP-responsive transcription (Davis,1993, 1996; Dubnau and Tully, 1998; Yin and Tully, 1996), providing convincing evidence that the cAMP/PKA pathway plays a key role in the formation of LTM. At about the same time, the cAMP/PKA pathway’s role in formation of long-lasting neuronal changes has been demonstrated for the marine snail Aplysia. Here, the in-duction of synaptic long-term facilitation (LTF), a cel-lular analogue of a defensive withdrawal reflex, re-quires the cAMP-mediated processes (Byrne and Kan-del, 1996; Carew, 1996). The fact that the cAMP is als