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Nature Reviews. Neuroscience Mar 2020The dentate gyrus (DG) has a key role in hippocampal memory formation. Intriguingly, DG lesions impair many, but not all, hippocampus-dependent mnemonic functions,... (Review)
Review
The dentate gyrus (DG) has a key role in hippocampal memory formation. Intriguingly, DG lesions impair many, but not all, hippocampus-dependent mnemonic functions, indicating that the rest of the hippocampus (CA1-CA3) can operate autonomously under certain conditions. An extensive body of theoretical work has proposed how the architectural elements and various cell types of the DG may underlie its function in cognition. Recent studies recorded and manipulated the activity of different neuron types in the DG during memory tasks and have provided exciting new insights into the mechanisms of DG computational processes, particularly for the encoding, retrieval and discrimination of similar memories. Here, we review these DG-dependent mnemonic functions in light of the new findings and explore mechanistic links between the cellular and network properties of, and the computations performed by, the DG.
Topics: Animals; Dentate Gyrus; Discrimination Learning; Entorhinal Cortex; Humans; Memory Consolidation; Memory, Episodic; Mental Recall; Models, Neurological; Neurons
PubMed: 32042144
DOI: 10.1038/s41583-019-0260-z -
Neuroscience and Biobehavioral Reviews Jan 2020Every day we are bombarded by stimuli that must be assessed for their potential for harm or benefit. Once a stimulus is learned to predict harm, it can elicit fear... (Review)
Review
Every day we are bombarded by stimuli that must be assessed for their potential for harm or benefit. Once a stimulus is learned to predict harm, it can elicit fear responses. Such learning can last a lifetime but is not always beneficial for an organism. For an organism to thrive in its environment, it must know when to engage in defensive, avoidance behaviors and when to engage in non-defensive, approach behaviors. Fear should be suppressed in situations that are not dangerous: when a novel, innocuous stimulus resembles a feared stimulus, when a feared stimulus no longer predicts harm, or when there is an option to avoid harm. A cardinal feature of anxiety disorders is the inability to suppress fear adaptively. In PTSD, for instance, learned fear is expressed inappropriately in safe situations and is resistant to extinction. In this review, we discuss mechanisms of suppressing fear responses during stimulus discrimination, fear extinction, and active avoidance, focusing on the well-studied tripartite circuit consisting of the amygdala, medial prefrontal cortex and hippocampus.
Topics: Amygdala; Animals; Avoidance Learning; Discrimination Learning; Extinction, Psychological; Fear; Generalization, Psychological; Hippocampus; Humans; Prefrontal Cortex; Safety
PubMed: 31738952
DOI: 10.1016/j.neubiorev.2019.11.006 -
ELife Jan 2022Debates have arisen as to whether non-human animals actually can learn abstract non-symbolic numerousness or whether they always rely on some continuous physical aspect...
Debates have arisen as to whether non-human animals actually can learn abstract non-symbolic numerousness or whether they always rely on some continuous physical aspect of the stimuli, covarying with number. Here, we investigated archerfish () non-symbolic numerical discrimination with accurate control for covarying continuous physical stimulus attributes. Archerfish were trained to select one of two groups of black dots (Exp. 1: 3 vs 6 elements; Exp. 2: 2 vs 3 elements); these were controlled for several combinations of physical variables (elements' size, overall area, overall perimeter, density, and sparsity), ensuring that only numerical information was available. Generalization tests with novel numerical comparisons (2 vs 3, 5 vs 8, and 6 vs 9 in Exp. 1; 3 vs 4, 3 vs 6 in Exp. 2) revealed choice for the largest or smallest numerical group according to the relative number that was rewarded at training. None of the continuous physical variables, including spatial frequency, were affecting archerfish performance. Results provide evidence that archerfish spontaneously use abstract relative numerical information for both small and large numbers when only numerical cues are available.
Topics: Animals; Cues; Discrimination Learning; Perciformes
PubMed: 35001869
DOI: 10.7554/eLife.74057 -
IScience May 2022With the exception of humans, early cognitive development has been thoroughly investigated only in precocial species, well developed at birth and with a broad behavioral...
With the exception of humans, early cognitive development has been thoroughly investigated only in precocial species, well developed at birth and with a broad behavioral and cognitive repertoire. We investigated another highly altricial species, the zebrafish, , whose embryonic development is very rapid (< 72 h). The hatchlings' nervous system is poorly developed, and their cognitive capacities are largely unknown. Larvae trained at 8 days post fertilization rapidly learned to associate a visual pattern with a food reward, showing significant performance at 10 days post fertilization. We exploited this ability to study hatchlings' discrimination learning capacities. Larvae rapidly and accurately learned color and shape discriminations. They also discriminated a figure from its mirror image and from its 90°-rotated version, although with lower performance. Our study revealed impressive similarities in learning and visual discrimination capacities between newborn and adult zebrafish, despite their enormous differences in brain size and degree of development.
PubMed: 35573200
DOI: 10.1016/j.isci.2022.104283 -
Behavioural Brain Research Jan 2021Accurate discrimination between safe and dangerous stimuli is essential for survival. Prior research has begun to uncover the neural structures that are necessary for...
Accurate discrimination between safe and dangerous stimuli is essential for survival. Prior research has begun to uncover the neural structures that are necessary for learning this discrimination, but exploration of brain regions involved in this learning process has been mostly limited to males. Recent findings show sex differences in discrimination learning, with reduced fear expression to safe cues in females compared to males. Here, we used male and female Sprague Dawley rats to explore neural activation, as measured by Fos expression, in fear and safety learning related brain regions. Neural activation after fear discrimination (Discrimination) was compared between males and females, as well as with fear conditioned (Fear Only) and stimulus presented (Control) conditions. Correlations of discrimination ability and neural activation were also calculated. We uncovered a correlation between central amygdala (CeA) activation and discrimination abilities in males and females. Anterior medial bed nucleus of the stria terminalis (BNST) was the only region where sex differences in Fos counts were observed in the Discrimination condition, and the only region where neural activation significantly differed between Fear Only and Discrimination conditions. Together, these findings indicate the importance of fear expression circuitry in mediating discrimination responses and generate important questions for future investigation.
Topics: Animals; Behavior, Animal; Central Amygdaloid Nucleus; Conditioning, Classical; Discrimination Learning; Fear; Male; Proto-Oncogene Proteins c-fos; Rats; Rats, Sprague-Dawley; Septal Nuclei; Sex Characteristics
PubMed: 32871228
DOI: 10.1016/j.bbr.2020.112884 -
The Journal of the Acoustical Society... Mar 2023Perceptual learning reflects experience-driven improvements in the ability to detect changes in stimulus characteristics. The time course for perceptual learning...
Perceptual learning reflects experience-driven improvements in the ability to detect changes in stimulus characteristics. The time course for perceptual learning overlaps with that for procedural learning (acquiring general skills and strategies) and task learning (learning the perceptual judgment specific to the task), making it difficult to isolate their individual effects. This study was conducted to examine the role of exposure to stimulus, procedure, and task information on learning for auditory temporal-interval discrimination. Eighty-three listeners completed five online sessions that required temporal-interval discrimination (target task). Before the initial session, listeners were differentially exposed to information about the target task's stimulus, procedure, or task characteristics. Learning occurred across sessions, but an exposure effect was not observed. Given the significant learning across sessions and variability within and across listeners, contributions from stimulus, procedure, and task exposure to overall learning cannot be discounted. These findings clarify the influence of experience on temporal perceptual learning and could inform designs of training paradigms that optimize perceptual improvements.
Topics: Acoustic Stimulation; Learning; Auditory Perception; Judgment; Discrimination Learning
PubMed: 37002097
DOI: 10.1121/10.0017548 -
Physiology & Behavior Oct 2021Strain differences in visual abilities and exploratory tendencies can confound rats' performance in cognitive tests of learning and memory. In the present study we...
Strain differences in visual abilities and exploratory tendencies can confound rats' performance in cognitive tests of learning and memory. In the present study we compared the performance of albino Wistar and pigmented Lister Hooded rats in appetitive conditioning and recognition memory procedures, specifically within-subjects inhibitory learning (A+ /AX-) and novel object recognition (NOR) variants. The inhibition task included an excitatory training stage and summation and retardation tests. Difference scores were used to help control for individual variation in baseline nosepoke responding. NOR was tested after a 10 min delay, following 24hr delay and using a recency variant. Discrimination ratios were used to control for individual variation in exploratory activity. In the inhibitory learning procedure, Lister Hooded showed more magazine activity prior to stimulus presentations than Wistar rats but this was a transient effect restricted to day 1 of excitatory training. There was no strain difference in associative learning at the excitatory training stage. The Wistars went on to show some performance advantage at the inhibitory discrimination stage and marginally stronger retardation test performance. In the NOR tasks, there was no significant effect of strain on cognitive performance, but the Wistars showed some advantage in the 10 min delay variant, whereas in the 24hr delay and relative recency NOR variants, the Lister Hooded rats showed some advantage. Overall the results of the present study confirm the suitability of Wistar rats for use in associative learning and basic NOR procedures.
Topics: Animals; Discrimination Learning; Learning; Rats; Rats, Wistar; Recognition, Psychology; Visual Perception
PubMed: 34400194
DOI: 10.1016/j.physbeh.2021.113557 -
PLoS Computational Biology Sep 2022In the natural world, stimulus-outcome associations are often ambiguous, and most associations are highly complex and situation-dependent. Learning to disambiguate these...
In the natural world, stimulus-outcome associations are often ambiguous, and most associations are highly complex and situation-dependent. Learning to disambiguate these complex associations to identify which specific outcomes will occur in which situations is critical for survival. Pavlovian occasion setters are stimuli that determine whether other stimuli will result in a specific outcome. Occasion setting is a well-established phenomenon, but very little investigation has been conducted on how occasion setters are disambiguated when they themselves are ambiguous (i.e., when they do not consistently signal whether another stimulus will be reinforced). In two preregistered studies, we investigated the role of higher-order Pavlovian occasion setting in humans. We developed and tested the first computational model predicting direct associative learning, traditional occasion setting (i.e., 1st-order occasion setting), and 2nd-order occasion setting. This model operationalizes stimulus ambiguity as a mechanism to engage in higher-order Pavlovian learning. Both behavioral and computational modeling results suggest that 2nd-order occasion setting was learned, as evidenced by lack and presence of transfer of occasion setting properties when expected and the superior fit of our 2nd-order occasion setting model compared to the 1st-order occasion setting or direct associations models. These results provide a controlled investigation into highly complex associative learning and may ultimately lead to improvements in the treatment of Pavlovian-based mental health disorders (e.g., anxiety disorders, substance use).
Topics: Association Learning; Conditioning, Classical; Cues; Discrimination Learning; Humans; Learning
PubMed: 36084131
DOI: 10.1371/journal.pcbi.1010410 -
Journal of the Optical Society of... Mar 2021Higher-order spatial correlations contribute strongly to visual structure and salience, and are common in the natural environment. One method for studying this structure...
Higher-order spatial correlations contribute strongly to visual structure and salience, and are common in the natural environment. One method for studying this structure has been through the use of highly controlled texture patterns whose obvious structure is defined entirely by third- and higher-order correlations. Here we examine the effects that longer-term training has on discrimination of 17 such texture types. Training took place in 14 sessions over 42 days. Discrimination performance increased at different rates for different textures. The time required to complete a visit reduced by 25.4% (=0.0004). Factor analysis was applied to data from the learning and experienced phases of the experiment. This indicated that the gain in speed was accompanied by an increase in the number of mechanisms contributing to discrimination. Learning was not affected by sleep quality but was affected by extreme tiredness (<0.01). The improved discrimination and speed were retained for 2.5 months. Overall, the effects were consistent with perceptual learning. The observed learning is likely related to the adaptation of innate mechanisms that underlie our ability to identify nonredundant, visually salient structure in natural images. It may involve cortical V2 and appears to involve increased strength, speed, and breadth of connections within our internal representation of this complex perceptual space.
Topics: Cell Surface Extensions; Machine Learning; Surface Properties
PubMed: 33690477
DOI: 10.1364/JOSAA.413065 -
Neuron Jul 2023Although the hippocampus is crucial for social memory, how social sensory information is combined with contextual information to form episodic social memories remains...
Although the hippocampus is crucial for social memory, how social sensory information is combined with contextual information to form episodic social memories remains unknown. Here, we investigated the mechanisms for social sensory information processing using two-photon calcium imaging from hippocampal CA2 pyramidal neurons (PNs)-which are crucial for social memory-in awake head-fixed mice exposed to social and non-social odors. We found that CA2 PNs represent social odors of individual conspecifics and that these representations are refined during associative social odor-reward learning to enhance the discrimination of rewarded compared with unrewarded odors. Moreover, the structure of the CA2 PN population activity enables CA2 to generalize along categories of rewarded versus unrewarded and social versus non-social odor stimuli. Finally, we found that CA2 is important for learning social but not non-social odor-reward associations. These properties of CA2 odor representations provide a likely substrate for the encoding of episodic social memory.
Topics: Mice; Animals; Odorants; CA2 Region, Hippocampal; Smell; Hippocampus; Learning; Discrimination Learning
PubMed: 37192623
DOI: 10.1016/j.neuron.2023.04.026