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Current Opinion in Insect Science Jun 2023Trace conditioning is a form of Pavlovian learning in which the conditioned stimulus (CS) and the unconditioned stimulus (US) are separated by a temporal gap. Insects... (Review)
Review
Trace conditioning is a form of Pavlovian learning in which the conditioned stimulus (CS) and the unconditioned stimulus (US) are separated by a temporal gap. Insects learn trace associations of variable nature (appetitive, aversive) and involving CSs of different sensory modalities (olfactory, visual). The accessibility of the insect neural system in behaving animals allowed identifying neural processes driving trace conditioning: the existence of prolonged neural responses to the CS after stimulus offset and the anticipation of US responses during the free-stimulus gap. Specific brain structures, such as the mushroom bodies seem to be allocated to this learning form. Here, we posit that a further component facilitating trace conditioning in insects relates to neuromodulatory mechanisms underlying enhanced attention. We thus propose a model based on different types of mushroom-body neurons, which provides a cognitive account of trace conditioning in insects.
Topics: Animals; Learning; Insecta; Smell; Brain; Cognition
PubMed: 37044245
DOI: 10.1016/j.cois.2023.101034 -
Proceedings of the National Academy of... Mar 2018Olfaction is an important sensory modality driving fundamental behaviors. During odor-dependent learning, a positive value is commonly assigned to an odorant, and...
Olfaction is an important sensory modality driving fundamental behaviors. During odor-dependent learning, a positive value is commonly assigned to an odorant, and multiple forms of plasticity are involved when such odor-reward associations are formed. In rodents, one of the mechanisms underlying plasticity in the olfactory bulb consists in recruiting new neurons daily throughout life. However, it is still unknown whether adult-born neurons might participate in encoding odor value. Here, we demonstrate that exposure to reward-associated odors specifically increases activity of adult-born neurons but not preexisting neurons. Remarkably, adult-born neuron activation during rewarded odor presentation heightens discrimination learning and enhances the ability to update the odor value during reversal association. Moreover, in some cases, activation of this interneuron population can trigger olfactory learning without sensory stimulation. Taken together, our results show a specific involvement of adult-born neurons in facilitating odor-reward association during adaptive learning.
Topics: Animals; Discrimination Learning; Female; Male; Models, Neurological; Odorants; Olfactory Bulb; Olfactory Receptor Neurons; Rats; Reward; Smell
PubMed: 29467284
DOI: 10.1073/pnas.1716400115 -
Scientific Reports Jun 2023During the olfactory perception process, our olfactory receptors are thought to recognize specific chemical features. These features may contribute towards explaining...
During the olfactory perception process, our olfactory receptors are thought to recognize specific chemical features. These features may contribute towards explaining our crossmodal perception. The physicochemical features of odors can be extracted using an array of gas sensors, also known as an electronic nose. The present study investigates the role that the physicochemical features of olfactory stimuli play in explaining the nature and origin of olfactory crossmodal correspondences, which is a consistently overlooked aspect of prior work. Here, we answer the question of whether the physicochemical features of odors contribute towards explaining olfactory crossmodal correspondences and by how much. We found a similarity of 49% between the perceptual and the physicochemical spaces of our odors. All of our explored crossmodal correspondences namely, the angularity of shapes, smoothness of textures, perceived pleasantness, pitch, and colors have significant predictors for various physicochemical features, including aspects of intensity and odor quality. While it is generally recognized that olfactory perception is strongly shaped by context, experience, and learning, our findings show that a link, albeit small (6-23%), exists between olfactory crossmodal correspondences and their underlying physicochemical features.
Topics: Smell; Olfactory Perception; Electronic Nose; Emotions; Learning
PubMed: 37391587
DOI: 10.1038/s41598-023-37770-1 -
Malaria Journal Jan 2012Memory and learning are critical aspects of the ecology of insect vectors of human pathogens because of their potential effects on contacts between vectors and their...
BACKGROUND
Memory and learning are critical aspects of the ecology of insect vectors of human pathogens because of their potential effects on contacts between vectors and their hosts. Despite this epidemiological importance, there have been only a limited number of studies investigating associative learning in insect vector species and none on Anopheline mosquitoes.
METHODS
A simple behavioural assays was developed to study visual and olfactory associative learning in Anopheles gambiae, the main vector of malaria in Africa. Two contrasted membrane qualities or levels of blood palatability were used as reinforcing stimuli for bi-directional conditioning during blood feeding.
RESULTS
Under such experimental conditions An. gambiae females learned very rapidly to associate visual (chequered and white patterns) and olfactory cues (presence and absence of cheese or Citronella smell) with the reinforcing stimuli (bloodmeal quality) and remembered the association for up to three days. Associative learning significantly increased with the strength of the conditioning stimuli used. Importantly, learning sometimes occurred faster when a positive reinforcing stimulus (palatable blood) was associated with an innately preferred cue (such as a darker visual pattern). However, the use of too attractive a cue (e.g. Shropshire cheese smell) was counter-productive and decreased learning success.
CONCLUSIONS
The results address an important knowledge gap in mosquito ecology and emphasize the role of associative memory for An. gambiae's host finding and blood-feeding behaviour with important potential implications for vector control.
Topics: Animals; Anopheles; Association Learning; Disease Vectors; Female; Smell; Vision, Ocular
PubMed: 22284012
DOI: 10.1186/1475-2875-11-27 -
The Journal of Neuroscience : the... May 2018Associative fear learning produces fear toward the conditioned stimulus (CS) and often generalization, the expansion of fear from the CS to similar, unlearned stimuli....
Associative fear learning produces fear toward the conditioned stimulus (CS) and often generalization, the expansion of fear from the CS to similar, unlearned stimuli. However, how fear learning affects early sensory processing of learned and unlearned stimuli in relation to behavioral fear responses to these stimuli remains unclear. We subjected male and female mice expressing the fluorescent calcium indicator GCaMP3 in olfactory bulb mitral and tufted cells to a classical olfactory fear conditioning paradigm. We then used awake, calcium imaging to quantify learning-induced changes in glomerular odor responses, which constitute the first site of olfactory processing in the brain. The results demonstrate that odor-shock pairing nonspecifically enhances glomerular odor representations in a learning-dependent manner and increases representational similarity between the CS and nonconditioned odors, potentially priming the system toward generalization of learned fear. Additionally, CS-specific glomerular enhancements remain even when associative learning is blocked, suggesting two separate mechanisms lead to enhanced glomerular responses following odor-shock pairings. In the olfactory bulb (OB), odors are uniquely coded in a spatial map that represents odor identity, making the OB a unique model system for investigating how learned fear alters sensory processing. Classical fear conditioning causes fear of the conditioned stimulus (CS) and of neutral stimuli, known as generalization. Combining fear conditioning with fluorescent calcium imaging of OB glomeruli, we found enhanced glomerular responses of the CS as well as neutral stimuli in awake mice, which mirrors fear generalization. We report that CS and neutral stimuli enhancements are, respectively, learning-independent and learning-dependent. Together, these results reveal distinct mechanisms leading to enhanced OB processing of fear-inducing stimuli and provide important implications for altered sensory processing in fear generalization.
Topics: Acoustic Stimulation; Anesthesia; Animals; Behavior, Animal; Brain Mapping; Conditioning, Classical; Fear; Female; Generalization, Psychological; Learning; Male; Mice; Odorants; Olfactory Bulb; Sensory Receptor Cells; Smell
PubMed: 29669746
DOI: 10.1523/JNEUROSCI.3559-17.2018 -
ELife Sep 2023How memories are used by the brain to guide future action is poorly understood. In olfactory associative learning in , multiple compartments of the mushroom body act in...
How memories are used by the brain to guide future action is poorly understood. In olfactory associative learning in , multiple compartments of the mushroom body act in parallel to assign a valence to a stimulus. Here, we show that appetitive memories stored in different compartments induce different levels of upwind locomotion. Using a photoactivation screen of a new collection of split-GAL4 drivers and EM connectomics, we identified a cluster of neurons postsynaptic to the mushroom body output neurons (MBONs) that can trigger robust upwind steering. These UpWind Neurons (UpWiNs) integrate inhibitory and excitatory synaptic inputs from MBONs of appetitive and aversive memory compartments, respectively. After formation of appetitive memory, UpWiNs acquire enhanced response to reward-predicting odors as the response of the inhibitory presynaptic MBON undergoes depression. Blocking UpWiNs impaired appetitive memory and reduced upwind locomotion during retrieval. Photoactivation of UpWiNs also increased the chance of returning to a location where activation was terminated, suggesting an additional role in olfactory navigation. Thus, our results provide insight into how learned abstract valences are gradually transformed into concrete memory-driven actions through divergent and convergent networks, a neuronal architecture that is commonly found in the vertebrate and invertebrate brains.
Topics: Animals; Wind; Learning; Drosophila; Smell; Neurons; Mushroom Bodies; Drosophila melanogaster
PubMed: 37721371
DOI: 10.7554/eLife.85756 -
Trends in Neurosciences Jan 2011In mammals, new neurons are recruited into restricted brain areas throughout life. Adult-born neurons produced in the subventricular zone of the lateral ventricle... (Review)
Review
In mammals, new neurons are recruited into restricted brain areas throughout life. Adult-born neurons produced in the subventricular zone of the lateral ventricle migrate rostrally towards the olfactory bulb. Although thousands of neurons reach this central structure every day, the functional impact of their integration into mature circuits remains a matter of debate. Recent investigations have revealed no striking sensory deficits per se when adult bulbar neurogenesis is challenged. However, some cognitive functions, such as perceptual learning and olfactory memory, are clearly impaired. In this review we highlight the role of network activity in shaping ongoing neurogenesis and, in turn, how the integration of adult-born neurons refines pre-existing network function, and consequently olfactory behavior.
Topics: Animals; Learning; Nerve Net; Neurogenesis; Neurons; Odorants; Olfactory Bulb; Smell
PubMed: 20980064
DOI: 10.1016/j.tins.2010.09.006 -
Current Opinion in Neurobiology Oct 2020Olfaction facilitates a large variety of animal behaviors such as feeding, mating, and communication. Recent work has begun to reveal the logic of odor transformations... (Review)
Review
Olfaction facilitates a large variety of animal behaviors such as feeding, mating, and communication. Recent work has begun to reveal the logic of odor transformations that occur throughout the olfactory system to form the odor percept. In this review, we describe the coding principles and mechanisms by which the piriform cortex and other olfactory areas encode three key odor features: odor identity, intensity, and valence. We argue that the piriform cortex produces a multiplexed odor code that allows non-interfering representations of distinct features of the odor stimulus to facilitate odor recognition and learning, which ultimately drives behavior.
Topics: Animals; Learning; Odorants; Olfactory Pathways; Olfactory Perception; Piriform Cortex; Smell
PubMed: 32422571
DOI: 10.1016/j.conb.2020.03.001 -
BMC Infectious Diseases Aug 2021The extraordinary olfactory sense of canines combined with the possibility to learn by operant conditioning enables dogs for their use in medical detection in a wide... (Review)
Review
The extraordinary olfactory sense of canines combined with the possibility to learn by operant conditioning enables dogs for their use in medical detection in a wide range of applications. Research on the ability of medical detection dogs for the identification of individuals with infectious or non-infectious diseases has been promising, but compared to the well-established and-accepted use of sniffer dogs by the police, army and customs for substances such as money, explosives or drugs, the deployment of medical detection dogs is still in its infancy. There are several factors to be considered for standardisation prior to deployment of canine scent detection dogs. Individual odours in disease consist of different volatile organic molecules that differ in magnitude, volatility and concentration. Olfaction can be influenced by various parameters like genetics, environmental conditions, age, hydration, nutrition, microbiome, conditioning, training, management factors, diseases and pharmaceuticals. This review discusses current knowledge on the function and importance of canines' olfaction and evaluates its limitations and the potential role of the dog as a biomedical detector for infectious and non-infectious diseases.
Topics: Animals; Dogs; Learning; Odorants; Smell
PubMed: 34412582
DOI: 10.1186/s12879-021-06523-8 -
Genes, Brain, and Behavior Feb 2022Foraging for food is an integral part of animal survival. In small insects and invertebrates, multisensory information and optimized locomotion strategies are used to... (Review)
Review
Foraging for food is an integral part of animal survival. In small insects and invertebrates, multisensory information and optimized locomotion strategies are used to effectively forage in patchy and complex environments. Here, the importance of olfactory cues for effective invertebrate foraging is discussed in detail. We review how odors are used by foragers to move toward a likely food source and the recent models that describe this sensory-driven behavior. We argue that smell serves a second function by priming an organism for the efficient exploitation of food. By appraising food odors, invertebrates can establish preferences and better adapt to their ecological niches, thereby promoting survival. The smell of food pre-prepares the gastrointestinal system and primes feeding motor programs for more effective ingestion as well. Optimizing resource utilization affects longevity and reproduction as a result, leading to drastic changes in survival. We propose that models of foraging behavior should include odor priming, and illustrate this with a simple toy model based on the marginal value theorem. Lastly, we discuss the novel techniques and assays in invertebrate research that could investigate the interactions between odor sensing and food intake. Overall, the sense of smell is indispensable for efficient foraging and influences not only locomotion, but also organismal physiology, which should be reflected in behavioral modeling.
Topics: Animals; Cues; Feeding Behavior; Invertebrates; Odorants; Smell
PubMed: 34978135
DOI: 10.1111/gbb.12793