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Martin Heisenberg

Publications and source records attributed to Martin Heisenberg.

6 recordsLinked to original sources
PubMed2002

Extinction antagonizes olfactory memory at the subcellular level.

Memory loss occurs by diverse mechanisms, as different time constants of performance decrement and sensitivities to experimental manipulations suggest. While the phenomena of memory decay, interference, and extinction are well established behaviorally, little is known about them at the circuit or molecular level. In Drosophila, odorant memories lasting up to 3 hr can be localized to mushroom body Kenyon cells, a single neuronal level in the olfactory pathway. The plasticity underlying this memory trace can be induced without Kenyon cell synaptic output. Experimental extinction, i.e., presentation of the conditioned stimulus without the reinforcer, reduces memory performance and does so at the same circuit level as memory formation. Thus, unreinforced presentation of learned odorants antagonizes intracellularly the signaling cascade underlying memory formation.

Animals↗
PubMed2002

Targeted expression of tetanus neurotoxin interferes with behavioral responses to sensory input in Drosophila.

Targeted inactivation of neurons by expression of toxic gene products is a useful tool to assign behavioral functions to specific neurons or brain structures. Of a variety of toxic gene products tested, tetanus neurotoxin light chain (TNT) has the least severe side effects and can completely block chemical synapses. By using the GAL4 system to drive TNT expression in a subset of chemo- and mechanosensory neurons, we detected walking and flight defects consistent with blocking of relevant sensory information. We also found, for the first time, an olfactory behavioral phenotype associated with blocking of a specific subset of antennal chemoreceptors. Similar behavioral experiments with GAL4 lines expressing in different subsets of antennal chemoreceptors should contribute to an understanding of olfactory coding in Drosophila. To increase the utility of the GAL4 system for such purposes, we have designed an inducible system that allows us to circumvent lethality caused by TNT expression during early development.

Alleles↗
PubMed2002

The Drosophila standard brain.

Organisms and organs come in sizes and shapes. With size, science has no problems, but how to quantify shape? How similar are two birds or two brains? This problem is particularly pressing in cases like brains where structure reflects function. The problem is not new, but satisfying solutions have yet to be worked out. For brain anatomy, no general methodology for a statistically secured quantitative description is available. Using the small brain of the fly Drosophila melanogaster, we have explored a new approach combining immunohistochemistry, high-resolution 3D confocal microscopy, and advanced graphics computing. For a genetic model organism such as Drosophila, a quantitative assessment of brain structure is particularly rewarding, since it allows for the identification of genetic variants with subtle brain structure phenotypes and, even more importantly, the organization of the wealth of gene expression patterns in the brain into a genetic atlas linking molecular and organismic gene function. We now provide a representative standard for the brain of D. melanogaster wild-type with means and variances for several aspects of its shape. Its application to volumetry, mutants, and gene expression patterns is demonstrated.

Animals↗
PubMedDate not supplied

Memories in drosophila heat-box learning.

Learning and memory processes of operant conditioning in the heat-box are analyzed. In a search for conditioning parameters leading to high retention scores, intermittent training is shown to give better results than those of continuous training. Immediate retention tests contain two memory components, a spatial preference for one side of the chamber and a "stay-where-you-are-effect." Intermittent training strengthens the latter. In the second part, memory dynamics is investigated. Flies are trained in one chamber and tested in a second one after a brief reminder training. With this direct transfer, memory scores reflect an associative learning process in the first chamber. To investigate memory retention after extended time periods, indirect transfer experiments are performed. The fly is transferred to a different environment between training and test phases. With this procedure, an aftereffect of the training can still be observed 2 h later. Surprisingly, exposure to the chamber without conditioning also leads to a memory effect in the indirect transfer experiment. This exposure effect reveals a dispositional change that facilitates operant learning during the reminder training. The various memory effects are independent of the mushroom bodies.

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