1,721,008 research outputs found
Age-related decrease in appetitive associative memory in fruit flies
No full textMemory scores are dynamic across developmental stages. In particular, memory scores typically decrease from late adolescence into old age, reflecting complex changes in mnemonic and sensory-motor faculties, metabolic and motivational changes, and changes in cognitive strategy as well. In Drosophila melanogaster, such age-related decreases in memory scores have been studied intensely for the association of odours with electric shock punishment. We report that odour-sucrose reward memory scores likewise decrease as the flies age. This was observed after one-trial and after two-trial conditioning, and for both immediate testing and recall tests 1 day later. This decrease was particularly pronounced in relatively young animals, in the first 2-3 weeks after adult hatching, and was more pronounced in female than in male flies
One-trial learning in larval Drosophila
No full textAnimals of many species are capable of "small data" learning, that is, of learning without repetition. Here we introduce larval Drosophila melanogaster as a relatively simple study case for such one-trial learning. Using odor-food associative conditioning, we first show that a sugar that is both sweet and nutritious (fructose) and sugars that are only sweet (arabinose) or only nutritious (sorbitol) all support appetitive one-trial learning. The same is the case for the optogenetic activation of a subset of dopaminergic neurons innervating the mushroom body, the memory center of the insects. In contrast, no one-trial learning is observed for an amino acid reward (aspartic acid). As regards the aversive domain, one-trial learning is demonstrated for high-concentration sodium chloride, but is not observed for a bitter tastant (quinine). Second, we provide follow-up, parametric analyses of odor-fructose learning. Specifically, we ascertain its dependency on the number and duration of training trials, the requirements for the behavioral expression of one-trial odor-fructose memory, its temporal stability, and the feasibility of one-trial differential conditioning. Our results set the stage for a neurogenetic analysis of one-trial learning and define the requirements for modeling mnemonic processes in the larva
An optogenetic analogue of second-order reinforcement in Drosophila
No full textIn insects, odours are coded by the combinatorial activation of ascending pathways, including their third-order representation in mushroom body Kenyon cells. Kenyon cells also receive intersecting input from ascending and mostly dopaminergic reinforcement pathways. Indeed, in Drosophila, presenting an odour together with activation of the dopaminergic mushroom body input neuron PPL1-01 leads to a weakening of the synapse between Kenyon cells and the approach-promoting mushroom body output neuron MBON-11. As a result of such weakened approach tendencies, flies avoid the shock-predicting odour in a subsequent choice test. Thus, increased activity in PPL1-01 stands for punishment, whereas reduced activity in MBON-11 stands for predicted punishment. Given that punishment-predictors can themselves serve as punishments of second order, we tested whether presenting an odour together with the optogenetic silencing of MBON-11 would lead to learned odour avoidance, and found this to be the case. In turn, the optogenetic activation of MBON-11 together with odour presentation led to learned odour approach. Thus, manipulating activity in MBON-11 can be an analogue of predicted, second-order reinforcement
Pharmacological dissociation between the reinforcing, sensitizing, and response-releasing functions of reward in honeybee classical conditioning
No full textReserpine depletes biogenic amines from their stores in the honeybee (Apis mellifera camica) brain and leads to impaired appetitive conditioning using sucrose as a reinforcer. Compensatory injection of octopamine or dopamine directly into the brain restores these behavioral losses. Dopamine rescues the slowing-down effect on motor patterns, but not sensitization or conditioning. Octopamine leaves the motor patterns as well as sensitization unchanged but rescues conditioning. Specifically, octopamine rescues acquisition but not retrieval. Serotonin has no significant effect on sensitization but impairs conditioning. The authors conclude that octopamine is involved in selectively mediating the reinforcing but not the sensitizing or response-releasing function of the sucrose reward, whereas dopamine is selectively involved in the expression of the motor response. (APA PsycInfo Database Record (c) 2016 APA, all rights reserved
Optogenetically induced reward and ‘frustration’ memory in larval <i>Drosophila melanogaster</i>
No full textABSTRACT
Animals, including humans, form oppositely valenced memories for stimuli that predict the occurrence versus the termination of a reward: appetitive ‘reward’ memory for stimuli associated with the occurrence of a reward and aversive ‘frustration’ memory for stimuli that are associated with its termination. We characterized these memories in larval Drosophila melanogaster using a combination of Pavlovian conditioning, optogenetic activation of the dopaminergic central-brain DAN-i1864 neuron, and high-resolution video-tracking. This reveals their dependency on the number of training trials and the duration of DAN-i1864 activation, their temporal stability, and the parameters of locomotion that are modulated during memory expression. Together with previous results on ‘punishment’ versus ‘relief’ learning by DAN-f1 neuron activation, this reveals a 2×2 matrix of timing-dependent memory valence for the occurrence/termination of reward/punishment. These findings should aid the understanding and modelling of how brains decipher the predictive, causal structure of events around a target reinforcing occurrence.</jats:p
A quick and versatile protocol for the 3D visualization of transgene expression across the whole body of larval Drosophila
No full textLarval Drosophila are used as a genetically accessible study case in many areas of biological research. Here we report a fast, robust and user-friendly procedure for the whole-body multi-fluorescence imaging of Drosophila larvae; the protocol has been optimized specifically for larvae by systematically tackling the pitfalls associated with clearing this small but cuticularized organism. Tests on various fluorescent proteins reveal that the recently introduced monomeric infrared fluorescent protein (mIFP) is particularly suitable for our approach. This approach comprises an effective, low-cost clearing protocol with minimal handling time and reduced toxicity in the reagents employed. It combines a success rate high enough to allow for small-scale screening approaches and a resolution sufficient for cellular-level analyses with light sheet and confocal microscopy. Given that publications and database documentations typically specify expression patterns of transgenic driver lines only within a given organ system of interest, the present procedure should be versatile enough to extend such documentation systematically to the whole body. As examples, the expression patterns of transgenic driver lines covering the majority of neurons, or subsets of chemosensory, central brain or motor neurons, are documented in the context of whole larval body volumes (using nsyb-Gal4, IR76b-Gal4, APL-Gal4 and mushroom body Kenyon cells, or OK371-Gal4, respectively). Notably, the presented protocol allows for triple-color fluorescence imaging with near-infrared, red and yellow fluorescent proteins
Timing-dependent valence reversal: a principle of reinforcement processing and its possible implications
No full textPunishment feels bad, but relief upon its termination feels good. As a consequence of such timing-dependent valence reversal, memories of opposite valence can result from associating stimulus A with, for example, the occurrence of punishment (A−) versus punishment termination (−A): A− training results in aversive memory, but −A training in appetitive memory (corresponding effects exist for reward occurrence and termination). Whereas learning through the occurrence of punishment is well studied, much less is known about learning through its termination. Current research investigates how dopaminergic system function contributes to these processes in Drosophila, rats and humans. We argue that dopamine-related psychopathology may entail distortions in learning through punishment termination, and that this may contribute, for example, to non-suicidal self-injury or post-traumatic stress disorder
A quick and versatile protocol for the 3D visualization of transgene expression across the whole body of larval Drosophila
No full textPrediction error drives associative olfactory learning and conditioned behavior in a spiking model of Drosophila larva
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