Compound Stimulus Research Articles

Navon\u2019s classical paradigm concerning local and global processing relates systematically to visual object classification performance

Forty years ago David Navon tried to tackle a central problem in psychology concerning the time course of perceptual processing: Do we first see the details (local level) followed by the overall outlay (global level) or is it rather the other way around? He did this by developing a now classical paradigm involving the presentation of compound stimuli; large letters composed of smaller letters. Despite the usefulness of this paradigm it remains uncertain whether effects found with compound stimuli relate directly to visual object recognition. It does so because compound stimuli are not actual objects but rather formations of elements and because the elements that form the global shape of compound stimuli are not features of the global shape but rather objects in their own right. To examine the relationship between performance on Navon’s paradigm and visual object processing we derived two indexes from Navon’s paradigm that reflect different aspects of the relationship between global and local processing. We find that individual differences on these indexes can explain a considerable amount of variance in two standard object classification paradigms; object decision and superordinate categorization, suggesting that Navon’s paradigm does relate to visual object processing.

Emparelhamento por identidade e TEA: efeito de pares de estímulos idênticos como consequência de pareamentos corretos

In a replication of a study by Gomes (2011), the effect of the presentation of pairs of identical stimuli after correct matching was assessed in Typical and Multi-sample matching-to-sample tasks. Twenty-four individuals with Autism Spectrum Disorder (ASD) were distributed in two conditions, each with three blocks of trials: Typical, Multi-sample and a mix of both trial types. The order of exposure was counterbalanced across participants within a condition. The first two blocks of trials consisted of both training and testing trials; the third block consisted only of test trials. In Condition 1, the sample stimulus was removed from the screen upon correct matching; in Condition 2 correct matching was followed by presentation of a compound stimulus with two equal elements. Results showed that, regardless of experimental condition and order of exposure to matching-to-sample tasks, percentage of correct responses was higher in Typical Matching test trials. In Condition 2, scores were greater than in Condition 1. For individuals with ASD, control by the relation of identity may be affected by the visual organization of the tasks and by other procedural variables such as the consequences for matching responses, response topography (clicking or dragging) and the training criterion.

Moderate Partially Reduplicated Conditioned Stimuli as Retrieval Cue Can Increase Effect on Preventing Relapse of Fear to Compound Stimuli.

The theory of memory reconsolidation argues that consolidated memory is not unchangeable. Once a memory is reactivated it may go back into an unstable state and need new protein synthesis to be consolidated again, which is called “memory reconsolidation”. Boundary studies have shown that interfering with reconsolidation through pharmacologic or behavioral intervention can lead to the updating of the initial memory, for example, erasing undesired memories. Behavioral procedures based on memory reconsolidation interference have been shown to be an effective way to inhibit fear memory relapse after extinction. However, the effectiveness of retrieval–extinction differs by subtle differences in the protocol of the reactivation session. This represents a challenge with regard to finding an optimal operational model to facilitate its clinical use for patients suffering from pathogenic memories such as those associated with post-traumatic stress disorder. Most of the laboratory models for fear learning have used a single conditioned stimulus (CS) paired with an unconditioned stimulus (US). This has simplified the real situation of traumatic events to an excessive degree, and thus, limits the clinical application of the findings based on these models. Here, we used a basic visual compound CS model as the CS to ascertain whether partial repetition of the compound CSs in conditioning can reactivate memory into reconsolidation. The results showed that the no retrieval group or the 1/3 ratio retrieval group failed to open the memory reconsolidation time window. The 2/3 repetition retrieval group and the whole repetition retrieval group were able to prevent fear reinstatement, whereas only a 2/3 ratio repetition of the initial compound CS as a reminder could inhibit spontaneous recovery. We inferred that a retrieval–extinction paradigm was also effective in a more complex model of fear if a sufficient prediction error (PE) could be generated in the reactivation period. In addition, in order to achieve an optimal effect, a CS of moderate discrepancy should be used as a reminder.

The Emergence of Stimulus Relations: Human and Computer Learning.

Traditionally, investigations in the area of stimulus equivalence have employed humans as experimental participants. Recently, however, artificial neural network models (often referred to as connectionist models [CMs]) have been developed to simulate performances seen among human participants when training various types of stimulus relations. Two types of neural network models have shown particular promise in recent years. RELNET has demonstrated its capacity to approximate human acquisition of stimulus relations using simulated matching-to-sample (MTS) procedures (e.g., Lyddy & Barnes-Holmes Journal of Speech and Language Pathology and Applied Behavior Analysis, 2, 14-24, 2007). Other newly developed connectionist algorithms train stimulus relations by way of compound stimuli (e.g., Tovar & Chavez The Psychological Record, 62, 747-762, 2012; Vernucio & Debert The Psychological Record, 66, 439-449, 2016). What makes all of these CMs interesting to many behavioral researchers is their apparent ability to simulate the acquisition of diversified stimulus relations as an analogue to human learning; that is, neural networks learn over a series of training epochs such that these models become capable of deriving novel or untrained stimulus relations. With the goal of explaining these quickly evolving approaches to practical and experimental endeavors in behavior analysis, we offer an overview of existing CMs as they apply to behavior-analytic theory and practice. We provide a brief overview of derived stimulus relations as applied to human academic remediation, and we argue that human and simulated human investigations have symbiotic experimental potential. Additionally, we provide a working example of a neural network referred to as emergent virtual analytics (EVA). This model demonstrates a process by which artificial neural networks can be employed by behavior-analytic researchers to understand, simulate, and predict derived stimulus relations made by human participants.

Using intraverbal prompts to increase divergent intraverbal responses by a child with autism

We examined the effectiveness of intraverbal prompts to increase the number of divergent responses to categorical questions composed of compound stimuli (e.g., Name some red things) for a 6‐year‐old child with autism. The intraverbal prompts involved providing the function, feature, and class of the target responses. A multiple probe across behaviors design was used. Results indicated that the child's total number of divergent responses was increased and maintained during 2‐week follow‐up probe trials. Novel responses were observed across conditions.

Different Neural Correlates of Emotion-Label Words and Emotion-Laden Words: An ERP Study.

It is well-documented that both emotion-label words (e.g., sadness, happiness) and emotion-laden words (e.g., death, wedding) can induce emotion activation. However, the neural correlates of emotion-label words and emotion-laden words recognition have not been examined. The present study aimed to compare the underlying neural responses when processing the two kinds of words by employing event-related potential (ERP) measurements. Fifteen Chinese native speakers were asked to perform a lexical decision task in which they should judge whether a two-character compound stimulus was a real word or not. Results showed that (1) emotion-label words and emotion-laden words elicited similar P100 at the posteriors sites, (2) larger N170 was found for emotion-label words than for emotion-laden words at the occipital sites on the right hemisphere, and (3) negative emotion-label words elicited larger Late Positivity Complex (LPC) on the right hemisphere than on the left hemisphere while such effect was not found for emotion-laden words and positive emotion-label words. The results indicate that emotion-label words and emotion-laden words elicit different cortical responses at both early (N170) and late (LPC) stages. In addition, right hemisphere advantage for emotion-label words over emotion-laden words can be observed in certain time windows (i.e., N170 and LPC) while fails to be detected in some other time window (i.e., P100). The implications of the current findings for future emotion research were discussed.

P 94 Integration of audio-visual information in the subthalamic nucleus – evidence from local field potential recordings

As part of the basal ganglia the subthalamic nucleus is functionally integrated into motoric, limbic, and associative loops connecting the basal ganglia and the prefrontal cortex. Recent recordings from local field potentials have shown, that the human STN is also involved in processing of automatic change detection: sensory changes in a subject’s auditory environment result in altered event related local field potentials. Electrophysiological recordings from the STN in rats indicate, that the functional meaning of the STN’s responsiveness to sensory inputs could be the integration of sensory and motor information. In the present study we investigated 11 patients suffering from Parkinson’s Disease. While performing a task event related local field potentials were recorded from the STN. The task comprised the presentation of standard and rarely occurring deviant stimuli. Stimuli were either monomodal (auditory or visual) or multimodal stimuli (compound stimuli consisting of the stimuli from the monomodal conditions). Patients had to response to the deviant stimuli in one of the sensory domains. The analysis of the event related field potentials indicated a preferred processing of auditory in comparison to visual stimuli in an early time window (100–300 ms). Moreover, in the multimodal condition the presentation of auditory deviants while patients had to respond to a visual deviant had a modulatory effect on the local field potentials’ amplitude. These findings suggest that the STN receives and integrates information from different modality most likely in order to use this information in the initiation or withholding of actions.

Tonic noradrenergic activity modulates explorative behavior and attentional set shifting: Evidence from pupillometry and gaze pattern analysis.

A constant task for every living organism is to decide whether to exploit rewards associated with current behavior or to explore the environment for more rewarding options. Current empirical evidence indicates that exploitation is related to phasic whereas exploration is related to tonic firing mode of noradrenergic neurons in the locus coeruleus. In humans, this exploration-exploitation trade-off is subserved by the ability to flexibly switch attention between task-related and task-irrelevant information. Here, we investigated whether this function, called attentional set shifting, is related to exploration and tonic noradrenergic discharge. We measured pretrial baseline pupil dilation, proved to be strongly correlated with the activity of the locus coeruleus, while human participants took part in well-known tasks of attentional set shifting. Study 1 used the Wisconsin Card Sorting Task, whereas in Study 2, the Intra/Extradimensional Set Shifting Task was used. Both tasks require participants to choose between different compound stimuli based on feedback provided for their previous decisions. During the task, stimulus-reward contingencies change periodically, thus participants are repeatedly required to reassess which stimulus features are relevant (i.e., they shift their attentional set). Our results showed that baseline pupil diameter steadily decreased when the stimulus-reward contingencies were stable, whereas they suddenly increased when these contingencies changed. Analysis of looking patterns also confirmed the presence of exploratory behavior during attentional set shifting. Thus, our results suggest that tonic firing mode of noradrenergic neurons in the locus coeruleus is implicated in attentional set shifting, as it regulates the amount of exploration.

Reward and punishment-based compound cue learning and generalization in opiate dependency.

Substance dependence is thought to be mediated by abnormalities in cognitive abilities, but how this impacts decision-making remains unclear. This study aimed to test whether people who are opiate dependent differed from never-dependent controls in learning from reward and punishment or in the generalization of learning to novel conditions. Participants with opiate dependency consisted of 21 people who were outpatients in a methadone maintenance program; the control group consisted of 21 healthy participants with no histories of substance abuse. Subjects completed a computer-based task that involved two phases: the training phase involved participants being presented with compound stimulus (a shape and color) in each trial, with the goal of learning which compounds to 'pick' for rewards or 'skip' to avoid punishment. The test phase involved a transfer test, where stimuli from the first phase were combined together to form novel compounds without feedback. The control group demonstrated fewer errors compared to opiate-dependent individuals during the training phase. In the test phase, controls used prior knowledge of both shapes and colors in responding; however, opiate-dependent individuals used shapes but did not use their knowledge of color to modulate responding. When performance during training was equated in the groups using a learning threshold, this difference between groups on the generalization test remained. A deficit in learning generalization might be indicative of group differences in learning strategies in operation during training; however, future work is necessary to uncover the specific neural substrates in action during transfer tasks, and to determine the effects of acute methadone dosage on decision-making.

Components of competitor priming in task switching.

Executing an action in response to a stimulus is thought to result in the creation of an event code that integrates stimulus and action features (Allport, 1987; Hommel in Visual Cognition 5: 183-216, 1998). When switching between tasks, competitor priming occurs if a distractor stimulus cues the retrieval of a previously established event code in which that distractor is bound to a competing task, creating a source of interference with the current task whereby the observer is encouraged to apply the competing task to the distractor. We propose a second aspect of competitor priming: the misapplication of the retrieved competing task to the target stimulus. We report two task-switching experiments in which tasks applied to picture-word compound stimuli were manipulated to create conditions in which this second aspect of competitor priming could be revealed and distinguished from other sources of task- and stimulus-based priming. A substantial increase in competitor priming was observed when subjects switched between tasks that required very different processing operations and the competing task was highly relevant to the target stimulus. These results are consistent with our claim that competitor priming can result from applying the competing task either to the distractor that cued it or to the target stimulus.

Measuring nonlinear signal combination using EEG.

Relatively little is known about the processes, both linear and nonlinear, by which signals are combined beyond V1. By presenting two stimulus components simultaneously, flickering at different temporal frequencies (frequency tagging) while measuring steady-state visual evoked potentials, we can assess responses to the individual components, including direct measurements of suppression on each other, and various nonlinear responses to their combination found at intermodulation frequencies. The result is a rather rich dataset of frequencies at which responses can be found. We presented pairs of sinusoidal gratings at different temporal frequencies, forming plaid patterns that were "coherent" (looking like a checkerboard) and "noncoherent" (looking like a pair of transparently overlaid gratings), and found clear intermodulation responses to compound stimuli, indicating nonlinear summation. This might have been attributed to cross-orientation suppression except that the pattern of intermodulation responses differed for coherent and noncoherent patterns, whereas the effects of suppression (measured at the component frequencies) did not. A two-stage model of nonlinear summation involving conjunction detection with a logical AND gate described the data well, capturing the difference between coherent and noncoherent plaids over a wide array of possible response frequencies. Multistimulus frequency-tagged EEG in combination with computational modeling may be a very valuable tool in studying the conjunction of these signals. In the current study the results suggest a second-order mechanism responding selectively to coherent plaid patterns.

Assessing preference for and reinforcing efficacy of components of social interaction in individuals with autism spectrum disorder

We evaluated the degree to which social interactions are reinforcing for two individuals with autism spectrum disorder by comparing individual components (i.e., edible, vocal, and physical interaction) alone and in combination. First, we conducted preference assessments to determine preference hierarchies within three stimulus classes: edible, vocal, and physical interaction. Second, we evaluated preference for individual stimuli across these classes. Third, we examined the relative reinforcing efficacy of highly preferred stimuli assessed individually. Fourth, with individuals for whom physical and vocal stimuli served as reinforcers, we evaluated if adding the other component, physical or vocal, increased the effectiveness of that consequence as a reinforcer. Results suggested differences in the relative reinforcing efficacy of components of social interaction. Additionally, combining components to form compound stimuli produced idiosyncratic differences in relative rates of responding.

Effects of serotonergic hallucinogen R(−)‐2,5‐Dimethoxy‐4‐iodoamphetamine (DOI) on temporal discrimination in mice

R(−)‐2,5‐Dimethoxy‐4‐iodoamphetamine (DOI) and other compounds with agonist affinity for serotonergic 5‐HT2A receptors are hallucinogenic drugs of abuse, but also have therapeutic potential in numerous neuropsychiatric conditions, including major depressive disorder, post‐traumatic stress disorder, and in the treatment of migraine and cluster headaches. Thus, commonly abused hallucinogens could serve as lead compounds in the development of new therapeutic drugs. While there are already behavioral assays useful in the study of these compounds, it remains difficult to measure the primary effects of hallucinogenic drugs, which are subjective and unobservable. The drug‐elicited head twitch response (HTR) is a technically‐simple observational assay which yields dose‐dependent data, is sensitive to 5‐HT2A antagonism, and has a strong predictive validity for hallucinogenic effects in humans. However, it is not clear which aspect of the cluster of hallucinogenic effects is modeled by the HTR. Because hallucinogens and other psychoactive drugs have been shown to disrupt temporal discrimination in rodents and in humans, a model incorporating time perception may have better face validity than the HTR. In these studies, we used a temporal discrimination assay to measure the effects of DOI in male Swiss‐Webster mice in order to validate the procedure by determining whether reliable drug effects would be achievable in mice, would be dose‐dependent, and would be reversible by 5‐HT2A antagonism. In this procedure, a light‐tone compound stimulus was presented for either a short (2.7 sec) or long (27 sec) duration. Responses in one nose‐poke aperture were reinforced after passage of a short stimulus presentation, while responses in the other nose‐poke aperture were reinforced after passage of long stimulus presentation. Mice required a relatively large number of sessions (>60) to reach criterion performance, but once trained, administration of DOI dose‐dependently disrupted temporal discrimination. The doses of DOI required to alter temporal discrimination were relatively high, and are on the descending limb of dose‐effect functions derived in HTR studies. Nevertheless, these effects were at least partially mediated by 5‐HT2A agonism, as the selective 5‐HT2A antagonist M100907 dose‐dependently reversed the effects of DOI on temporal discrimination. Despite the large time investment required to train murine subjects, temporal discrimination appears to be a useful behavioral pharmacology assay to specifically study the effects of novel hallucinogen‐like drugs on time perception, and may be a valuable in the preclinical development of new therapeutic drugs with serotonergic mechanisms.Support or Funding InformationThese studies were funded in part by an NIGMS IDeA Program award (GM110702) and by the UAMS Translational Research Institute (RR029884), and MPT received a Summer Undergraduate Research Fellowships from the American Society of Pharmacology and Experimental Therapeutics to work on these studies.

Cue-induced food seeking after punishment is associated with increased Fos expression in the lateral hypothalamus and basolateral and medial amygdala.

In humans, relapse to unhealthy eating habits following dieting is a significant impediment to obesity treatment. Food-associated cues are one of the main triggers of relapse to unhealthy eating during self-imposed abstinence. Here we report a behavioral method examining cue-induced relapse to food seeking following punishment-induced suppression of food taking. We trained male rats to lever press for food pellets that were delivered after a 10-s conditional stimulus (CS) (appetitive). Following training, 25% of reinforced lever presses resulted in the presentation of a compound stimulus consisting of a novel CS (aversive) and the appetitive CS followed by a pellet and footshock. After punishment-imposed abstinence, we tested the rats in an extinction test where lever pressing resulted in the presentation of either the appetitive or aversive CS. We then compared activity of lateral hypothalamus (LH) and associated extrahypothalamic regions following this test. We also assessed Fos expression in LH orexin and GABA neurons. We found that cue-induced relapse of food seeking on test was higher in rats tested with the appetitive CS compared to the aversive CS. Relapse induced by the appetitive CS was associated with increased Fos expression in LH, caudal basolateral amygdala (BLA), and medial amygdala (MeA). This relapse was also associated with increased Fos expression in LH orexin and VGAT-expressing neurons. These data show that relapse to food seeking can be induced by food-associated cues after punishment-imposed abstinence, and this relapse is associated with increased activity in LH, caudal BLA, and MeA. (PsycINFO Database Record

Steps to Health in Cognitive Aging: Effects of Physical Activity on Spatial Attention and Executive Control in the Elderly.

The purpose of this study was to investigate whether physical activity (PA) habits may positively impact performance of the orienting and executive control networks in community-dwelling aging individuals and diabetics, who are at risk of cognitive dysfunction. To this aim, we tested cross-sectionally whether age, ranging from late middle-age to old adulthood, and PA level independently or interactively predict different facets of the attentional performance. Hundred and thirty female and male individuals and 22 adults with type 2 diabetes aged 55–84 years were recruited and their daily PA (steps) was objectively measured by means of armband monitors. Participants performed a multifunctional attentional go/no-go reaction time (RT) task in which spatial attention was cued by means of informative direct cues of different sizes followed by compound stimuli with local and global target features. The performance efficiency of the orienting networks was estimated by computing RT differences between validly and invalidly cued trials, that of the executive control networks by computing local switch costs that are RT differences between switch and non-switch trials in mixed blocks of global and local target trials. In regression analyses performed on the data of non-diabetic elderlies, overall RTs and orienting effects resulted jointly predicted by age and steps. Age predicted overall RTs in low-active individuals, but orienting effects and response errors in high-active individuals. Switch costs were predicted by age only, with larger costs at older age. In the analysis conducted with the 22 diabetics and 22 matched non-diabetic elderlies, diabetic status and daily steps predicted longer and shorter RTs, respectively. Results suggest that high PA levels exert beneficial, but differentiated effects on processing speed and attentional networks performance in aging individuals that partially counteract the detrimental effects of advancing age and diabetic status. In conclusion, adequate levels of overall PA may positively impinge on brain efficiency and attentional control and should be therefore promoted by actions that support lifelong PA participation and impact the built environment to render it more conducive to PA.

Post-traumatic stress disorder symptom burden and gender each affect generalization in a reward- and punishment-learning task.

Post-traumatic stress disorder (PTSD) can develop following exposure to a traumatic event. Re-experiencing, which includes intrusive memories or flashbacks of the trauma, is a core symptom cluster of PTSD. From an associative learning perspective, this cluster may be attributed to cues associated with the trauma, which have come to elicit symptoms in a variety of situations encountered in daily life due to a tendency to overgeneralize. Consistent with this, prior studies have indicated that both individuals with clinically diagnosed with PTSD, and those with self-reported symptoms who may not meet full diagnostic criteria, show changes in generalization. Building on prior research, the current study examined whether PTSD symptom burden, but also gender, veteran status, and combat experience–all associated with PTSD vulnerability–modulate learning and generalization in a computer-based task. Participants were presented with stimulus compounds consisting of a foreground and background that could be predictive of reward, punishment or no outcome. Learning was followed by a generalization test where these components were recombined to form novel configurations. An interaction between PTSD symptom burden and gender was found where females with more severe PTSD symptoms showed no evidence of sensitivity to the background. This result is consistent with increased generalization, and may indicate a decrease in the ability to process cue configurations leading to re-experiencing in a variety of situations. Further work is indicated to help elucidate the cognitive processes driving gender differences that may confer vulnerability to PTSD.

Compound Stimulus Presentation Does Not Deepen Extinction in Human Causal Learning.

Models of associative learning have proposed that cue-outcome learning critically depends on the degree of prediction error encountered during training. Two experiments examined the role of error-driven extinction learning in a human causal learning task. Target cues underwent extinction in the presence of additional cues, which differed in the degree to which they predicted the outcome, thereby manipulating outcome expectancy and, in the absence of any change in reinforcement, prediction error. These prediction error manipulations have each been shown to modulate extinction learning in aversive conditioning studies. While both manipulations resulted in increased prediction error during training, neither enhanced extinction in the present human learning task (one manipulation resulted in less extinction at test). The results are discussed with reference to the types of associations that are regulated by prediction error, the types of error terms involved in their regulation, and how these interact with parameters involved in training.

The timescale of adaptation at early and mid-level stages of visual processing.

The visual environment changes at multiple timescales. It has been recently demonstrated that visual adaptation is composed of multiple mechanisms operating at differing timescales to accommodate the environmental changes. However, whether multiple adaptation mechanisms correspond to different stages of visual processing remains unclear. To address this issue, in the current study, we compared the timescales of adaptation between the stages of early and mid-level visual processing by tracking the decay of the curvature aftereffect after adaptation to either a compound stimulus or a component stimulus. The results revealed a slower decay for the compound adaptation condition than for the component adaptation condition. Our finding indicates that neural mechanisms for visual adaptation are more sluggish at the mid level than those at the early stage of visual processing.

The effect of compound stimulus to conditioned fear extinction in retrieval-extinction paradigm

The effect of compound stimulus to conditioned fear extinction in retrieval-extinction paradigm

Cross-Species Translational Findings in the Discriminative Stimulus Effects of Ethanol.

The progress on understanding the pharmacological basis of ethanol's discriminative stimulus effects has been substantial, but appears to have plateaued in the past decade. Further, the cross-species translational efforts are clear in laboratory animals, but have been minimal in human subject studies. Research findings clearly demonstrate that ethanol produces a compound stimulus with primary activity through GABA and glutamate receptor systems, particularly ionotropic receptors, with additional contribution from serotonergic mechanisms. Further progress should capitalize on chemogenetic and optogenetic techniques in laboratory animals to identify the neural circuitry involved in mediating the discriminative stimulus effects of ethanol. These infrahuman studies can be guided by in vivo imaging of human brain circuitry mediating ethanol's subjective effects. Ultimately, identifying receptors systems, as well as where they are located within brain circuitry, will transform the use of drug discrimination procedures to help identify possible treatment or prevention strategies for alcohol use disorder.