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Different transgenes that can be expressed in neurons to kill or block them were compared. Tetanus neurotoxin blocked chemical synapses very efficiently. Synapses consisting of a chemical and an electrical component were blocked more reliably by expressing a human inwardly rectifying potassium channel. To gain temporal control over neuronal function, three genetic tools have been investigated. None of the systems is without drawbacks, however, the recombination induced tetanus neurotoxin expression is a promising approach. The knowledge gained from the comparative methodological study was used to investigate the role of neurons in sensory systems in processing different sensory informations. Receptor neurons sensitive for chemical or mechanical stimuli were correlated to specific olfactory behaviors or locomotor tasks. The main topic of this thesis is the much discussed question of which neurons are involved in motion processing in the visual system of flies. Neither L2 nor L4 neurons in the first visual neuropil are essential for motion-detection. The results indicate that maybe motion is detected by the network of amacrine cells (a). The vertical motion-sensitive VS cells in the lobula plate are not necessary for behavioral responses to vertical motion. This finding implies that the lack of VS cells in the structural mutant optomotor blind is not causally related to the altered responses to motion stimuli. Other abnormalities in optomotor blind are responsible for this behavioral phenotype. This work shows the potential of the described methods in studying information processing in the Drosophila brain. Groups of neurons were correlated to complex behavioral responses and theories about information processing were tested by behavioral experiments with transgenic flies. The refinement of the genetic tools to interfere with neuronal function will make the Drosophila brain an even better model to study information processing in nervous systems.
Previous research has shown that low-level visual features (i.e., low-level visual saliency) as well as socially relevant information predict gaze allocation in free viewing conditions. However, these studies mainly used static and highly controlled stimulus material, thus revealing little about the robustness of attentional processes across diverging situations. Secondly, the influence of affective stimulus characteristics on visual exploration patterns remains poorly understood. Participants in the present study freely viewed a set of naturalistic, contextually rich video clips from a variety of settings that were capable of eliciting different moods. Using recordings of eye movements, we quantified to what degree social information, emotional valence and low-level visual features influenced gaze allocation using generalized linear mixed models. We found substantial and similarly large regression weights for low-level saliency and social information, affirming the importance of both predictor classes under ecologically more valid dynamic stimulation conditions. Differences in predictor strength between individuals were large and highly stable across videos. Additionally, low-level saliency was less important for fixation selection in videos containing persons than in videos not containing persons, and less important for videos perceived as negative. We discuss the generalizability of these findings and the feasibility of applying this research paradigm to patient groups.