Generalization gradients for fear and disgust in human associative learning

Previous research indicates that excessive fear is a critical feature in anxiety disorders; however, recent studies suggest that disgust may also contribute to the etiology and maintenance of some anxiety disorders. It remains unclear if differences exist between these two threat-related emotions in conditioning and generalization. Evaluating different patterns of fear and disgust learning would facilitate a deeper understanding of how anxiety disorders develop. In this study, 32 college students completed threat conditioning tasks, including conditioned stimuli paired with frightening or disgusting images. Fear and disgust were divided into two randomly ordered blocks to examine differences by recording subjective US expectancy ratings and eye movements in the conditioning and generalization process. During conditioning, differing US expectancy ratings (fear vs. disgust) were found only on CS-, which may demonstrated that fear is associated with inferior discrimination learning. During the generalization test, participants exhibited greater US expectancy ratings to fear-related GS1 (generalized stimulus) and GS2 relative to disgust GS1 and GS2. Fear led to longer reaction times than disgust in both phases, and the pupil size and fixation duration for fear stimuli were larger than for disgust stimuli, suggesting that disgust generalization has a steeper gradient than fear generalization. These findings provide preliminary evidence for differences between fear- and disgust-related stimuli in conditioning and generalization, and suggest insights into treatment for anxiety and other fear- or disgust-related disorders.

“Now I get it !”: Eureka experiences during the acquisition of mathematical concepts

Many famous scientists have reported anecdotes where a new understanding occurred to them suddenly, in an unexpected flash. Do people generally experience such “Eureka” moments when learning science concepts, and how do these episodes relate to learning mechanisms? To address these questions, we developed a new paradigm where participants learned a mathematical concept in the lab, in a single experimental session. Participants were given 1 to 7 lessons introducing the concept of geodesic, which generalizes the common notion of straight line to straight trajectories drawn on curved surfaces. They were then tested on their understanding of geodesics in several tasks requiring increasing levels of generalization from the information taught in the lessons. Our findings indicate that insight experiences are common when learning mathematics, as such experiences were reported by about 61% of our participants. Moreover, the participants who experienced insights performed better in a generalization test where they needed to identify a type of geodesic that had not been presented in the lessons, and this, even after controlling for their confidence in their own understanding. Based on these findings, we suggest that concept learning involves mechanisms that generally are not accessible to introspection, except when the process reaches key computational steps and insights are triggered.

“Now I get it !”: Eureka experiences during the acquisition of mathematical concepts

Many famous scientists have reported anecdotes where a new understanding occurred to them suddenly, in an unexpected flash. Do people generally experience such “Eureka” moments when learning science concepts, and how do these episodes relate to learning mechanisms? To address these questions, we developed a new paradigm where participants learned a mathematical concept in the lab, in a single experimental session. Participants were given 1 to 7 lessons introducing the concept of geodesic, which generalizes the common notion of straight line to straight trajectories drawn on curved surfaces. They were then tested on their understanding of geodesics in several tasks requiring increasing levels of generalization from the information taught in the lessons. Our findings indicate that insight experiences are common when learning mathematics, as such experiences were reported by about 61% of our participants. Moreover, the participants who experienced insights performed better in a generalization test where they needed to identify a type of geodesic that had not been presented in the lessons, and this, even after controlling for their confidence in their own understanding. Based on these findings, we suggest that concept learning involves mechanisms that generally are not accessible to introspection, except when the process reaches key computational steps and insights are triggered.

Two distinct networks containing position-tolerant representations of actions in the human brain

Humans can recognize others actions in the social environment. This recognition ability is tolerant to drastic variations in the visual input caused by the movements of people in the environment. What neural underpinnings support this position-tolerant action recognition? In the present study, we aimed to identify regions in the brain that contain position-tolerant representations of actions and explore the representational content of these regions. We recorded fMRI data from twenty-two subjects while they observed video clips of ten different human actions in Point Light Display format. Each stimulus was presented in either the upper or the lower visual fields. We used multivoxel pattern analysis and a searchlight technique to identify brain regions that contain position-tolerant action representation. In a generalization test, linear support vector machine classifiers were trained with fMRI patterns in response to stimuli presented in one position and tested with stimuli presented in another position. Results showed above-chance classification in the left and right lateral occipitotemporal cortex, right inferior intraparietal sulcus, and right superior intraparietal sulcus. To investigate the representational content of these regions, we constructed models based on the objective measures of movements and human subjective judgments about actions. We then evaluated the brain similarity matrix from the cross-position classification analysis based on these models. Results showed cross-position classifications in the lateral occipito-temoiral ROIs was more strongly related to the subjective judgements while those in the dorsal parietal ROIs were more strongly related to the objective movements. An ROI representational similarity analysis futher revealed separation of dorsal and lateral regions. These results suggest the existence of two networks that contain abstract representations of human actions with distinct representational content.

Stimulus Control of Odorant Concentration: Pilot Study of Generalization and Discrimination of Odor Concentration in Canines

Despite dogs’ widespread use as detection systems, little is known about how dogs generalize to variations of an odorant’s concentration. Further, it is unclear whether dogs can be trained to discriminate between similar concentration variations of an odorant. Four dogs were trained to an odorant (0.01 air dilution of isoamyl acetate) in an air-dilution olfactometer, and we assessed spontaneous generalization to a range of concentrations lower than the training stimulus (Generalization Test 1). Dogs generalized to odors within a 10-fold range of the training odorant. Next, we conducted discrimination training to suppress responses to concentrations lower than a concentration dogs showed initial responding towards in Generalization Test 1 (0.0025 air dilution). Dogs successfully discriminated between 0.0025 and 0.01, exceeding 90% accuracy. However, when a second generalization test was conducted (Generalization Test 2), responding at the 0.0025 concentration immediately recovered and was no different than in Generalization Test 1. Dogs were then tested in another generalization test (Compound Discrimination and Generalization) in which generalization probes were embedded within discrimination trials, and dogs showed suppression of responding to the 0.0025 concentration and lower concentrations in this preparation. These data suggest dogs show limited spontaneous generalization across odor concentration and that dogs can be trained to discriminate between similar concentrations of the same odorant. Stimulus control, however, may depend on the negative stimulus, suggesting olfactory concentration generalization may depend on relative stimulus control. These results highlight the importance of considering odor concentration as a dimension for generalization in canine olfactory research.

Comparing perceptual category learning across modalities in the same individuals

Category learning is a fundamental process in human cognition that spans the senses. However, much still remains unknown about the mechanisms supporting learning in different modalities. In the current study, we directly compared auditory and visual category learning in the same individuals. Thirty participants (22 F; 18-32 years old) completed two unidimensional rule-based category learning tasks in a single day—one with auditory stimuli and another with visual stimuli. We replicated the results in a second experiment with a larger online sample (N = 99, 45 F, 18-35 years old). The categories were identically structured in the two modalities to facilitate comparison. We compared categorization accuracy, decision processes as assessed through drift-diffusion models, and the generalizability of resulting category representation through a generalization test. We found that individuals learned auditory and visual categories to similar extents and that accuracies were highly correlated across the two tasks. Participants had similar evidence accumulation rates in later learning, but early on had slower rates for visual than auditory learning. Participants also demonstrated differences in the decision thresholds across modalities. Participants had more categorical generalizable representations for visual than auditory categories. These results suggest that some modality-general cognitive processes support category learning but also suggest that the modality of the stimuli may also affect category learning behavior and outcomes.

Trait anxiety is associated with reduced typicality asymmetry in fear generalization

In fear conditioning, training with typical category exemplars has been shown to promote fear generalization to novel exemplars of the same category, whereas training with atypical category exemplars supports limited if any generalization to other category members, amounting to a typicality asymmetry in fear generalization. The present study sought to examine how trait anxiety bears on typicality asymmetry in fear generalization. Participants in one condition were presented with typical exemplars during fear acquisition and atypical exemplars of the same category in the subsequent generalization test (typical condition), whereas in the other group, atypical and typical exemplars were presented during fear acquisition and generalization test, respectively (atypical condition). We observed a typicality asymmetry in fear generalization in self-reported expectancy ratings in low trait anxious individuals only. High trait anxious individuals showed a similar degree of fear generalization in both conditions. The current results help illuminate why some individuals are at risk for exhibiting broad fear generalization after exposure to an aversive event.

The serotonin transporter modulates decisional anhedonia

Serotonin transporter gene variance has long been considered an important factor contributing to depression. However, meta-analyses yielded inconsistent findings recently, asking for further understanding of the link between the gene and depression-related symptoms. One key feature of depression is anhedonia. Anhedonia is not one united feature but involves consummatory, anticipatory, and decisional aspects. These different aspects of anhedonia can be particularly well investigated in rodents. While data exist on the effect of serotonin transporter gene knockout in rodents on consummatory and anticipatory anhedonia, with mixed outcomes, the effect on decisional anhedonia has not been investigated thus far in rats. Here, we tested whether serotonin transporter knockout (5-HTT-/-) contributes to decisional anhedonia. To this end, we established a novel touchscreen-based task employing a ‘go/go’ task for decision-making under ambiguity. Both genotypes of rats were able to reach 70% accuracy across three consecutive sessions. However, 5-HTT+/+ rats performed more optimal decision-making compared to 5-HTT-/- rats during the course of discriminative conditioning for the conditioned stimulus associated with high reward value at the beginning. 5-HTT+/+ rats gradually increased response time to generalization stimuli across the three generalization test sessions, while 5-HTT-/- rats tended to decrease response time. The monotonic graded responses towards the stimuli did not alter for both genotypes. The results suggest that the association between the serotonin transporter gene and anhedonia may dynamically change over time when processing ambiguous information. This may explain the inconsistent findings on the association between the serotonin transporter gene and various aspects of depression in humans.

Social aversive generalization learning sharpens the tuning of visuocortical neurons to facial identity cues

Defensive system activation promotes heightened perception of threat signals, and excessive attention to threat signals has been discussed as a contributory factor in the etiology of anxiety disorders. However, a mechanistic account of attentional modulation during fear-relevant processes, especially during fear generalization remains elusive. To test the hypothesis that social fear generalization prompts sharpened tuning in the visuocortical representation of social threat cues, 67 healthy participants underwent differential fear conditioning, followed by a generalization test in which participants viewed faces varying in similarity with the threat-associated face. We found that generalization of social threat sharpens visuocortical tuning of social threat cues, whereas ratings of fearfulness showed generalization, linearly decreasing with decreasing similarity to the threat-associated face. Moreover, individuals who reported greater anxiety in social situations also showed heightened sharpened tuning of visuocortical neurons to facial identity cues, indicating the behavioral relevance of visuocortical tuning during generalization learning.

Sistema de Classificação de Assento Adaptado (CAA) baseado na Classificação Internacional de Funcionalidade (CIF) | Adapted Seat Classification System (CAS) based on the International Classification of Functionality (ICF

A fidedigna transmissão de informações sobre equipamentos de tecnologia assistiva (TA) e de condições da saúde é essencial para o melhoramento de qualidade de vida das pessoas. Por isso a OMS criou a Classificação Internacional de Funcionalidade (CIF), que trata da classificação de funcionalidade de pacientes. No entanto ela possui uma lacuna no que diz respeito à classificação de TA. Dessa maneira propôs-se nesse trabalho o desenvolvimento de um sistema de Classificação de Assento Adaptado (CAA) que possa ser utilizado juntamente com a CIF. Para isso estudou-se a CIF e os assentos adaptados (AAs) disponibilizados pelo SUS para definir os elementos a serem codificados e de que maneira seria desenvolvido a CAA. Após sua criação ele foi posto à prova com um teste de aplicação e de generalização mostrando-se capaz de classificar todos os componentes de AA do SUS, além de se apresentar de maneira concisa e confiável para a transmissão de informações referentes à AAs.*****The reliable transmission of information on Assistive Technology (AT) equipment and health conditions is essential for improving people's quality of life. That is why WHO created the International Classification of Functionality (ICF), which deals with the classification of patients' functionality. However, it has a gap with respect to AT classification. So, we proposed the development of an Adapted Seat Classification System (CAS) that could be used together with ICF. For this, ICF and the adapted seats made available by SUS were studied to define the elements to be coded and how the CAS would be developed. After its creation, it was submitted to an application and generalization test demonstrating the capability of classifying all the components of adapted seats of SUS, besides presenting a concise and reliable way for the transmission of information referring to adapted seats.