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The present study was conducted to provide evidence of conditioned taste aversion learning (CTA) in the snail Cornu aspersum, using quinidine as the aversive stimulus in a procedure of Pavlovian Conditioning of Tentacle Lowering. Subjects were split into two groups: paired and unpaired. During the devaluation phase, subjects from the “paired group” received the US followed by the quinidine exposure, while subjects from the “unpaired group” received the quinidine and, 30 min later, the US. Subjects which had received the US paired with the quinidine showed a decrease of the conditioned response (CR), in contrast to subjects which had received the quinidine and the US unpaired. These results provide a useful CTA procedure in terrestrial snails. The implication of the results for learning and the physiological correlates is discussed.

Taste aversion learning is universal. In animals, a single presentation of a novel food substance followed hours later by visceral illness causes animals to avoid that taste. This is known as bait-shyness or the Garcia effect. Humans demonstrate this by avoiding a certain food following the development of nausea after ingesting that food (‘Sauce Bearnaise effect’). Here, we show that the pond snail Lymnaea stagnalis is capable of the Garcia effect. A single ‘pairing’ of a novel taste, a carrot slurry followed hours later by a heat shock stressor (HS) is sufficient to suppress feeding response elicited by carrot for at least 24 h. Other food tastes are not suppressed. If snails had previously been exposed to carrot as their food source, the Garcia-like effect does not occur when carrot is ‘paired’ with the HS. The HS up-regulates two heat shock proteins (HSPs), HSP70 and HSP40. Blocking the up-regulation of the HSPs by a flavonoid, quercetin, before the heat shock, prevented the Garcia effect in the snails. Finally, we found that snails exhibit Garcia effect following a period of food deprivation but the long-term memory (LTM) phenotype can be observed only if the animals are tested in a food satiated state.

Four experiments with rat subjects asked whether a partial reinforcement extinction effect (PREE) occurs in taste aversion learning. The question has received little attention in the literature, and to our knowledge no taste aversion experiment has previously demonstrated a PREE. In each of the present experiments, experimental groups received a taste mixed in drinking water for 20 min; such taste exposures were sometimes paired with a lithium chloride (LiCl) injection and sometimes not. Control groups received only taste-LiCl pairings. There was evidence that each reinforced and non-reinforced trial produced increments and decrements in aversion strength (respectively), and trials mattered more than accumulated time during the conditioned stimulus and during the background (as emphasized in time-accumulation models like those of Gallistel and Gibbon, Psychological Review, 107, 289-344, 2000, and Gibbon and Balsam, Autoshaping and conditioning theory, Academic Press, New York, pp. 219-235, 1981). In addition, a partial reinforcement extinction effect was observed when there was a relatively large number of conditioning trials. The results extend our understanding of extinction in taste aversion learning and provide more evidence that aversion learning might follow rules that are qualitatively similar to those of other forms of learning.

While studies of the gustatory cortex (GC) mostly focus on its role in taste aversion learning and memory, the necessity of GC for other fundamental taste-guided behaviors remains largely untested. Here, rats with either excitotoxic lesions targeting GC (n = 26) or sham lesions (n = 14) were assessed for postsurgical retention of a presurgically LiCl-induced conditioned taste aversion (CTA) to 0.1M sucrose using a brief-access taste generalization test in a gustometer. The same animals were then trained in a two-response operant taste detection task and psychophysically tested for their salt (NaCl or KCl) sensitivity. Next, the rats were trained and tested in a NaCl vs. KCl taste discrimination task with concentrations varied. Rats meeting our histological inclusion criterion had large lesions (resulting in a group averaging 80% damage to GC and involving surrounding regions) and showed impaired postsurgical expression of the presurgical CTA (LiCl-injected, n = 9), demonstrated rightward shifts in the NaCl (0.54 log10 shift) and KCl (0.35 log10 shift) psychometric functions, and displayed retarded salt discrimination acquisition (n = 18), but eventually learned and performed the discrimination comparable to sham-operated animals. Interestingly, the degree of deficit between tasks correlated only modestly, if at all, suggesting that idiosyncratic differences in insular cortex lesion topography were the root of the individual differences in the behavioral effects demonstrated here. This latter finding hints at some degree of interanimal variation in the functional topography of insular cortex. Overall, GC appears to be necessary to maintain normal taste sensitivity to NaCl and KCl and for salt discrimination learning. However, higher salt concentrations can be detected and discriminated by rats with extensive damage to GC suggesting that the other resources of the gustatory system are sufficient to maintain partial competence in these tasks, supporting the view that such basic sensory-discriminative taste functions involve distributed processes among central gustatory structures.

This set of experiments examined the question of when a stimulus would be most effective in overshadowing the acquisition of long-delay taste aversion learning. In Experiment 1 rats drank sucrose, the target solution, followed by a hydrochloric acid (HCl) solution before lithium injection some time later; HCl was presented either early or late in the interval. The late condition produced greater overshadowing than the early condition. The importance of the HCl-injection interval was confirmed by Experiment 2 , in which the sucrose-injection interval was varied. Experiment 3 found that even placement in a different context – an event that normally produces little overshadowing of a CTA – produced one-trial overshadowing of a sucrose aversion as long as the context was novel and exposure to it occurred immediately before lithium injection. No current theoretical account of one-trial overshadowing predicts that a late event produces more overshadowing than an early event. This result can, however, be accommodated within a modified version of the Rescorla-Wagner model.

Artificial neural networks are computational network models inspired by signal processing in the brain. These models have dramatically improved performance for many machine-learning tasks, including speech and image recognition. However, today's computing hardware is inefficient at implementing neural networks, in large part because much of it was designed for von Neumann computing schemes. Significant effort has been made towards developing electronic architectures tuned to implement artificial neural networks that exhibit improved computational speed and accuracy. Here, we propose a new architecture for a fully optical neural network that, in principle, could offer an enhancement in computational speed and power efficiency over state-of-the-art electronics for conventional inference tasks. We experimentally demonstrate the essential part of the concept using a programmable nanophotonic processor featuring a cascaded array of 56 programmable Mach–Zehnder interferometers in a silicon photonic integrated circuit and show its utility for vowel recognition. Programmable silicon nanophotonic processor empowers optical neural networks.

Big data, we have all heard, promise to transform health care. But in the “hype cycle” of emerging technologies, machine learning now rides atop the “peak of inflated expectations,” and we need to better appreciate the technology’s capabilities and limitations. Big data, we have all heard, promise to transform health care with the widespread capture of electronic health records and high-volume data streams from sources ranging from insurance claims and registries to personal genomics and biosensors. 1 Artificial-intelligence and machine-learning predictive algorithms, which can already automatically drive cars, recognize spoken language, and detect credit card fraud, are the keys to unlocking the data that can precisely inform real-time decisions. But in the “hype cycle” of emerging technologies, machine learning now rides atop the “peak of inflated expectations.” 2 Prediction is not new to medicine. From risk scores to guide anticoagulation (CHADS2) and . . .

It is well known that pairing of large contextual changes with illness can cause conditioned context aversion in laboratory rats. The aim of present study was to develop a paradigm to study this phenomenon in laboratory mice, a species widely employed in neurobehavioral studies. Genetically heterogeneous mice, drinking from plastic bottles in the colony room, learned to avoid glass bottles after a single conditioning trial when drinking from these was paired with injections of lithium chloride. The aversion was independent of any difference in the taste of water in plastic vs. glass bottles. When the variation in the visual stimulus was less distinct, development of a strong aversion required two conditioning trials and was not retained as well. The results also showed that conditioned context aversion, just like conditioned taste aversion, could also be developed across a 30–minute CS–UCS delay. The fact that taste was not a factor in distinguishing drinking from glass and plastic water bottles raises the possibility that, contextual stimuli, not taste, may have been the CS when rats (in Garcia’s original experiments) avoided drinking from plastic bottles that had been paired with radiation. The development of contextual aversion conditioning protocols for mice will enable the molecular resources available for this species to be exploited. Furthermore, representation of the CS by discrete rather than the multimodal CSs typically used in most studies on contextual conditioning offers more focus when considering its neuroanatomical basis.