Biomedical subjects

Björn Brembs

Publications and source records attributed to Björn Brembs.

7 recordsLinked to original sources

PubMed2005

The Drosophila black enigma: the molecular and behavioural characterization of the black1 mutant allele.

The cuticular melanization phenotype of black flies is rescued by beta-alanine, but beta-alanine production, by aspartate decarboxylation, was reported to be normal in assays of black mutants, and although black/Dgad2 is expressed in the lamina, the first optic ganglion, no electroretinogram (ERG) or other visual defect has been demonstrated in black flies. The purpose of this study was to investigate the black gene, and protein, in black(1) mutants of Drosophila melanogaster in order to resolve the apparent paradox of the black phenotype. Using black(1) mutant flies we show that (1) aspartate decarboxylase activity is significantly reduced in adults and at puparium formation, consistent with defects in cuticular and non-cuticular processes, (2) that the black(1) mutation is a frameshift, and black(1) flies are nulls for the black/DGAD2 protein, and (3) that behavioural experiments using Buridan's paradigm, demonstrate that black responds abnormally to visual cues. No ERG, or target recognition defects can be demonstrated suggesting a problem with higher order visual functions in black mutants.

Alleles↗

PubMed2004

Extending in vitro conditioning in Aplysia to analyze operant and classical processes in the same preparation.

Operant and classical conditioning are major processes shaping behavioral responses in all animals. Although the understanding of the mechanisms of classical conditioning has expanded significantly, the understanding of the mechanisms of operant conditioning is more limited. Recent developments in Aplysia are helping to narrow the gap in the level of understanding between operant and classical conditioning, and have raised the possibility of studying the neuronal processes underlying the interaction of operant and classical components in a relatively complex learning task. In the present study, we describe a first step toward realizing this goal, by developing a single in vitro preparation in which both operant and classical conditioning can be studied concurrently. The new paradigm reproduced previously published results, even under more conservative and homogenous selection criteria and tonic stimulation regime. Moreover, the observed learning was resistant to delay, shortening, and signaling of reinforcement.

Analysis of Variance↗

PubMed2003

Operant conditioning in invertebrates.

Learning to anticipate future events on the basis of past experience with the consequences of one's own behavior (operant conditioning) is a simple form of learning that humans share with most other animals, including invertebrates. Three model organisms have recently made significant contributions towards a mechanistic model of operant conditioning, because of their special technical advantages. Research using the fruit fly Drosophila melanogaster implicated the ignorant gene in operant conditioning in the heat-box, research on the sea slug Aplysia californica contributed a cellular mechanism of behavior selection at a convergence point of operant behavior and reward, and research on the pond snail Lymnaea stagnalis elucidated the role of a behavior-initiating neuron in operant conditioning. These insights demonstrate the usefulness of a variety of invertebrate model systems to complement and stimulate research in vertebrates.

Animals↗

PubMed2002

Operant reward learning in Aplysia: neuronal correlates and mechanisms.

Operant conditioning is a form of associative learning through which an animal learns about the consequences of its behavior. Here, we report an appetitive operant conditioning procedure in Aplysia that induces long-term memory. Biophysical changes that accompanied the memory were found in an identified neuron (cell B51) that is considered critical for the expression of behavior that was rewarded. Similar cellular changes in B51 were produced by contingent reinforcement of B51 with dopamine in a single-cell analog of the operant procedure. These findings allow for the detailed analysis of the cellular and molecular processes underlying operant conditioning.

Animals↗

PubMed2002

Drosophila as a new model organism for the neurobiology of aggression?

We report here the effects of several neurobiological determinants on aggressive behaviour in the fruitfly Drosophila melanogaster. This study combines behavioural, transgenic, genetic and pharmacological techniques that are well established in the fruitfly, in the novel context of the neurobiology of aggression. We find that octopamine, dopamine and a region in the Drosophila brain called the mushroom bodies, all profoundly influence the expression of aggressive behaviour. Serotonin had no effect. We conclude that Drosophila, with its advanced set of molecular tools and its behavioural richness, has the potential to develop into a new model organism for the study of the neurobiology of aggression.

Aggression↗

PubMedDate not supplied

Context and occasion setting in Drosophila visual learning.

In a permanently changing environment, it is by no means an easy task to distinguish potentially important events from negligible ones. Yet, to survive, every animal has to continuously face that challenge. How does the brain accomplish this feat? Building on previous work in Drosophila melanogaster visual learning, we have developed an experimental methodology in which combinations of visual stimuli (colors and patterns) can be arranged such that the same stimuli can either be directly predictive, indirectly predictive, or nonpredictive of punishment. Varying this relationship, we found that wild-type flies can establish different memory templates for the same contextual color cues. The colors can either leave no trace in the pattern memory template, leading to context-independent pattern memory (context generalization), or be learned as a higher-order cue indicating the nature of the pattern-heat contingency leading to context-dependent memory (occasion setting) or serve as a conditioned stimulus predicting the punishment directly (simple conditioning). In transgenic flies with compromised mushroom-body function, the sensitivity to these subtle variations is altered. Our methodology constitutes a new concept for designing learning experiments. Our findings suggest that the insect mushroom bodies stabilize visual memories against context changes and are not required for cognition-like higher-order learning.

Adaptation, Physiological↗

PubMedDate not supplied

Different parameters support generalization and discrimination learning in Drosophila at the flight simulator.

We have used a genetically tractable model system, the fruit fly Drosophila melanogaster to study the interdependence between sensory processing and associative processing on learning performance. We investigated the influence of variations in the physical and predictive properties of color stimuli in several different operant-conditioning procedures on the subsequent learning performance. These procedures included context and stimulus generalization as well as color, compound, and conditional discrimination (colors and patterns). A surprisingly complex dependence of the learning performance on the colors' physical and predictive properties emerged, which was clarified by taking into account the fly-subjective perception of the color stimuli. Based on estimates of the stimuli's color and brightness values, we propose that the different tasks are supported by different parameters of the color stimuli; generalization occurs only if the chromaticity is sufficiently similar, whereas discrimination learning relies on brightness differences.

Animals↗