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Neuroscience Sep 2011Learning and memory in the fruit fly, Drosophila melanogaster, is a complex behavior with many parallels to mammalian learning and memory. Although many...
Learning and memory in the fruit fly, Drosophila melanogaster, is a complex behavior with many parallels to mammalian learning and memory. Although many neurotransmitters including acetylcholine, dopamine, glutamate, and GABA have previously been demonstrated to be involved in aversive olfactory learning and memory, the role of serotonin has not been well defined. Here, we present the first evidence of the involvement of individual serotonin receptors in olfactory learning and memory in the fly. We initially followed a pharmacological approach, utilizing serotonin receptor agonists and antagonists to demonstrate that all serotonin receptor families present in the fly are necessary for short-term learning and memory. Isobolographic analysis utilizing combinations of drugs revealed functional interactions are occurring between 5-HT(1A)-like and 5-HT(2), and 5-HT(2) and 5-HT(7) receptor circuits in mediating short-term learning and memory. Examination of long-term memory suggests that 5-HT(1A)-like receptors are necessary for consolidation and important for recall, 5-HT(2) receptors are important for consolidation and recall, and 5-HT(7) receptors are involved in all three phases. Importantly, we have validated our pharmacological results with genetic experiments and showed that hypomorph strains for 5-HT(2)Dro and 5-HT(1B)Dro receptors, as well as knockdown of 5-HT(7)Dro mRNA, significantly impair performance in short-term memory. Our data highlight the importance of the serotonin system and individual serotonin receptors to influence olfactory learning and memory in the fly, and position the fly as a model system to study the role of serotonin in cognitive processes relevant to mammalian CNS function.
Topics: Animals; Brain; Conditioning, Classical; Drosophila melanogaster; Female; Learning; Male; Memory; Receptors, Serotonin; Smell
PubMed: 21749913
DOI: 10.1016/j.neuroscience.2011.06.058 -
Acta Psychologica Jan 2014This article reviews situations in which stimuli produce an increase or a decrease in nociceptive responses through basic associative processes and provides an... (Review)
Review
This article reviews situations in which stimuli produce an increase or a decrease in nociceptive responses through basic associative processes and provides an associative account of such changes. Specifically, the literature suggests that cues associated with stress can produce conditioned analgesia or conditioned hyperalgesia, depending on the properties of the conditioned stimulus (e.g., contextual cues and audiovisual cues vs. gustatory and olfactory cues, respectively) and the proprieties of the unconditioned stimulus (e.g., appetitive, aversive, or analgesic, respectively). When such cues are associated with reducers of exogenous pain (e.g., opiates), they typically increase sensitivity to pain. Overall, the evidence concerning conditioned stress-induced analgesia, conditioned hyperalagesia, conditioned tolerance to morphine, and conditioned reduction of morphine analgesia suggests that selective associations between stimuli underlie changes in pain sensitivity.
Topics: Analgesia; Analgesics, Opioid; Association Learning; Conditioning, Classical; Cues; Drug Tolerance; Humans; Hyperalgesia; Morphine; Smell; Stress, Psychological
PubMed: 24269884
DOI: 10.1016/j.actpsy.2013.10.009 -
ELife Jan 2019Practice makes perfect. In human olfaction, such plasticity is generally assumed to occur at the level of cortical synthetic processing that shares information from both...
Practice makes perfect. In human olfaction, such plasticity is generally assumed to occur at the level of cortical synthetic processing that shares information from both nostrils. Here we present findings that challenge this view. In two experiments, we trained human adults unirhinally for the discrimination between odor enantiomers over a course of about 10 to 11 days. Results showed that training-induced perceptual gain was restricted to the trained nostril yet partially generalized to untrained odor enantiomers in a structure- rather than quality- based manner. In other words, learning enhanced the differentiation of chirality (molecular configuration) as opposed to overall odor quality (odor object) per se. These findings argue that, unlike earlier beliefs, one nostril does not readily know what the other learns. Moreover, the initial analytical processing of the structural features of uninarial olfactory input remains plastic in human adults.
Topics: Adult; Butanols; Cyclohexane Monoterpenes; Discrimination Learning; Female; Humans; Limonene; Male; Nasal Cavity; Neuronal Plasticity; Odorants; Olfactory Pathways; Smell; Stereoisomerism; Young Adult
PubMed: 30652684
DOI: 10.7554/eLife.41296 -
Nature Neuroscience Oct 2008Sensory systems create neural representations of environmental stimuli and these representations can be associated with other stimuli through learning. Are spike...
Sensory systems create neural representations of environmental stimuli and these representations can be associated with other stimuli through learning. Are spike patterns the neural representations that get directly associated with reinforcement during conditioning? In the moth Manduca sexta, we found that odor presentations that support associative conditioning elicited only one or two spikes on the odor's onset (and sometimes offset) in each of a small fraction of Kenyon cells. Using associative conditioning procedures that effectively induced learning and varying the timing of reinforcement relative to spiking in Kenyon cells, we found that odor-elicited spiking in these cells ended well before the reinforcement was delivered. Furthermore, increasing the temporal overlap between spiking in Kenyon cells and reinforcement presentation actually reduced the efficacy of learning. Thus, spikes in Kenyon cells do not constitute the odor representation that coincides with reinforcement, and Hebbian spike timing-dependent plasticity in Kenyon cells alone cannot underlie this learning.
Topics: Action Potentials; Animals; Behavior, Animal; Conditioning, Classical; Manduca; Mushroom Bodies; Neuronal Plasticity; Neurons; Odorants; Olfactory Pathways; Reinforcement, Psychology; Sense Organs; Smell; Time Factors
PubMed: 18794840
DOI: 10.1038/nn.2192 -
Annals of the New York Academy of... Jul 2009Memory for olfactory stimuli may be particularly affected by age-related brain changes in humans and may be an early indicator of cognitive impairment and Alzheimer's...
Memory for olfactory stimuli may be particularly affected by age-related brain changes in humans and may be an early indicator of cognitive impairment and Alzheimer's disease. Studies involving rats have offered insights into impaired cognition in aged animals, but few have examined odor memory. Therefore, it is unclear whether aged rats are a good model for possible age-related changes in odor memory in humans. Young (6-month-old) and old (24-month-old) rats were tested on associative learning tasks involving visual and olfactory stimuli. The first task examined age-related differences in discrimination and reversal learning for olfactory and visual stimuli; the second task utilized an associative contextual learning task involving olfactory and visual cues. Although old rats were able to perform the olfactory and visual discrimination tasks as well as young rats, old rats displayed significant age-related impairment on the reversal learning and contextual learning tasks. The results suggest that aging may have a similar deleterious effect on odor memory in rats and in humans. The findings may have important implications for the selection of memory paradigms for future research studies on aging. In addition, the use of an animal model to investigate the effects of aging on odor memory will allow researchers the ability to investigate how age-related neuroanatomical and neurochemical changes may result in impaired odor memory.
Topics: Aging; Animals; Learning; Male; Odorants; Photic Stimulation; Rats; Rats, Inbred F344; Smell
PubMed: 19686218
DOI: 10.1111/j.1749-6632.2009.03929.x -
PloS One 2016In Southeast Asia the native honey bee species Apis cerana is often attacked by hornets (Vespa velutina), mainly in the period from April to November. During the...
In Southeast Asia the native honey bee species Apis cerana is often attacked by hornets (Vespa velutina), mainly in the period from April to November. During the co-evolution of these two species honey bees have developed several strategies to defend themselves such as learning the odors of hornets and releasing alarm components to inform other mates. However, so far little is known about whether and how honey bees modulate their olfactory learning in the presence of the hornet predator and alarm components of honey bee itself. In the present study, we test for associative olfactory learning of A. cerana in the presence of predator odors, the alarm pheromone component isopentyl acetate (IPA), or a floral odor (hexanal) as a control. The results show that bees can detect live hornet odors, that there is almost no association between the innately aversive hornet odor and the appetitive stimulus sucrose, and that IPA is less well associated with an appetitive stimulus when compared with a floral odor. In order to imitate natural conditions, e.g. when bees are foraging on flowers and a predator shows up, or alarm pheromone is released by a captured mate, we tested combinations of the hornet odor and floral odor, or IPA and floral odor. Both of these combinations led to reduced learning scores. This study aims to contribute to a better understanding of the prey-predator system between A. cerana and V. velutina.
Topics: Aldehydes; Animals; Appetitive Behavior; Arthropod Antennae; Avoidance Learning; Bees; Conditioning, Classical; Feeding Behavior; Female; Flowers; Learning; Memory; Odorants; Pentanols; Pheromones; Predatory Behavior; Reward; Smell; Species Specificity; Sucrose; Wasps
PubMed: 26919132
DOI: 10.1371/journal.pone.0150399 -
Current Opinion in Neurobiology Oct 2011Insects can learn, allowing them great flexibility for locating seasonal food sources and avoiding wily predators. Because insects are relatively simple and accessible... (Review)
Review
Insects can learn, allowing them great flexibility for locating seasonal food sources and avoiding wily predators. Because insects are relatively simple and accessible to manipulation, they provide good experimental preparations for exploring mechanisms underlying sensory coding and memory. Here we review how the intertwining of memory with computation enables the coding, decoding, and storage of sensory experience at various stages of the insect olfactory system. Individual parts of this system are capable of multiplexing memories at different timescales, and conversely, memory on a given timescale can be distributed across different parts of the circuit. Our sampling of the olfactory system emphasizes the diversity of memories, and the importance of understanding these memories in the context of computations performed by different parts of a sensory system.
Topics: Animals; Computer Simulation; Insecta; Memory; Models, Biological; Olfactory Pathways; Sensory Receptor Cells; Smell; Time Factors
PubMed: 21632235
DOI: 10.1016/j.conb.2011.05.005 -
The Journal of Neuroscience : the... Jun 2008Learning of a particularly difficult olfactory-discrimination (OD) task results in acquisition of rule learning. This remarkable enhancement in learning capability is...
Learning of a particularly difficult olfactory-discrimination (OD) task results in acquisition of rule learning. This remarkable enhancement in learning capability is accompanied by long-term enhancement of synaptic connectivity between piriform cortex (PC) pyramidal neurons. Because successful performance in the OD task requires integration of information about the identity and also about the reward value of odors, it is likely that a higher-order brain area would also be involved in rule learning acquisition and maintenance. The anterior PC (APC) receives a strong ascending input from the olfactory bulb, carrying information regarding olfactory cues in the environment. It also receives substantial descending input from the orbitofrontal cortex (OFC), which is thought to play an important role in encoding the predictive value of odor stimuli. Using in vivo recordings of evoked field postsynaptic potentials, we characterized the physiological properties of projections to APC from the OFC and examined whether descending and ascending synaptic inputs to the piriform cortex are modified after OD learning. We show that enhanced learning capability is accompanied by long-term enhancement of synaptic transmission in both the descending and ascending inputs. Long-term synaptic enhancement is not accompanied by modifications in paired-pulse facilitation, indicating that such modifications are likely postsynaptic. Predisposition for long-term potentiation induction was affected by previous learning, and surprisingly also by previous exposure to the odors and training apparatus. These data suggest that enhanced connectivity between the APC and its input sources is required for OD rule learning.
Topics: Animals; Discrimination Learning; Learning; Male; Neuronal Plasticity; Olfactory Bulb; Olfactory Pathways; Prefrontal Cortex; Pyramidal Cells; Rats; Rats, Sprague-Dawley; Smell; Synaptic Transmission; Time; Time Factors
PubMed: 18579740
DOI: 10.1523/JNEUROSCI.0178-08.2008 -
Learning & Memory (Cold Spring Harbor,... Oct 2011The nematode Caenorhabditis elegans (C. elegans) adult hermaphrodite has 302 invariant neurons and is suited for cellular and molecular studies on complex behaviors...
The nematode Caenorhabditis elegans (C. elegans) adult hermaphrodite has 302 invariant neurons and is suited for cellular and molecular studies on complex behaviors including learning and memory. Here, we have developed protocols for classical conditioning of worms with 1-propanol, as a conditioned stimulus (CS), and hydrochloride (HCl) (pH 4.0), as an unconditioned stimulus (US). Before the conditioning, worms were attracted to 1-propanol and avoided HCl in chemotaxis assay. In contrast, after massed or spaced training, worms were either not attracted at all to or repelled from 1-propanol on the assay plate. The memory after the spaced training was retained for 24 h, while the memory after the massed training was no longer observable within 3 h. Worms pretreated with transcription and translation inhibitors failed to form the memory by the spaced training, whereas the memory after the massed training was not significantly affected by the inhibitors and was sensitive to cold-shock anesthesia. Therefore, the memories after the spaced and massed trainings can be classified as long-term memory (LTM) and short-term/middle-term memory (STM/MTM), respectively. Consistently, like other organisms including Aplysia, Drosophila, and mice, C. elegans mutants defective in nmr-1 encoding an NMDA receptor subunit failed to form both LTM and STM/MTM, while mutations in crh-1 encoding the CREB transcription factor affected only the LTM.
Topics: Animals; Animals, Genetically Modified; Caenorhabditis elegans; Caenorhabditis elegans Proteins; Conditioning, Classical; Learning; Memory, Long-Term; Polymerase Chain Reaction; Smell
PubMed: 21960709
DOI: 10.1101/lm.2224411 -
Brain and Behavior Apr 2023In patients with mild cognitive impairment, pathological changes begin in the amygdala (AMG) and hippocampus (HI), especially in the parahippocampal gyrus and entorhinal...
INTRODUCTION
In patients with mild cognitive impairment, pathological changes begin in the amygdala (AMG) and hippocampus (HI), especially in the parahippocampal gyrus and entorhinal cortex (ENT). These areas play an important role in olfactory detection and recognition. It is important to understand how subtle signs of olfactory disability relate to the functions of the above-mentioned regions, as well as the orbitofrontal cortex (OFC). In this study, we evaluated brain activation using functional magnetic resonance imaging (fMRI), performed during the presentation of olfactory stimuli (classified as "normal odors" not inducing memory retrieval), and investigated the relationships of the blood oxygen level-dependent (BOLD) signal with olfactory detection and recognition abilities in healthy elderly subjects.
METHODS
Twenty-four healthy elderly subjects underwent fMRI during olfaction, and raw mean BOLD signals were extracted from regions of interest, including bilateral regions (AMG, HI, parahippocampus, and ENT) and orbitofrontal subregions (frontal inferior OFC, frontal medial OFC, frontal middle OFC, and frontal superior OFC). Multiple regression and path analyses were conducted to understand the roles of these areas in olfactory detection and recognition.
RESULTS
Activation of the left AMG had the greatest impact on olfactory detection and recognition, while the ENT, parahippocampus, and HI acted as a support system for AMG activation. Less activation of the right frontal medial OFC was associated with good olfactory recognition. These findings improve our understanding of the roles of limbic and prefrontal regions in olfactory awareness and identification in elderly individuals.
CONCLUSION
Functional decline of the ENT and parahippocampus crucially impacts olfactory recognition. However, AMG function may compensate for deficits through connections with frontal regions.
Topics: Humans; Aged; Odorants; Amygdala; Brain; Smell; Recognition, Psychology; Magnetic Resonance Imaging
PubMed: 36897168
DOI: 10.1002/brb3.2956