Morphological Analysis of Kenyon Cells of the Drosophila Mushroom Bodies
Vasmer, David
Doctoral thesis
Date of Examination:
2016-12-21
Date of issue:
2017-01-18
Advisor:
Fiala, André Prof. Dr.
Referee:
Fiala, André Prof. Dr.
Referee:
Göpfert, Martin Prof. Dr.
Persistent Address: http://hdl.handle.net/11858/00-1735-0000-002B-7D18-7
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Abstract
English
Learning and memory is an adaptive behavioral trait that allows animals to make predictions about their environment based on previous experiences. Fruit flies that commonly use olfactory cues to locate food sources or mating partners, are able to assign value to odors after classical conditioning. The trace of the olfactory associative memory could successfully be localized to the Drosophila mushroom bodies, a central arthropod brain structure. The mushroom body intrinsic Kenyon cells are believed to store the memory in the synaptic connection to mushroom body output neurons. To better understand how associative memory is stored in single Kenyon cells a thorough description of single Kenyon cell morphology is crucial. Thus, a set of single Kenyon cells of the γ-type were stained individually using Mosaic Analysis with a Repressible Cell Marker (MARCM). Quantitative comparison of γ Kenyon cell morphologies revealed a broad variability of cell shapes, while differences between individual cell morphologies were continuous. However, subdivision of cell types according to bifurcation was possible. If this subdivision is related to Kenyon cell functionality has to be proven by further experiments. Furthermore, analysis of Kenyon cell innervations within functionally specialized compartments of the γ lobe revealed no compartment-specific Kenyon cell subtypes. In a second step structural plasticity of Kenyon cells was assessed using the same type of morphological analysis for all three major Kenyon cell classes of the γ-, α’/β’-, and α/β-type by exposing flies to different feeding conditions that were proven to affect Kenyon cell connectivity to extrinsic neurons involved in memory formation. However, in none of the cell types major morphological changes were observed. It seems likely that in the case of food intake mushroom body extrinsic neurons undergo adaptive changes, while Kenyon cells do not change morphologically.
Keywords: Learning; Memory; Mushroom body; Kenyon cell; Plasticity
