Stimulus Selection Research Articles

Revealing hidden sensorimotor memories in mice with AD‐relevant pathology

AbstractBackgroundMemories must be accessible for them to be useful. Alzheimer’s disease (AD) is a progressive form of dementia in which cognitive capacities slowly deteriorate due to underlying neurodegeneration. Interestingly, anecdotal observations have demonstrated that Alzheimer’s patients can exhibit cognitive fluctuations during all stages of the disease. In particular, it is thought that contextual factors are critical for unlocking these hidden memories. To date, however, exploration of the neural basis of cognitive fluctuations has been hampered due to the lack of a behavioral approach in mouse models to dissociate memories from contextual performance.MethodOur previous work demonstrated that interleaving ‘reinforced’ trials with trials without reinforcement (‘probe’ trials) in an auditory go/no‐go discrimination task, allows us to distinguish between acquired sensorimotor memories and their contextual expression. Here, we used this approach, together with two‐photon calcium imaging on behaving AD‐relevant mice (APP/PS1+), to determine whether amyloid accumulation impacts underlying sensorimotor memories (measured using ‘probe’ trials) and/or contextual‐performance (measured using ‘reinforced’ trials) in an age dependent manner.ResultImportantly, peripheral auditory function, measured using the threshold for detecting an auditory brainstem response, was similar between WT and APP/PS1+ mice. We found that while contextual‐performance is significantly impaired in young adult APP/PS1+ mice compared to age‐matched controls, these animals show only minor impairments in the underlying sensorimotor memories. However, middle aged APP/PS1+ mice show deficits in both domains. The impairment found in the young adults was accompanied by a reduction in stimulus selectivity and behavioral encoding in the auditory cortex of APP/PS1+ mice that that can be partially restored in probe trials. Ongoing analyses aim to identify whether this impairment is cortex‐wide or is concentrated near Aβ plaques. Finally, these effects were recapitulated by using a reinforcement learning model that accounts for changes in contextual signals. The main network model parameters affected between the control and the APP/PS1+ mice were those governing contextual scaling and behavioral inhibition.ConclusionThese results suggest that Aβ deposition impacts circuits involved in contextual computations before those involved in acquiring knowledge and that neural circuit interventions, such as modulating inhibition, may hold promise to reveal hidden memories.

Dissociative Effects of Age on Neural Differentiation at the Category and Item Levels.

Increasing age is associated with age-related neural dedifferentiation, a reduction in the selectivity of neural representations, which has been proposed to contribute to cognitive decline in older age. Recent findings indicate that when operationalized in terms of selectivity for different perceptual categories, age-related neural dedifferentiation and the apparent age-invariant association of neural selectivity with cognitive performance are largely restricted to the cortical regions typically recruited during scene processing. It is currently unknown whether this category-level dissociation extends to metrics of neural selectivity defined at the level of individual stimulus items. Here, we examined neural selectivity at the category and item levels using multivoxel pattern similarity analysis (PSA) of fMRI data. Healthy young and older male and female adults viewed images of objects and scenes. Some items were presented singly, while others were either repeated or followed by a "similar lure." In agreement with recent findings, category-level PSA revealed robustly lower differentiation in older than in younger adults in scene-selective, but not object-selective, cortical regions. By contrast, at the item level, robust age-related declines in neural differentiation were evident for both stimulus categories. Additionally, we identified an age-invariant association between category-level scene selectivity in the parahippocampal place area and subsequent memory performance, but no such association was evident for item-level metrics. Lastly, category- and item-level neural metrics were uncorrelated. Thus, the present findings suggest that age-related category- and item-level dedifferentiation depend on distinct neural mechanisms.

Repeated passive visual experience modulates spontaneous and non-familiar stimuli-evoked neural activity

Familiarity creates subjective memory of repeated innocuous experiences, reduces neural and behavioral responsiveness to those experiences, and enhances novelty detection. The neural correlates of the internal model of familiarity and the cellular mechanisms of enhanced novelty detection following multi-day repeated passive experience remain elusive. Using the mouse visual cortex as a model system, we test how the repeated passive experience of a 45° orientation-grating stimulus for multiple days alters spontaneous and non-familiar stimuli evoked neural activity in neurons tuned to familiar or non-familiar stimuli. We found that familiarity elicits stimulus competition such that stimulus selectivity reduces in neurons tuned to the familiar 45° stimulus; it increases in those tuned to the 90° stimulus but does not affect neurons tuned to the orthogonal 135° stimulus. Furthermore, neurons tuned to orientations 45° apart from the familiar stimulus dominate local functional connectivity. Interestingly, responsiveness to natural images, which consists of familiar and non-familiar orientations, increases subtly in neurons that exhibit stimulus competition. We also show the similarity between familiar grating stimulus-evoked and spontaneous activity increases, indicative of an internal model of altered experience.

The "Seven Deadly Sins" of Neophobia Experimental Design.

Neophobia, an aversive response to novelty, is a behavior with critical ecological and evolutionary relevance for wild populations because it directly influences animals' ability to adapt to new environments and exploit novel resources. Neophobia has been described in a wide variety of different animal species from arachnids to zebra finches. Because of this widespread prevalence and ecological importance, the number of neophobia studies has continued to increase over time. However, many neophobia studies (as well as many animal behavior studies more generally) suffer from one or more of what we have deemed the "seven deadly sins" of neophobia experimental design. These "sins" include: (1) animals that are not habituated to the testing environment, (2) problems with novel stimulus selection, (3) non-standardized motivation, (4) pseudoreplication, (5) lack of sufficient controls, (6) fixed treatment order, and (7) using arbitrary thresholds for data analysis. We discuss each of these potential issues in turn and make recommendations for how to avoid them in future behavior research. More consistency in how neophobia studies are designed would facilitate comparisons across different populations and species and allow researchers to better understand whether neophobia can help explain animals' responses to human-altered landscapes and the ability to survive in the Anthropocene.

Implicit association tests: Stimuli validation from participant responses.

The Implicit Association Test (IAT, Greenwald etal., J. Pers. Soc. Psychol., 74, 1998, 1464) is a popular instrument for measuring attitudes and (stereotypical) biases. Greenwald etal. (Behav. Res. Methods, 54, 2021, 1161) proposed a concrete method for validating IAT stimuli: appropriate stimuli should be familiar and easy to classify - translating to rapid (response times <800 ms) and accurate (error < 10%) participant responses. We conducted three analyses to explore the theoretical and practical utility of these proposed validation criteria. We first applied the proposed validation criteria to the data of 15 IATs that were available via Project Implicit. A bootstrap approach with 10,000 'experiments' of 100 participants showed that 5.85% of stimuli were reliably valid (i.e., we are more than 95% confident that a stimulus will also be valid in a new sample of 18- to 25-year-old US participants). Most stimuli (78.44%) could not be reliably validated, indicating a less than 5% certainty in the outcome of stimulus (in)validity for a new sample of participants. We then explored how stimulus validity differs across IATs. Results show that only some stimuli are consistently (in)valid. Most stimuli show between-IAT variances, which indicate that stimulus validity differs across IAT contexts. In the final analysis, we explored the effect of stimulus type (images, nouns, names, adjectives) on stimulus validity. Stimulus type was a significant predictor of stimulus validity. Although images attain the highest stimulus validity, raw data show large differences within stimulus types. Together, the results indicate a need for revised validation criteria. We finish with practical recommendations for stimulus selection and (post-hoc) stimulus validation.

Early selection of task-relevant features through population gating

Brains can gracefully weed out irrelevant stimuli to guide behavior. This feat is believed to rely on a progressive selection of task-relevant stimuli across the cortical hierarchy, but the specific across-area interactions enabling stimulus selection are still unclear. Here, we propose that population gating, occurring within primary auditory cortex (A1) but controlled by top-down inputs from prelimbic region of medial prefrontal cortex (mPFC), can support across-area stimulus selection. Examining single-unit activity recorded while rats performed an auditory context-dependent task, we found that A1 encoded relevant and irrelevant stimuli along a common dimension of its neural space. Yet, the relevant stimulus encoding was enhanced along an extra dimension. In turn, mPFC encoded only the stimulus relevant to the ongoing context. To identify candidate mechanisms for stimulus selection within A1, we reverse-engineered low-rank RNNs trained on a similar task. Our analyses predicted that two context-modulated neural populations gated their preferred stimulus in opposite contexts, which we confirmed in further analyses of A1. Finally, we show in a two-region RNN how population gating within A1 could be controlled by top-down inputs from PFC, enabling flexible across-area communication despite fixed inter-areal connectivity.

Engineering mechanoreceptor feature selectivity

Touch and proprioception rely on the discriminative abilities of distinct classes of mechanosensory neurons. In this issue of Neuron, two studies1,2 provide evidence that biomechanical mechanisms and ultrastructural cellular specializations are key contributors in defining mechanoreceptor stimulus threshold and selectivity.

Increased display complexity reveals effects of salience in action control.

In action-control research, typically, stimulus sparse displays are used. This might be one reason why previous theorizing focuses on the (top-down) demands of response selection (e.g., what key to press), while often ignoring (bottom-up) demands of stimulus selection (e.g., what stimulus to attend). However, complex perceptual situations may pose selection demands that make additional, response-unrelated feature dimensions relevant for response selection. The major stimulus characteristic affecting perceptual selection is salience. In research on visual attention, there is a debate about the conditions under which salience becomes effective. We related both debates in two experiments, in which we modulated display set size as well as salience in a stimulus-response binding task. In sum, the data of these experiments (pooled N = 138) demonstrated that salience furthered the integration of stimulus features in displays with many stimuli more than in sparse displays. Our results demonstrate the neglected impact of salience on action-control when going beyond the very simplistic displays common in action-control research. (PsycInfo Database Record (c) 2023 APA, all rights reserved).

Distinct competitive impacts of palatability of taste stimuli on sampling dynamics during a preference test.

Food or taste preference tests are analogous to naturalistic decisions in which the animal selects which stimuli to sample and for how long to sample them. The data acquired in such tests, the relative amounts of the alternative stimuli that are sampled and consumed, indicate the preference for each. While such preferences are typically recorded as a single quantity, an analysis of the ongoing sampling dynamics producing the preference can reveal otherwise hidden aspects of the decision-making process that depend on its underlying neural circuit mechanisms. Here, we perform a dynamic analysis of two factors that give rise to preferences in a two-alternative task, namely the distribution of durations of sampling bouts of each stimulus and the likelihood of returning to the same stimulus or switching to the alternative-that is, the transition probability-following each bout. The results of our analysis support a specific computational model of decision making whereby an exponential distribution of bout durations has a mean that is positively correlated with the palatability of that stimulus but also negatively correlated with the palatability of the alternative. This impact of the alternative stimulus on the distribution of bout durations decays over a timescale of tens of seconds, even though the memory of the alternative stimulus lasts far longer-long enough to impact the transition probabilities upon ending bouts. Together, our findings support a state transition model for bout durations and suggest a separate memory mechanism for stimulus selection. (PsycInfo Database Record (c) 2023 APA, all rights reserved).

Picture naming test: Linguistic challenges of the method and ways to solve them

The paper considers benefits and drawbacks of the Picture Naming Test (PNT) as a diagnostic method suggesting the ways to improve its diagnostic and research validity. Although this test is popular in both national and international neuropsychological assessment and research practice, its use is largely due to tradition and practical convenience. However, theoretical underpinnings for its effectiveness are not sufficiently represented in the pertinent literature, which determines the relevance of the study. The major objective of the paper is to consider the PNT as a research technique from the point of view of psycholinguistics, cognitive science, and corpus linguistics and to propose integrated approaches for the further development of these tests. The material comprises picture naming tests developed for the Russian and English languages. The study sets the following aims: 1) to define the main features of PNT and the principles of its application viewed from a historical perspective; 2) to identify the theoretical foundations (linguistic and neuropsychological) for its use as a diagnostic tool; 3) to highlight the problematic aspects of the method; 4) to suggest possible ways to eliminate them. To accomplish these tasks, various methods of corpus linguistics are applied throughout the article. The historical outline of PNT development suggests that the current design might stem from earlier contexts of use. A review of existing models of lexical access provides a theoretical basis for the test in its current form and suggests possible avenues for its development grounded in experimental research, advances in linguistics and big data analysis. A separate section of the article presents critique of the most popular tests. Finally, the analysis of the existing English and Russian tests through the corpus-based methodology clearly demonstrates the need for more detailed norming and stimuli selection. By way of conclusion the authors outline the principles of designing Picture Naming Tests for specific purposes and put forward a step-by-step algorithm that enables careful selection of the necessary indicators and parameters.

Extrapolation of affective norms using transformer-based neural networks and its application to experimental stimuli selection.

Data on the emotionality of words is important for the selection of experimental stimuli and sentiment analysis on large bodies of text. While norms for valence and arousal have been thoroughly collected in English, most languages do not have access to such large datasets. Moreover, theoretical developments lead to new dimensions being proposed, the norms for which are only partially available. In this paper, we propose a transformer-based neural network architecture for semantic and emotional norms extrapolation that predicts a whole ensemble of norms at once while achieving state-of-the-art correlations with human judgements on each. We improve on the previous approaches with regards to the correlations with human judgments by Δr = 0.1 on average. We precisely discuss the limitations of norm extrapolation as a whole, with a special focus on the introduced model. Further, we propose a unique practical application of our model by proposing a method of stimuli selection which performs unsupervised control by picking words that match in their semantic content. As the proposed model can easily be applied to different languages, we provide norm extrapolations for English, Polish, Dutch, German, French, and Spanish. To aid researchers, we also provide access to the extrapolation networks through an accessible web application.

Emergence of a three-sample conditional discrimination as foundation for reasoning capabilities.

We hypothesized that a three-sample conditional discrimination can emerge as a result of learning conditional discriminations with relational stimuli. After learning three first-order conditional discriminations AB, PQ, and CD, we taught a second-order conditional discrimination XAB in which X1 indicated selection of related stimuli (e.g., A1 and B1) and X2 of unrelated stimuli (e.g., A1 and B2). Then, we probed the emergence of conditional discriminations PQX and XCD in which the X stimuli were comparisons and contextual stimuli, respectively. Finally, a conditional discrimination was probed with stimuli P, Q, and C as samples and D1 and D2 as comparisons. When the P and Q stimuli were related (and related to X1 in PQX), all participants selected the D stimulus that was related to the C stimulus (D1 when C1 was present and D2 when C2 was present); when the P and Q stimuli were unrelated (and related to X2 in PQX), they selected the D stimulus unrelated to the C stimulus (D2 when C1 and D1 when C2), which demonstrated emergence based on the relations established among all stimuli. In Experiment 2, the teaching of XAB was omitted and only one in six participants demonstrated emergence, which indicated that relational stimuli X1 and X2 played an important role in emergence. Thus, a new type of emergence that mimics analogical reasoning was demonstrated. The obtained outcome suggests that this procedure provides a learning foundation for acquiring reasoning capabilities.

The Unconscious Tug-of-War: Exploring the Effect of Stimulus Selection Bias on Creative Problem Solving with Multiple Unconscious Stimuli.

This study innovatively investigated the potential selection bias involved in processing multiple subliminal stimuli during creative problem-solving (CPS). It addresses the existing gap in specialized research on how the handling of multiple unconscious stimuli influences higher-order cognitive processes, particularly creativity. The study utilized a masked priming paradigm and a remote association task (RAT). Two experiments were conducted. Experiment 1 presented two stimuli simultaneously, with one being the correct answer, to examine whether there was a bias in the location of subliminal stimuli. In Experiment 2, two stimuli were presented sequentially, with one serving as the answer, to investigate whether there was a temporal bias in unconscious processing. Our findings revealed that when solving easy RATs, subliminal stimuli presented on the left side had a negative priming effect compared to the right side. The results revealed that unconscious processing of subliminal stimuli enhanced performance on difficult CPS. Additionally, a temporal bias was observed, with more recent subliminal stimuli having a stronger effect than earlier stimuli. Unconscious processing can improve CPS, especially for difficult tasks, and there is a bias towards processing stimuli on the left and more recently presented stimuli. These findings contribute to our understanding of unconscious processing, particularly the processing of multiple subliminal stimuli in CPS, and provide insights into the biases that exist in unconscious processing.

Evaluating two iterations of a paired stimulus preference assessment

AbstractThe paired stimulus preference assessment (PSPA) is commonly used in both research and practice. However, two iterations have been described: a single‐presentation arrangement in which each tested stimulus is paired with one another once and a double‐presentation arrangement in which each tested stimulus is paired twice with counterbalanced placement. Each arrangement may have different advantages; however, no direct comparison exists. Thus, the purpose of the current study was to conduct both PSPA iterations to determine whether there are differences in the results obtained and which iteration was most efficient regarding time to administer. Seven participants were included, and results demonstrated high degrees of correspondence across preference assessment formats. The average time to administer the single‐presentation PSPA (M =6.6 min) was almost half the time to administer a double‐presentation PSPA (M =12.9 min), and no significant differences were observed for problem behavior, side biases, or latency to stimulus selection.

Bayesian adaptive method for estimating speed-accuracy tradeoff functions of multiple task conditions.

The speed-accuracy tradeoff (SAT) often makes psychophysical data difficult to interpret. Accordingly, the SAT experimental procedure and model were proposed for an integrated account of the speed and accuracy of responses. However, the extensive data collection for a SAT experiment has blocked its popularity. For a quick estimation of SAT function (SATf), we previously developed a Bayesian adaptive SAT method, including an online stimulus selection strategy. By simulations, the method was proved efficient with high accuracy and precision with minimal trials, adequate for practically applying a single condition task. However, it calls for extensions to more general designs with multiple conditions and should be revised to achieve improved estimation performance. It also demands real experimental validation with human participants. In the current study, we suggested an improved method to measure SATfs for multiple task conditions concurrently and to enhance robustness in general designs. The performance was evaluated with simulation studies and a psychophysical experiment using a flanker task. Simulation results revealed that the proposed method with the adaptive stimulus selection strategy efficiently estimated multiple SATfs and improved performance even for cases with an extreme parameter value. In the psychophysical experiment, SATfs estimated by minimal adaptive trials (1/8 of conventional trials) showed high agreement with those by conventional trials required for reliably estimating multiple SATfs. These results indicate that the Bayesian adaptive SAT method is reliable and efficient in estimating SATfs in most experimental settings and may apply to SATf estimation in general behavioral research designs.

Statistical learning facilitates the selection of stimuli into awareness

Statistical learning facilitates the selection of stimuli into awareness

Serial dependence improves performance and biases confidence-based decisions.

Perception depends on both the current sensory input and on the preceding stimuli history, a mechanism referred to as serial dependence (SD). One interesting, and somewhat controversial, question is whether serial dependence originates at the perceptual stage, which should lead to a sensory improvement, or at a subsequent decisional stage, causing solely a bias. Here, we studied the effects of SD in a novel manner by leveraging on the human capacity to spontaneously assess the quality of sensory information. Two noisy-oriented Gabor stimuli were simultaneously presented along with two bars of the same orientation as the Gabor stimuli. Participants were asked to choose which Gabor stimulus to judge and then make a forced-choice judgment of its orientation by selecting the appropriate response bar. On all trials, one of the Gabor stimuli had the same orientation as the Gabor in the same position on the previous trial. We explored whether continuity in orientation and position affected choice and accuracy. Results show that continuity of orientation leads to a persistent (up to four back) accuracy advantage and a higher preference in the selection of stimuli with the same orientation, and this advantage accumulates over trials. In contrast, analysis of the continuity of the selected position indicated that participants had a strong tendency to choose stimuli in the same position, but this behavior did not lead to an improvement in accuracy.

Internal selective attention is delayed by competition between endogenous and exogenous factors

External attention is mediated by competition between endogenous (goal-driven) and exogenous (stimulus-driven) factors, with the balance of competition determining which stimuli are selected. Occasionally, exogenous factors "win" this competition and drive the selection of task-irrelevant stimuli. Endogenous and exogenous selection mechanisms may also compete to control the selection of internal representations (e.g., those stored in working memory), but whether this competition is resolved in the same way as external attention is unknown. Here, we leveraged the high temporal resolution of human EEG to determine how competition between endogenous and exogenous factors influences the selection of internal representations. Unlike external attention, competition did not prompt the selection of task-irrelevant working memory content. Instead, it delayed the endogenous selection of task-relevant working memory content by several hundred milliseconds. Thus, competition between endogenous and exogenous factors influences internal selective attention, but in a different way than external selective attention.

The use of Active Learning systems for stimulus selection and response modelling in perception experiments

To study the role of perceptual cues on categorization and decision making, participants are typically tested in (perception) experiments with a fixed set of randomized or pseudo-randomized trials. In linguistics and psycholinguistics, for instance, studies often investigate the relative weighting of different cues for a linguistic contrast (e.g., intonation vs. word order). For categorization beyond the segmental level (e.g., /p/ vs. /b/), it is important to establish that results generalise to different words or sentences, which necessitates the use of a range of different items. This may limit the number of conditions (cues and cue combinations) that can be sensibly tested in the same experiment. We show that Active Learning (AL) systems provide a solution: Since stimulus selection is informed by the system's learning mechanism (presenting certain conditions less often than uncertain conditions), they allow for efficient testing of numerous conditions and different items in the same experiment. In this paper, we compared two weighting approaches (average probability-based vs. regression-based) to model the outcome of three simulated scenarios with three binary factors each. Results show that valid results (i.e., little error between predicted values and the actual responses at the end of the experiment) are obtained after about a third of the trials of an original psycholinguistic experiment we replicated. For simulations with interactions between factors, the regression-based approach performed better. Our findings bear implications for the application of AL in psycholinguistic research (extraction of cue weights, inferential statistics, and a stopping criterion during an on-going experiment), which we will discuss.

Criticality and Neuromorphic Sensing in a Single Memristor.

Resistive random access memory (RRAM) is an important technology for both data storage and neuromorphic computation, where the dynamics of nanoscale conductive filaments lies at the core of the technology. Here, we analyze the current noise of various silicon-based memristors that involves the creation of a percolation path at the intermediate phase of filament growth. Remarkably, we find that these atomic switching events follow scale-free avalanche dynamics with exponents satisfying the criteria for criticality. We further prove that the switching dynamics are universal and show little dependence on device sizes or material features. Utilizing criticality in memristors, we simulate the functionality of hair cells in auditory sensory systems by observing the frequency selectivity of input stimuli with tunable characteristic frequency. We further demonstrate a single-memristor-based sensing primitive for representation of input stimuli that exceeds the theoretical limits dictated by the Nyquist-Shannon theorem.