Associative Learning Research Articles

Formation and retrieval of cell assemblies in a biologically realistic spiking neural network model of area CA3 in the mouse hippocampus

The hippocampal formation is critical for episodic memory, with area Cornu Ammonis 3 (CA3) a necessary substrate for auto-associative pattern completion. Recent theoretical and experimental evidence suggests that the formation and retrieval of cell assemblies enable these functions. Yet, how cell assemblies are formed and retrieved in a full-scale spiking neural network (SNN) of CA3 that incorporates the observed diversity of neurons and connections within this circuit is not well understood. Here, we demonstrate that a data-driven SNN model quantitatively reflecting the neuron type-specific population sizes, intrinsic electrophysiology, connectivity statistics, synaptic signaling, and long-term plasticity of the mouse CA3 is capable of robust auto-association and pattern completion via cell assemblies. Our results show that a broad range of assembly sizes could successfully and systematically retrieve patterns from heavily incomplete or corrupted cues after a limited number of presentations. Furthermore, performance was robust with respect to partial overlap of assemblies through shared cells, substantially enhancing memory capacity. These novel findings provide computational evidence that the specific biological properties of the CA3 circuit produce an effective neural substrate for associative learning in the mammalian brain.

The ventral tegmental area dopamine to basolateral amygdala projection supports acquisition of cocaine self-administration

Dopamine signaling in the amygdala is known to play a role in associative learning and memory, including the process of learning to associate environmental cues with the reinforcing properties of drugs like cocaine. Evidence suggests that the ventral tegmental area (VTA) dopamine (DA) projection specifically to the basolateral amygdala (BLA) participates in establishing cocaine-cue associations that can promote later craving- and relapse-like responses to the cue alone. In order to further investigate the specific role of VTA-BLA projections in cocaine-reinforced learning, we used chemogenetics to manipulate VTA DA inputs to the BLA during cocaine self-administration, cue- and cocaine-primed reinstatement, and conditioned place preference. We found inhibiting DA input to the BLA during cocaine self-administration inhibited acquisition and weakened the ability of the previously cocaine-paired cue to elicit cocaine-seeking, while acutely inhibiting the pathway on the day of cue-induced reinstatement testing had no effect. Conversely, exciting the projection during self-administration boosted the salience of the cocaine-paired cue as indicated by enhanced responding during cue-induced reinstatement. Importantly, interfering with DA input to the BLA had no impact on the ability of cocaine to elicit a place preference or induce reinstatement in response to a priming cocaine injection. Overall, we show that manipulation of projections underlying DA signaling in the BLA may be useful for developing therapeutic interventions for substance use disorders.

Looming stimuli reliably drive innate defensive responses in male rats, but not learned defensive responses

Survival relies on an organism's intrinsic ability to instinctively react to stimuli such as food, water, and threats, ensuring the fundamental ability to feed, drink, and avoid danger even in the absence of prior experience. These natural, unconditioned stimuli can also facilitate associative learning, where pairing them consistently with neutral cues will elicit responses to these cues. Threat conditioning, a well-explored form of associative learning, commonly employs painful electric shocks, mimicking injury, as unconditioned stimuli. It remains elusive whether actual injury or pain is necessary for effective learning, or whether the threat of harm is sufficient. Approaching predators create looming shadows and sounds, triggering strong innate defensive responses like escape and freezing. This study investigates whether visual looming stimuli can induce learned freezing or learned escape responses to a conditioned stimulus in male rats. Surprisingly, pairing a neutral tone with a looming stimulus only weakly evokes learned defensive responses, in contrast to the strong responses observed when the looming stimulus is replaced by a shock. This dissociation sheds light on the boundaries for learned defensive responses thereby impacting our comprehension of learning processes and defensive strategies.

Deleterious effect of social instability on broiler chicken learning abilities and behaviour

Broiler chickens are reared in very large groups and are submitted to repeated encounters with unknown conspecifics. Our aim was to assess the consequences of these encounters on broiler chickens learning abilities, social behaviour and emotional reactivity. Groups of 5 male medium-growing broiler chickens (JA 957) were reared under stable or unstable social conditions (n=16 groups in each condition). Under the unstable conditions, the 5 birds of the groups changed every 3–4 days from 1 to 52 days of age. Broiler chickens were tested in an associative learning task (conditioned place preference) between 14 and 18 days of age. A highly palatable food (mealworms) was delivered in a particular environment with coloured stripes and preference for this environment was then tested. Social behaviours were analysed between 21 and 43 days of age. Emotional reactivity of the birds when faced with novelty (reactivity to unknown food, object and human) was assessed at the end of the rearing period (46–51 days of age). Only birds from the stable condition were able to associate the palatable food to the environment in which it was delivered (p = 0.02). Furthermore, these birds had a higher social proximity than those from the unstable condition (p < 0.01) and showed less aggressive interactions such as aggressive pecking (p = 0.06), threat (p < 0.01) or facing each other with wing flapping in front of another bird (p = 0.03). The social conditions tested had no significant effect on their emotional reactivity. Our results evidenced that chickens exposed to social instability have some learning abilities impaired compared to chickens maintained in stable social conditions. In addition, social instability increases aggressive interactions between conspecifics, while social stability favours bird proximity. In conclusion, being reared in unstable social conditions likely impairs bird adaptation to their rearing environment and increases deleterious consequences of aggressive interactions with conspecifics.

B - 115 How Training Conditions Impact Performance on a Theoretically-Derived Learning Instrument

Abstract Objective Few neuropsychological measures were developed using an explicit theory that accounts for individual performance. We developed a novel associative learning measure to address this limitation and investigated whether training conditions could influence accuracy and response time. Methods Fifty young, community-dwelling adult participants completed the novel relational learning task, which explicitly trained two stimulus pairs (A- &amp;gt; B, A- &amp;gt; C) and involved a single common stimulus. Participants identify six unique relationships between stimuli: trained relations (A- &amp;gt; B, A- &amp;gt; C), mutually entailed relations (B- &amp;gt; A, C- &amp;gt; A), and combinatorial relations (B- &amp;gt; C, C- &amp;gt; B). Participants were randomly assigned to a congruent (A is opposite B, A is opposite C) or incongruent (A is opposite B, B is the same as C) training condition and completed the procedure when stimuli were observably (e.g., color-coded shapes) or arbitrarily related (e.g., letters). Results Comparisons of accuracy between training conditions using Bayesian independent samples t-tests found moderate evidence of no reliable difference between training groups when stimuli were observably related (BF01 = 3.4, δ = 0.06) and arbitrarily related (BF01 = 3.5, δ = 0.03). Comparisons of response time found strong evidence that participants took longer to identify relations when receiving incongruent training when the stimuli were visually related (BF10 = 38.8, δ = 0.9) but inconclusive evidence when the stimuli were arbitrarily related (BF10 = 1.5, δ = 0.49) (See Table 1). Conclusion These findings suggest that manipulating training conditions does not appreciably impact the ability to identify relationships between stimuli accurately. However, training appears to increase the response time needed to identify visibly related stimuli accurately. While this is a promising theoretically-derived learning paradigm, further research is required for validation in clinical practice.

Learning motivation of college students in multimedia environment with machine learning models

As the main force of higher education, ensuring the learning status and quality of college students is undoubtedly an important task in the education industry. Analyzing their learning motivation can provide a good understanding of their learning status. Especially in the new educational environment supported by multimedia technology, efficient and convenient learning channels can eliminate students' concerns about educational facilities and instead strengthen the analysis of learning motivation in other aspects. As part of our comprehensive study of learning motivation, we draw on established learning theories, such as reinforcement theory, associative learning, and self-determination theory. Applying such learning theories encourages positive reinforcement, establishes constructive relationships with learning, and nurtures competence and autonomy. This article believed that using machine learning models to predict students' grades or behaviours and analyze their learning motivation is a good approach. Moreover, this article also tested the prediction accuracy by setting different improved random forest model runs, and concluded that the more runs, the higher the accuracy. Especially when the runs reached 100, the accuracy reached 99.98 %.

Multimodal assessment of the role of intolerance of uncertainty in fear acquisition and extinction

Personality traits linked to internalizing disorders influence the way we develop fears, but also how we regain a sense of safety. In the present study, we investigated the effect of intolerance of uncertainty (IU) on defensive responses using a differential fear conditioning protocol with an extinction phase. The conditioned stimulus was associated with an aversive sound (90 dB) in 75 % of the presentations during acquisition. A final sample of 176 participants completed the experiment. We measured self-reports of associative (expectancy of the unconditioned stimulus in acquisition) and evaluative learning (arousal and valence), and both physiological (skin conductance response) and electrocortical responses (steady-state visually evoked potentials, ssVEPs; late positive potentials, LPP) to the conditioned stimuli. Our results show that IU's impact is limited, with no effect in both acquisition and extinction. These findings emphasize the necessity of large samples in research on inter-individual differences and contribute to our understanding of how IU may or may not be involved in fear and safety learning processes considering multiple aspects of fear responding.

Reinforcement learning as a robotics-inspired framework for insect navigation: from spatial representations to neural implementation.

Bees are among the master navigators of the insect world. Despite impressive advances in robot navigation research, the performance of these insects is still unrivaled by any artificial system in terms of training efficiency and generalization capabilities, particularly considering the limited computational capacity. On the other hand, computational principles underlying these extraordinary feats are still only partially understood. The theoretical framework of reinforcement learning (RL) provides an ideal focal point to bring the two fields together for mutual benefit. In particular, we analyze and compare representations of space in robot and insect navigation models through the lens of RL, as the efficiency of insect navigation is likely rooted in an efficient and robust internal representation, linking retinotopic (egocentric) visual input with the geometry of the environment. While RL has long been at the core of robot navigation research, current computational theories of insect navigation are not commonly formulated within this framework, but largely as an associative learning process implemented in the insect brain, especially in the mushroom body (MB). Here we propose specific hypothetical components of the MB circuit that would enable the implementation of a certain class of relatively simple RL algorithms, capable of integrating distinct components of a navigation task, reminiscent of hierarchical RL models used in robot navigation. We discuss how current models of insect and robot navigation are exploring representations beyond classical, complete map-like representations, with spatial information being embedded in the respective latent representations to varying degrees.

How labels shape visuocortical processing in infants.

The current study examined the extent to which labels shape visuocortical processing during the first year of life during a brief (~6-min) associative learning task. Images of computer-generated artificial objects were paired with either individual-level (e.g., Jimmy, Boris) or category-level labels (e.g., Hitchel) while event-related potentials were recorded in response to the onset of the visual stimulus in 6- (n=41), 9- (n=27), and 12-month-old (n=28) infants. Analyses examined experience-dependent visuocortical changes within and across trials, label conditions, and ages. Overall, results demonstrate that infants deploy greater visuocortical resources during the first half of associative learning trials and to stimuli paired with category-level relative to individual-level labels. Waveform morphologies also differed between stimuli paired with individual- and category-level labels and across the age groups, with more complex deflections and amplitude differences between label type at 9- and 12-month-olds, but not 6-month-old infants. The present results highlight the importance of associative learning during infancy and suggest that category- versus individual-level labels differentially direct infant attention and visuocortical processing.

Analysis of fast calcium dynamics of honey bee olfactory coding

Odour processing exhibits multiple parallels between vertebrate and invertebrate olfactory systems. Insects, in particular, have emerged as relevant models for olfactory studies because of the tractability of their olfactory circuits. Here, we used fast calcium imaging to track the activity of projection neurons in the honey bee antennal lobe (AL) during olfactory stimulation at high temporal resolution. We observed a heterogeneity of response profiles and an abundance of inhibitory activities, resulting in various response latencies and stimulus-specific post-odour neural signatures. Recorded calcium signals were fed to a mushroom body (MB) model constructed implementing the fundamental features of connectivity between olfactory projection neurons, Kenyon cells (KC), and MB output neurons (MBON). The model accounts for the increase of odorant discrimination in the MB compared to the AL and reveals the recruitment of two distinct KC populations that represent odorants and their aftersmell as two separate but temporally coherent neural objects. Finally, we showed that the learning-induced modulation of KC-to-MBON synapses can explain both the variations in associative learning scores across different conditioning protocols used in bees and the bees' response latency. Thus, it provides a simple explanation of how the time contingency between the stimulus and the reward can be encoded without the need for time tracking. This study broadens our understanding of olfactory coding and learning in honey bees. It demonstrates that a model based on simple MB connectivity rules and fed with real physiological data can explain fundamental aspects of odour processing and associative learning.

Chronic social defeat stress gives rise to social avoidance through fear learning

Chronic social defeat stress (CSDS), a widely used rodent model of stress, reliably leads to decreased social interaction in stress susceptible animals. Here, we investigate a role for fear learning in this response using male 129 Sv/Ev mice, a strain that is more vulnerable to CSDS than the commonly used C57BL/6 strain. We first demonstrate that defeated 129 Sv/Ev mice avoid a CD-1 mouse, but not a conspecific, indicating that motivation to socialize is intact in this strain. CD-1 avoidance is characterized by approach behavior that results in running in the opposite direction, activity that is consistent with a threat response. We next test whether CD-1 avoidance is subject to the same behavioral changes found in traditional models of Pavlovian fear conditioning. We find that associative learning occurs across 10 days CSDS, with defeated mice learning to associate the color of the CD-1 coat with threat. This leads to the gradual acquisition of avoidance behavior, a conditioned response that can be extinguished with 7 days of repeated social interaction testing (5 tests/day). Pairing a CD-1 with a tone leads to second-order conditioning, resulting in avoidance of an enclosure without a social target. Finally, we show that social interaction with a conspecific is a highly variable response in defeated mice that may reflect individual differences in generalization of fear to other social targets. Our data indicate that fear conditioning to a social target is a key component of CSDS, implicating the involvement of fear circuits in social avoidance.

The mesolimbic system and the loss of higher order network features in schizophrenia when learning without reward.

Schizophrenia is characterized by a loss of network features between cognition and reward sub-circuits (notably involving the mesolimbic system), and this loss may explain deficits in learning and cognition. Learning in schizophrenia has typically been studied with tasks that include reward related contingencies, but recent theoretical models have argued that a loss of network features should be seen even when learning without reward. We tested this model using a learning paradigm that required participants to learn without reward or feedback. We used a novel method for capturing higher order network features, to demonstrate that the mesolimbic system is heavily implicated in the loss of network features in schizophrenia, even when learning without reward. fMRI data (Siemens Verio 3T) were acquired in a group of schizophrenia patients and controls (n=78; 46 SCZ, 18 ≤ Age ≤ 50) while participants engaged in associative learning without reward-related contingencies. The task was divided into task-active conditions for encoding (of associations) and cued-retrieval (where the cue was to be used to retrieve the associated memoranda). No feedback was provided during retrieval. From the fMRI time series data, network features were defined as follows: First, for each condition of the task, we estimated 2nd order undirected functional connectivity for each participant (uFC, based on zero lag correlations between all pairs of regions). These conventional 2nd order features represent the task/condition evoked synchronization of activity between pairs of brain regions. Next, in each of the patient and control groups, the statistical relationship between all possible pairs of 2nd order features were computed. These higher order features represent the consistency between all possible pairs of 2nd order features in that group and embed within them the contributions of individual regions to such group structure. From the identified inter-group differences (SCZ ≠ HC) in higher order features, we quantified the respective contributions of individual brain regions. Two principal effects emerged: 1) SCZ were characterized by a massive loss of higher order features during multiple task conditions (encoding and retrieval of associations). 2) Nodes in the mesolimbic system were over-represented in the loss of higher order features in SCZ, and notably so during retrieval. Our analytical goals were linked to a recent circuit-based integrative model which argued that synergy between learning and reward circuits is lost in schizophrenia. The model's notable prediction was that such a loss would be observed even when patients learned without reward. Our results provide substantial support for these predictions where we observed a loss of network features between the brain's sub-circuits for a) learning (including the hippocampus and prefrontal cortex) and b) reward processing (specifically constituents of the mesolimbic system that included the ventral tegmental area and the nucleus accumbens. Our findings motivate a renewed appraisal of the relationship between reward and cognition in schizophrenia and we discuss their relevance for putative behavioral interventions.

Assessment of positive experiences using associative learning in chickens

To determine whether differences in positive experiences can influence associative learning ability, 2 tasks were conducted with 90 laying hens at the peak of the laying period. The selected hens were reared in a larger flock under the same housing conditions without perches, so they had the same rearing experiences and were moved to either enriched cages or to the floor system at 16 wk of age. They belonged to 3 breeds (Slovenian barred hen: Ba; brown hen: Br; silver hen, S), with 30 hens per breed. The predictor signal, the sound of a clicker, with a 3-second delayed reinforcer (commercial layer feed) was used to mark the desired behaviour (pecking for feed). Hens that associated feed with a clicker (85.06%) were taught 2 tasks, the colour discrimination task (CD) and the target following task (TF). In the CD, the hens had to discriminate between yellow, red and blue colors and peck at a yellow magnet only. In the TF, the desired behaviour was to follow a target, a purple ball on a stick, from 1 perch to another and peck it at the end of the perch. The main results of the hens associating the signal with feed were that the Ba hens learned faster than the S hens (P = 0.006) and required fewer clicker sounds than the Br hens in the CD (P = 0.003). Floor hens that completed CD or TF or both took less time to complete the task (CD, P = 0.03, TF, P = 0.06; both tasks, P = 0.02) or with fewer clicker sounds (CD task; P = 0.02) than cage hens. Although these results suggest that Ba hens and floor hens showed better associate learning performance, probably because they perceived their environment as more rewarding and thus potentially more positive, caution is needed in interpretation considering social experiences and that the ability to perch and the ability to move quickly on a perch can be confounded in TF and both tasks can be confounded with foraging ability.

The influence of repetitive thoughts of CS-US pairing on expectancy learning and evaluative conditioning: a fundamental study.

Repetitive thinking is a common phenomenon, also implicated in a variety of mental disorders. The content of repetitive thoughts can take the form of prediction of aversive events (in worry) or evoking negatively valenced information (in rumination), for instance. Investigating the influence of repetitive thinking through the lens of associative learning could help deepen our understanding of the mechanisms involved in its effects.In two experiments, non-clinical participants were exposed to CS-US pairings with the aim of creating non-threatening expectancy learning (Experiment 1) or evaluative conditioning (Experiment 2). After each conditioning trial, participants were instructed to initiate repetitive thoughts about the pairing (i.e. rehearse) or follow control instructions.Experiment 1 (N = 64) showed that such intervention strengthen the association between the mental representations of the CS and the US, leading to a stronger US expectancy in response to the CS. In Experiment 2 (N = 107), an evaluative conditioning effect was observed; however, it was not influenced by instructions.The study demonstrated that simulated repetitive thinking strengthens the CS-US association and leads to greater US expectancy in expectancy learning, despite appearing not to influence the evaluative conditioning effect. The potential implications of these findings on repetitive thinking are discussed.

Emotional Overshadowing: Pleasant and Unpleasant Cues Overshadow Neutral Cues in Human Associative Learning.

The online version contains supplementary material available at 10.1007/s42761-024-00270-0.

Intentional learning establishes multiple attentional sets that simultaneously guide attention.

One of the key human cognitive capabilities is to extract regularities from the environment to guide behavior. An attentional set for a target feature can be established through statistical learning of probabilistic target associations; however, whether an array of attentional sets of predictive target features can be established during intentional learning, and how they might guide attention, is not known yet. To address these questions, we had human observers perform a visual search task where we instructed them to try to use color to find their target shape. We structured the task with a fine-grained statistical regularity such that the target shapes appeared in different colors with five unique probabilities (i.e., 33%, 26%, 19%, 12%, and 5%) while we recorded their electroencephalogram. Observers rapidly learned these regularities, evidenced by being faster to report targets that appeared in higher probability colors. These effects were not due to unequal sample sizes or simple feature priming. More importantly, equivalent speeding across a set of high-probability colors suggests that the brain was driving attention to multiple targets simultaneously. Our electrophysiological results showed larger amplitude N2 posterior contralateral component, indexing perceptual attention, and late positive complex (LPC) component, indexing postperceptual processes, for targets paired with high-probability colors. These electrophysiological data suggest that the learned attentional sets change both perceptual selection and how postperceptual decisions are made. In sum, we show that multiple attentional sets can be established during intentional learning that accompanies general task acquisition and that these attentional sets can simultaneously guide attention by enhancing both perceptual attention and postperceptual processes. (PsycInfo Database Record (c) 2024 APA, all rights reserved).

Mechanical Neural Networks with Explicit and Robust Neurons.

Mechanical computing provides an information processing method to realize sensing-analyzing-actuation integrated mechanical intelligence and, when combined with neural networks, can be more efficient for data-rich cognitive tasks. The requirement of solving implicit and usually nonlinear equilibrium equations of motion in training mechanical neural networks makes computation challenging and costly. Here, an explicit mechanical neuron is developed of which the response can be directly determined without the need of solving equilibrium equations. A training method is proposed to ensure the robustness of the neuron, i.e., insensitivity to defects and perturbations. The explicitness and robustness of the neurons facilitate the assembly of various network structures. Two exemplified networks, a robust mechanical convolutional neural network and a mechanical recurrent neural network with long short-term memory capabilities for associative learning, are experimentally demonstrated. The introduction of the explicit and robust mechanical neuron streamlines the design of mechanical neural networks fulfilling robotic matter with a level of intelligence.

Ellagic acid improves the symptoms of early-onset Alzheimer's disease: Behavioral and physiological correlates

Oryza sativa is a globally recognized staple food, rich in essential phyto-phenolic compounds such as γ-Oryzanol (OZ), Ferulic acid (FA), and Ellagic acid (EA). These phytochemicals are known for their potential to beneficially modulate molecular biochemistry. The present investigation aimed to evaluate the neuroprotective and cognitive enhancement effects of Oryza sativa phyto-phenolics in a model of early-onset Alzheimer's disease (EOAD) induced by Aβ (1-42) in animals. In-silico studies suggested that FA, OZ, and EA have target specificity for Aβ, with EA being further selected based on its potent in-vitro Aβ anti-aggregatory effects for exploring neurodegenerative conditions. The in-vivo experiments demonstrated that EA exerts therapeutic effects in Aβ-induced EOAD, modulating both biochemical and behavioral outcomes. EA treatment at two dose levels, EA70 and EA140 (70 μM and 140 μM, respectively, administered i.c.v.), significantly counteracted Aβ aggregation and modulated the Ca2⁺/Calpain/GSK-3β/CDK5 signaling pathways, exhibiting anti-tauopathy effects. Additionally, EA was shown to exert anti-inflammatory effects by preventing astroglial activation, modulating FAIM-L expression, and protecting against TNF-α-induced apoptotic signals. Moreover, the neuromodulatory effects of EA were attributed to the regulation of CREB levels, Dnm-1 expression, and synaptophysin levels, thereby enhancing LTP and synaptic plasticity. EA also induced beneficial cytological and behavioral changes, improving both long-term and short-term spatial memory as well as associative learning behavior in the animal model, which underscores its cognitive enhancement properties.

Midkine is upregulated in the hippocampus following bothspatial and olfactory reward association learning and enhances memory.

Hippocampal neuronal plasticity is a fundamental process underpinning learning and memory formation and requiring elaborate molecular mechanisms that result in the dynamic remodelling of synaptic connectivity. The neurotrophic properties of midkine (Mdk) have been implicated in the development and repair of the nervous system, while Mdk knockout resulted in deficits in the formation of certain types of memory. The role of Mdk in the process of memory-associated neuronal plasticity, however, remains poorly understood. We investigated the learning-induced regulation of Mdk in spatial navigation and association learning using the water maze and the odour reward association learning paradigms, characterising a temporal profile of Mdk protein expression post-learning. Both learning events revealed similar patterns of upregulation of expression of the protein in the rat hippocampal dentate gyrus, which were rapid and transient. Moreover, administration of recombinant Mdk during the endogenous Mdk upregulation following learning enhanced memory in the water maze task revealing a pro-cognitive action of Mdk. We further show that, within the adult hippocampus, Mdk mRNA is predominantly expressed in granular and pyramidal neurons and that hippocampal neuronal Mdk expression is regulated by the canonical plasticity-associated neurotransmitter glutamate. Finally, we confirm that the positive action of Mdk on neurite outgrowth previously noted in cortical and cerebellar neurons extends to hippocampal neurons. Together, our findings suggest a role for Mdk in glutamate-mediated hippocampal neuronal plasticity important for long-term memory consolidation.

Independent operations of appetitive and aversive conditioning systems lead to simultaneous production of conflicting memories in an insect.

Pavlovian conditioning is a ubiquitous form of associative learning that enables animals to remember appetitive and aversive experiences. Animals possess appetitive and aversive conditioning systems that memorize and retrieve appetitive and aversive experiences. Here, we addressed a question of whether integration of competing appetitive and aversive information takes place during the encoding of the experience or during memory retrieval. We developed novel experimental procedures to address this question using crickets (Gryllus bimaculatus), which allowed selective blockade of the expression of appetitive and aversive memories by injecting octopamine and dopamine receptor antagonists. We conditioned an odour (conditioned stimulus 1, CS1) with water and then with sodium chloride solution. At 24 h after conditioning, crickets retained both appetitive and aversive memories, and the memories were integrated to produce a conditioned response (CR). Importantly, when a visual pattern (CS2) was conditioned with CS1, appetitive and aversive memories formed simultaneously. This indicates that appetitive and aversive second-order conditionings are achieved at the same time. The memories were integrated for producing a conditioned response. We conclude that appetitive and aversive conditioning systems operate independently to form parallel appetitive and aversive memories, which compete to produce learned behaviour in crickets.