CiteULike: brembs's behavior

Regulation of firing of dopaminergic neurons and control of goal-directed behaviors

Anthony Grace — 2007-04-04T14:05:09-00:00

Trends in Neurosciences, Vol. In Press, Corrected Proof

There are several brain regions that have been implicated in the control of motivated behavior and whose disruption leads to the pathophysiology observed in major psychiatric disorders. These systems include the ventral hippocampus, which is involved in context and focus on tasks, the amygdala, which mediates emotional behavior, and the prefrontal cortex, which modulates activity throughout the limbic system to enable behavioral flexibility. Each of these systems has overlapping projections to the nucleus accumbens, where these inputs are integrated under the modulatory influence of dopamine. Here, we provide a systems-oriented approach to interpreting the function of the dopamine system, its modulation of limbic-cortical interactions and how disruptions within this system might underlie the pathophysiology of schizophrenia and drug abuse.

Order in spontaneous behavior

Alexander Maye — 2005-01-20T00:29:54-00:00

PLoS One, Vol. 2, No. 5. (May 2007), e443.

Context and occasion setting in Drosophila visual learning.

B Brembs — 2006-11-17T14:42:36-00:00

Learn Mem, Vol. 13, No. 5. (t 2006), pp. 618-628.

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.

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

B Brembs — 2006-11-17T14:41:38-00:00

Learn Mem, Vol. 13, No. 5. (t 2006), pp. 629-637.

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.

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

A Baier — 2006-09-29T06:48:43-00:00

J Exp Biol, Vol. 205, No. Pt 9. (May 2002), pp. 1233-1240.

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.

Conditioning with compound stimuli in Drosophila melanogaster in the flight simulator.

B Brembs — 2006-09-29T06:48:43-00:00

J Exp Biol, Vol. 204, No. Pt 16. (August 2001), pp. 2849-2859.

Short-term memory in Drosophila melanogaster operant visual learning in the flight simulator is explored using patterns and colours as a compound stimulus. Presented together during training, the two stimuli accrue the same associative strength whether or not a prior training phase rendered one of the two stimuli a stronger predictor for the reinforcer than the other (no blocking). This result adds Drosophila to the list of other invertebrates that do not exhibit the robust vertebrate blocking phenomenon. Other forms of higher-order learning, however, were detected: a solid sensory preconditioning and a small second-order conditioning effect imply that associations between the two stimuli can be formed, even if the compound is not reinforced.

Flexibility in a single behavioral variable of Drosophila.

M Heisenberg — 2006-09-29T06:48:45-00:00

Learn Mem, Vol. 8, No. 1. (b 2001), pp. 1-10.

The flexibility of behavior is so rich, and its components are so exquisitely interwoven, that one may be well advised to turn to an isolated behavioral module for study. Gill withdrawal in Aplysia, the proboscis extension reflex in the honeybee, and lid closure in mammals are such examples. We have chosen yawing, a single component of flight orientation in Drosophila melanogaster, for this approach. A specialty of this preparation is that the behavioral output can be reduced beyond the single module by one further step. It can be studied in tethered animals in which all turns are blocked while the differentially beating wings still provide the momentum. These intended yaw turns are measured by a torque meter to which the fly is hooked. The fly is held horizontally as if cruising at high speed. The head is glued to the thorax. It can bend its abdomen, extend its proboscis, and move its legs but cannot shift its direction of gaze or its orientation in space. Evidently, a fly hardly ever encounters this bizarre situation in the wild. We describe here the flexibility in this single behavioral variable. It provides insights into the relation between classical and operant conditioning, the processing of and interactions between the conditioned visual stimuli, early visual memory, visual pattern recognition, selective attention, and several other experience-dependent properties of visual orientation behavior. We start with a brief summary of visual flight control at the torque meter.

The operant and the classical in conditioned orientation of Drosophila melanogaster at the flight simulator.

B Brembs — 2006-09-29T06:48:45-00:00

Learn Mem, Vol. 7, No. 2. (r 2000), pp. 104-115.

Ever since learning and memory have been studied experimentally, the relationship between operant and classical conditioning has been controversial. Operant conditioning is any form of conditioning that essentially depends on the animal's behavior. It relies on operant behavior. A motor output is called operant if it controls a sensory variable. The Drosophila flight simulator, in which the relevant behavior is a single motor variable (yaw torque), fully separates the operant and classical components of a complex conditioning task. In this paradigm a tethered fly learns, operantly or classically, to prefer and avoid certain flight orientations in relation to the surrounding panorama. Yaw torque is recorded and, in the operant mode, controls the panorama. Using a yoked control, we show that classical pattern learning necessitates more extensive training than operant pattern learning. We compare in detail the microstructure of yaw torque after classical and operant training but find no evidence for acquired behavioral traits after operant conditioning that might explain this difference. We therefore conclude that the operant behavior has a facilitating effect on the classical training. In addition, we show that an operantly learned stimulus is successfully transferred from the behavior of the training to a different behavior. This result unequivocally demonstrates that during operant conditioning classical associations can be formed.

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

AM Phillips — 2006-09-29T06:47:26-00:00

Gene, Vol. 351 (23 May 2005), pp. 131-142.

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.