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Neurobiology and the Behavior of the Honeybee 
When
animals and humans learn, the neural circuits in the brain change, thus
establishing a memory trace. This
allows the individual to better control its behavior in the future. The
difficulty in locating memory within the gridwork of many thousands of neurons
is due to the fact that the neurons involved in learning cannot be directly
observed while they create the memory trace. It is therefore advantageous to
study a relatively simple nerve system, which is however still able to learn
quickly and form multiple memory traces including that of a stable long-term
memory. We investigate this topic using the honeybee. Bees learn
landmarks in order to navigate within their territory. They associate the odors, colors, shapes and locations of flowers which
offer nectar and pollen. They
learn from each other when they perform the waggle dance to indicate the
direction and the distance of rich feeding spots or a new nest. In
doing so, their learning behavior is remarkably elaborate. They generalize on the basis of the common visual characteristics of
visual patterns (e.g. symmetry or asymmetry), and they adjust their decision
according to perceived signals or the situation in which they find themselves.
Especially important for us as
neuroscientists is the fact that bees can learn when optical and electrical
recordings are being made in their brains. In these situations, an odor is used as a stimulus for a sugar reward,
and the animals learns, just as Pavlov’s dog did, to expect the reward after
experiencing the stimulus. This
makes it possible to search for the locations where memory is formed and to
measure the changes in the neuronal circuits. We can, for example, find that
an odor that was learned as an important one has a stronger and
more precise neuronal representation in the brain than other odors. These memory traces can be tracked all the way to the individual, identified
neurons and their circuitry. This opens up the possibility of detecting the
crucial elements which establish the memory trace in the bee’s brain.
A
unique feature of memory is its dynamic aspect, a characteristic which the
bee’s memory shares with the memories of humans and many animals. This
means that a sensitive short-term memory phase follows the learning experience,
in which memory can be easily changed or impaired. In the next phase, a mid-term memory can direct behavior for several
hours after learning; the following phase is long-term memory, which, in bees,
is divided into an early (1 - 2 days) and a late (more than 2 days) long-term
memory.
We found that the memory phases are directly related to
specific reaction chains of signal molecules in the neurons involved in
establishing that memory. Certain enyzmes (protein kinases) play a key role;
their activation leads to a functional change in existing molecules and later
to synthesis of new proteins, thereby creating new structures. The cellular
reaction paths that become active here are nothing special; they are present
in almost all the cells in the body. They are also not specific to the
honeybee; they are found in the cellular mechanisms of the memory trace in
other animals, from snails to humans. The memory content is not stored in
certain special molecules, rather, it is retained in the pattern of the
changes in the circuitry created by the common molecules. This principle of memory retention is also present in humans, therefore
the bee brain can be used as a model system for studying the general
mechanisms of memory formation. Observing the temporal dynamics of memory
traces, we find vast differences among different animals. These dynamics seem
to be coupled with the behavioral conditions in which memory is used. We can
show that in bees the food-gathering cycle is closely aligned to the temporal
dynamics of the memories used in foraging.
Topics and projects for Bachelor or Master Thesis / Themen und Projekte für
Bachelor- und Masterarbeiten
C.V. Randolf Menzel
Publications by the Menzel group
MNU Vortrag Berlin im September 2012 (Navigation und Kommunikation)
Our current research projects on honeybees are:
-
Molecular biology of sensory perception and synaptic plasticity
in the honeybee
Leboulle
- Neural correlates of olfactory coding and learning:
Electrophysiology
Bartels /
Zwaka
/ Menzel
- Navigation in honeybees: the organization of large-scale spatial memory
Menzel /
Greggers
/ Jin
/ Kirbach /
Degen
/
Miehe
- Visual systems and the ecology of floral patterns
Menzel
- Elementary and configural
forms of olfactory and visual conditioning
Menzel
- Neuronal
correlates of olfactory coding and learning: Optophysiology
Chakroborty / Menzel
- Structure and plasticity of the olfactory pathway
Rybak (freier
Mitarbeiter) / Menzel
- Sleep and its role in memory consoliation
Menzel
- The Honeybee Standard Brain Atlas
Rybak
(freier Mitarbeiter)
/ Menzel
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