[Show abstract][Hide abstract] ABSTRACT: A visual stimulus at a particular location of the visual field may elicit a behavior while at the same time equally salient stimuli in other parts do not. This property of visual systems is known as selective visual attention (SVA). The animal is said to have a focus of attention (FoA) which it has shifted to a particular location. Visual attention normally involves an attention span at the location to which the FoA has been shifted. Here the attention span is measured in Drosophila. The fly is tethered and hence has its eyes fixed in space. It can shift its FoA internally. This shift is revealed using two simultaneous test stimuli with characteristic responses at their particular locations. In tethered flight a wild type fly keeps its FoA at a certain location for up to 4s. Flies with a mutation in the radish gene, that has been suggested to be involved in attention-like mechanisms, display a reduced attention span of only 1s.
[Show abstract][Hide abstract] ABSTRACT: Abstract Novelty choice, a visual paired-comparison task for the fly Drosophila melanogaster is studied with severely restrained single animals in a flight simulator. The virtual environment simulates free flight for rotation in the horizontal plane. The behavior has three functional components: visual azimuth orientation, working memory and pattern discrimination (perception). Here we study novelty choice in relation to its neural substrate in the brain and show that it requires the central complex and in particular the ring neurons of the ellipsoid body. Surprisingly, it also involves the mushroom bodies which are needed specifically in the comparison of patterns of different size.
Preview · Article · Jan 2015 · Journal of Neurogenetics
[Show abstract][Hide abstract] ABSTRACT: Abstract Behavior is not adequately described as a stimulus - response process. It is initiated by the animal and is generated because of its expected outcome in the future. The outcome can be good or bad for the animal. The brain is in charge of the selection process. This is the basic function of the brain. Taking Drosophila as a study case the essay discusses initiating activity, several examples of outcome expectations, trying out, the internal search for a suitable behavior, chaining of actions and the functional roles of chance in action selection. It takes mental processes and states such as goals, intentions, feelings, memories, cognition and attention as higher levels of behavioral control that have their origin in biological evolution.
No preview · Article · Apr 2014 · Journal of neurogenetics
[Show abstract][Hide abstract] ABSTRACT: Despite the importance of the insect nervous system for functional and developmental neuroscience, descriptions of insect brains have suffered from a lack of uniform nomenclature. Ambiguous definitions of brain regions and fiber bundles have contributed to the variation of names used to describe the same structure. The lack of clearly determined neuropil boundaries has made it difficult to document precise locations of neuronal projections for connectomics study. To address such issues, a consortium of neurobiologists studying arthropod brains, the Insect Brain Name Working Group, has established the present hierarchical nomenclature system, using the brain of Drosophila melanogaster as the reference framework, while taking the brains of other taxa into careful consideration for maximum consistency and expandability. The following summarizes the consortium's nomenclature system and highlights examples of existing ambiguities and remedies for them. This nomenclature is intended to serve as a standard of reference for the study of the brain of Drosophila and other insects.
[Show abstract][Hide abstract] ABSTRACT: In a wide range of animals, uncontrollable stressful events can induce a condition called "learned helplessness." In mammals it is associated with low general activity, poor learning, disorders of sleep and feeding, ulcers, and reduced immune status, as well as with increased serotonin in parts of the brain. It is considered an animal model of depression in humans [1-4]. Here we investigate learned helplessness in Drosophila, showing that this behavioral state consists of a cognitive and a modulatory, possibly mood-like, component. A fly, getting heated as soon as it stops walking, reliably resumes walking to escape the heat. If, in contrast, the fly is not in control of the heat, it learns that its behavior has no effect and quits responding. In this state, the fly walks slowly and takes longer and more frequent rests, as if it were "depressed." This downregulation of walking behavior is more pronounced in females than in males. Learned helplessness in Drosophila is an example of how, in a certain situation, behavior is organized according to its expected consequences.
Preview · Article · Apr 2013 · Current biology: CB
[Show abstract][Hide abstract] ABSTRACT: Behaviour of humans and most animals can be free. Behaviour is free if the subject does of her/his own accord what must be done. Action selection is the main task of a brain. The search for the right behaviour is demanding because it requires assessing the possible consequences of the available behavioural options. Freedom is reduced externally, if fewer adaptive behavioural options are available or internally, if the search process in the brain is impaired. Most animal societies enforce cooperation at the expense of individual freedom. In contrast, human societies can base cooperation on shared intentions. In this way the individuals can cooperate without sacrificing behavioural freedom.
[Show abstract][Hide abstract] ABSTRACT: This essay is dedicated to Obaid on the occasion of his 80th birthday. We both worked on the behavior of Drosophila and on what underlies behavior in the fly brain. Is that the fly's mind? The essay is about some limitations of brain science. It is just a little piece of writing. It is meant to honor Obaid for his contributions to Drosophila neurogenetics in 40 years and to science in India. I hope he takes it instead of a bowl of flowers-adding to the praise.
No preview · Article · May 2012 · Journal of neurogenetics
[Show abstract][Hide abstract] ABSTRACT: Visual behavior of insects has long been studied, but it is only recently that a wide variety of genetic tools has become available for its analysis. Perhaps the most basic visual behaviour is phototaxis, locomotion towards a source of light. It is known in many insects and has been studied for over a century but the neural network underlying it is little understood. We recently described in the fruit fly Drosophila how different photoreceptor types contribute to phototaxis. By blocking subsets of them we showed that at least four of the five types are involved. In this short review, we compare phototactic behaviour in fruit flies and other insects (especially honeybees), and discuss what is known about the underlying neural circuitry. :
[Show abstract][Hide abstract] ABSTRACT: Organisms with complex visual systems rarely respond to just the sum of all visual stimuli impinging on their eyes. Often, they restrict their responses to stimuli in a temporarily selected region of the visual field (selective visual attention). Here, we investigate visual attention in the fly Drosophila during tethered flight at a torque meter. Flies can actively shift their attention; however, their attention can be guided to a certain location by external cues. Using visual cues, we can direct the attention of the fly to one or the other of the two visual half-fields. The cue can precede the test stimulus by several seconds and may also be spatially separated from the test by at least 20° and yet attract attention. This kind of external guidance of attention is found only in the lower visual field.
Preview · Article · Apr 2011 · Proceedings of the National Academy of Sciences
[Show abstract][Hide abstract] ABSTRACT: Software. The JAR archive, containing both binary classes and the Java source code of our software. To install the software, this file must be copied into ImageJ's plugins directory.
[Show abstract][Hide abstract] ABSTRACT: Current imaging methods such as Magnetic Resonance Imaging (MRI), Confocal microscopy, Electron Microscopy (EM) or Selective Plane Illumination Microscopy (SPIM) yield three-dimensional (3D) data sets in need of appropriate computational methods for their analysis. The reconstruction, segmentation and registration are best approached from the 3D representation of the data set.
Here we present a platform-independent framework based on Java and Java 3D for accelerated rendering of biological images. Our framework is seamlessly integrated into ImageJ, a free image processing package with a vast collection of community-developed biological image analysis tools. Our framework enriches the ImageJ software libraries with methods that greatly reduce the complexity of developing image analysis tools in an interactive 3D visualization environment. In particular, we provide high-level access to volume rendering, volume editing, surface extraction, and image annotation. The ability to rely on a library that removes the low-level details enables concentrating software development efforts on the algorithm implementation parts.
Our framework enables biomedical image software development to be built with 3D visualization capabilities with very little effort. We offer the source code and convenient binary packages along with extensive documentation at http://3dviewer.neurofly.de.
[Show abstract][Hide abstract] ABSTRACT: Supplementary material. Top, demonstration of landmark selection in two different adult Drosophila brains, for the purpose of landmark-based image volume registration. Bottom, source code example implementing the dendritic growth simulation shown in Figure 4 of the main manuscript.
[Show abstract][Hide abstract] ABSTRACT: Direct volume editing. A movie which shows the result of the simulated dendritic growth. The corresponding source code is presented in Additional file 1, section 2.
[Show abstract][Hide abstract] ABSTRACT: The visual systems of most species contain photoreceptors with distinct spectral sensitivities that allow animals to distinguish lights by their spectral composition. In Drosophila, photoreceptors R1-R6 have the same spectral sensitivity throughout the eye and are responsible for motion detection. In contrast, photoreceptors R7 and R8 exhibit heterogeneity and are important for color vision. We investigated how photoreceptor types contribute to the attractiveness of light by blocking the function of certain subsets and by measuring differential phototaxis between spectrally different lights. In a "UV vs. blue" choice, flies with only R1-R6, as well as flies with only R7/R8 photoreceptors, preferred blue, suggesting a nonadditive interaction between the two major subsystems. Flies defective for UV-sensitive R7 function preferred blue, whereas flies defective for either type of R8 (blue- or green-sensitive) preferred UV. In a "blue vs. green" choice, flies defective for R8 (blue) preferred green, whereas those defective for R8 (green) preferred blue. Involvement of all photoreceptors [R1-R6, R7, R8 (blue), R8 (green)] distinguishes phototaxis from motion detection that is mediated exclusively by R1-R6.
Full-text · Article · Mar 2010 · Proceedings of the National Academy of Sciences
[Show abstract][Hide abstract] ABSTRACT: Most insertional mutagenesis screens of Drosophila performed to date have not used target chromosomes that have been checked for their suitability for phenotypic screens for viable phenotypes. To address this, we have generated a selection of stocks carrying either isogenized second chromosomes or isogenized third chromosomes, in a genetic background derived from a Canton-S wild-type strain. We have tested these stocks for a range of behavioral and other viable phenotypes. As expected, most lines are statistically indistinguishable from Canton-S in most phenotypes tested. The lines generated are now being used as target chromosomes in mutagenesis screens, and the characterization reported here will facilitate their use in screens of these lines for behavioral and other viable phenotypes.
Full-text · Article · Jul 2009 · Journal of Neurogenetics
[Show abstract][Hide abstract] ABSTRACT: Two Drosophila mutants are described in which the connections between the input to and the output from the mushroom bodies is largely interrupted. In all forms of the flies (larva, imago, male, female) showing the structural defect, olfactory conditioning is impaired. Learning is completely abolished when electroshock is used as reinforcement and partially suppressed in reward learning with sucrose. No influence of the mushroom body defect on the perception of the conditioning stimuli or on spontaneous olfactory behavior is observed. The defect seems not to impair learning of color discrimination tasks or operant learning involving visual cues.
No preview · Article · Jul 2009 · Journal of Neurogenetics