Conjunction Of Features Research Articles

Stability of cross-sensory input to primary somatosensory cortex across experience

Merging information across sensory modalities is key to forming robust percepts, yet how the brain achieves this feat remains unclear. Recent studies report cross-modal influences in the primary sensory cortex, suggesting possible multisensory integration in the early stages of cortical processing. We test several hypotheses about the function of auditory influences on mouse primary somatosensory cortex (S1) using invivo two-photon calcium imaging. We found sound-evoked spiking activity in an extremely small fraction of cells, and this sparse activity did not encode auditory stimulus identity. Moreover, S1 did not encode information about specific audio-tactile feature conjunctions. Auditory and audio-tactile stimulus encoding remained unchanged after both passive experience and reinforcement. These results suggest that while primary sensory cortex is plastic within its own modality, the influence of other modalities is remarkably stable and stimulus nonspecific.

Stability of cross-sensory input to primary somatosensory cortex across experience.

Merging information from across sensory modalities is key to forming robust, disambiguated percepts of the world, yet how the brain achieves this feat remains unclear. Recent observations of cross-modal influences in primary sensory cortical areas have suggested that multisensory integration may occur in the earliest stages of cortical processing, but the role of these responses is still poorly understood. We address these questions by testing several hypotheses about the possible functions served by auditory influences on the barrel field of mouse primary somatosensory cortex (S1) using in vivo 2-photon calcium imaging. We observed sound-evoked spiking activity in a small fraction of cells overall, and moreover that this sparse activity was insufficient to encode auditory stimulus identity; few cells responded preferentially to one sound or another, and a linear classifier trained to decode auditory stimuli from population activity performed barely above chance. Moreover S1 did not encode information about specific audio-tactile feature conjunctions that we tested. Our ability to decode auditory audio-tactile stimuli from neural activity remained unchanged after both passive experience and reinforcement. Collectively, these results suggest that while a primary sensory cortex is highly plastic with regard to its own modality, the influence of other modalities are remarkably stable and play a largely stimulus-non-specific role.

Dynamic retrieval of events and associations from memory: An integrated account of item and associative recognition.

Memory theories distinguish between item and associative information, which are engaged by different tasks: item recognition uses item information to decide whether an event occurred in a particular context; associative recognition uses associative information to decide whether two events occurred together. Associative recognition is slower and less accurate than item recognition, suggesting that item and associative information may be represented in different forms and retrieved using different processes. Instead, I show how a dynamic model (Cox & Criss, 2020; Cox & Shiffrin, 2017) accounts for accuracy and response time distributions in both item and associative recognition with the same set of representations and processes. Item and associative information are both represented as vectors of features. Item and associative recognition both depend on comparing traces in memory with probes of memory in which item and associative features gradually accumulate. Associative features are slower to accumulate, but largely because they emerge from conjunctions of already-accumulated item features. I apply the model to data from 453 participants, each of whom performed an item and performed associative recognition following identical study conditions (Cox et al., 2018). Comparisons among restricted versions of the model show that its account of associative feature formation, coupled with limits on the rate at which features accumulate from multiple items, explains how and why the dynamics of associative recognition differ from those of item recognition even while both tasks rely on the same underlying representations. (PsycInfo Database Record (c) 2024 APA, all rights reserved).

Industrially compatible synthesis of MCM-41 with spatial organization at the macro-mesoscale

Nowadays industrial requirements point to high-performance processes but cost-effective materials to maximize their benefit/cost balance. This paper describes the properties of a macro-mesoporous MCM-41 silica with very high surface area obtained from inexpensive reagents —industrial sodium silicate as a source of silicon and industrial CTAC as template— with potential use in an environmental application such as CO2 capture. The MCM-41 silica exhibits an aperiodic 3D hierarchical spatial organization at the macro-mesoscale, formed by well-ordered MCM-41 particles with bowl-like mesopores. These particles are interconnected in three dimensions, creating a web-like structure that imparts macroporosity. This organization can be rationalized in terms of the nature and interaction of the reactants. Thus, the conjunction of poly (N-silicate) and features in CTAC, such as the weakly bonding counterion (Cl−), ethanol and unreacted amine, gave rise to different morphologies and variable channel lengths, porosity at different length scales producing meso/macro arrangements, and a spongy structure as a disordered minority phase. The hierarchical organization enhances the potential of the material for uniform APTS loading, thereby improving CO2 capture. Then the use of industrial reactants offers two important advantages: (i) The presence of macro-mesocavities, enabling applications requiring greater porosity than that intrinsic to MCM-41; (ii) A reduction in production costs by at least 80 % compared to traditional synthesis methods using alkoxysilanes and CTAB, and negligible costs compared to synthesis with analytical grade CTAC.In summary, this study demonstrates the synthesis of a hierarchically structured MCM-41 silica using cost-effective industrial reagents, offering a promising and economical solution for different applications.

Visual perceptual learning of feature conjunctions leverages non-linear mixed selectivity

Visual objects are often defined by multiple features. Therefore, learning novel objects entails learning feature conjunctions. Visual cortex is organized into distinct anatomical compartments, each of which is devoted to processing a single feature. A prime example are neurons purely selective to color and orientation, respectively. However, neurons that jointly encode multiple features (mixed selectivity) also exist across the brain and play critical roles in a multitude of tasks. Here, we sought to uncover the optimal policy that our brain adapts to achieve conjunction learning using these available resources. 59 human subjects practiced orientation-color conjunction learning in four psychophysical experiments designed to nudge the visual system towards using one or the other resource. We find that conjunction learning is possible by linear mixing of pure color and orientation information, but that more and faster learning takes place when both pure and mixed selectivity representations are involved. We also find that learning with mixed selectivity confers advantages in performing an untrained “exclusive or” (XOR) task several months after learning the original conjunction task. This study sheds light on possible mechanisms underlying conjunction learning and highlights the importance of learning by mixed selectivity.

Attentional Modulation in Early Visual Cortex: A Focused Reanalysis of Steady-state Visual Evoked Potential Studies.

Steady-state visual evoked potentials (SSVEPs) are a powerful tool for investigating selective attention. Here, we conducted a combined reanalysis of multiple studies employing this technique in a variety of attentional experiments to, first, establish benchmark effect sizes of attention on amplitude and phase of SSVEPs and, second, harness the power of a large data set to test more specific hypotheses. Data of eight published SSVEP studies were combined, in which human participants (n = 135 in total) attended to flickering random dot stimuli based on their defining features (e.g., location, color, luminance, or orientation) or feature conjunctions. The reanalysis established that, in all the studies, attention reliably enhanced amplitudes, with color-based attention providing the strongest effect. In addition, the latency of SSVEPs elicited by attended stimuli was reduced by ∼4 msec. Next, we investigated the modulation of SSVEP amplitudes in a subset of studies where two different features were attended concurrently. Although most models assume that attentional effects of multiple features are combined additively, our results suggest that neuronal enhancement provided by concurrent attention is better described by multiplicative integration. Finally, we used the combined data set to demonstrate that the increase in trial-averaged SSVEP amplitudes with attention cannot be explained by increased synchronization of single-trial phases. Contrary to the prediction of the phase-locking account, the variance across trials of complex Fourier coefficients increases with attention, which is more consistent with boosting of a largely phase-locked signal embedded in non-phase-locked noise.

Do cultural differences emerge at different levels of representational hierarchy?

In prior research, Eastern and Western culture groups differ in memory specificity for objects. However, these studies used concrete object stimuli, which carry semantic information that may be confounded with culture. Additionally, the perceptual properties of the stimuli were not tightly controlled. Therefore, it cannot be precisely determined whether the observed cross-cultural differences are generalizable across different stimulus types and memory task demands. In prior studies, Americans demonstrated higher memory specificity than East Asians, but this may be due to Americans being more attuned to the low-level features that distinguish studied items from similar lures, rather than general memory differences. To determine whether this pattern of cross-cultural memory differences emerges irrespective of stimulus properties, we tested American and East Asian young adults using a recognition memory task employing abstract stimuli for which attention to conjunctions of features was critical for discrimination. Additionally, in order to more precisely determine the influence of stimulus and task on culture differences, participants also completed a concrete objects memory task identical to the one used in prior research. The results of the abstract objects task mirror the pattern seen in prior studies with concrete objects: Americans showed generally higher levels of recognition memory performance than East Asians for studied abstract items, whether discriminating them from similar or entirely new items. Results from the current concrete object task generally replicated this pattern. This suggests cross-cultural memory differences generalize across stimulus types and task demands, rather than reflecting differential sensitivity to low-level features or higher-level conjunctions.

The locus of recognition memory signals in human cortex depends on the complexity of the memory representations.

According to a "Swiss Army Knife" model of the brain, cognitive functions such as episodic memory and face perception map onto distinct neural substrates. In contrast, representational accounts propose that each brain region is best explained not by which specialized function it performs, but by the type of information it represents with its neural firing. In a functional magnetic resonance imaging study, we asked whether the neural signals supporting recognition memory fall mandatorily within the medial temporal lobes (MTL), traditionally thought the seat of declarative memory, or whether these signals shift within cortex according to the content of the memory. Participants studied objects and scenes that were unique conjunctions of pre-defined visual features. Next, we tested recognition memory in a task that required mnemonic discrimination of both simple features and complex conjunctions. Feature memory signals were strongest in posterior visual regions, declining with anterior progression toward the MTL, while conjunction memory signals followed the opposite pattern. Moreover, feature memory signals correlated with feature memory discrimination performance most strongly in posterior visual regions, whereas conjunction memory signals correlated with conjunction memory discrimination most strongly in anterior sites. Thus, recognition memory signals shifted with changes in memory content, in line with representational accounts.

Similarity and structured representation in human and nonhuman apes

How we judge the similarity between objects in the world is connected ultimately to how we represent those objects. It has been argued extensively that object representations in humans are ‘structured’ in nature, meaning that both individual features and the relations between them can influence similarity. In contrast, popular models within comparative psychology assume that nonhuman species appreciate only surface-level, featural similarities. By applying psychological models of structural and featural similarity (from conjunctive feature models to Tversky's Contrast Model) to visual similarity judgements from adult humans, chimpanzees, and gorillas, we demonstrate a cross-species sensitivity to complex structural information, particularly for stimuli that combine colour and shape. These results shed new light on the representational complexity of nonhuman apes, and the fundamental limits of featural coding in explaining object representation and similarity, which emerge strikingly across both human and nonhuman species.

Correlation Analysis of Trace Element Content in Caustobioliths: The Deep Fluid Involvement, Conjunction of Features of Organic and Inorganic Models of Oil Genesis

Correlation Analysis of Trace Element Content in Caustobioliths: The Deep Fluid Involvement, Conjunction of Features of Organic and Inorganic Models of Oil Genesis

A feature and conjunction visual search immersive virtual reality serious game for measuring spatial and distractor inhibition attention using response time and action kinematics

ABSTRACT Background Treisman (1980) proposed that visual-spatial attention to targets presented with distractors involves parallel and serial cognition. When the target is different from distractors by a single feature, the number of distractors does not influence search speed (parallel). However, when the target is different from the distractor by a conjunction of features, increased numbers of distractors increase task difficulty (serial). Here, we developed a serious game in immersive virtual reality (IVR) for evaluating spatial and distractor inhibition attention. Methods We tested 60 healthy participants. They performed the serious game in which they had to find a target mole wearing a red miner’s helmet. In the single feature parallel conditions, the distractor moles wore blue (miner’s or horned) helmets, and in the conjunction feature serial conditions, the distractor moles wore blue miner’s helmets or red horned helmets. There were 11–17–23 distractors. Responses were made with the dominant hand by hitting the target with a virtual hammer. We measured mean response time (RT), mean velocity (MV) and coefficient of variance of speed (CV). Results Participants were significantly slower (RT and MV) and showed greater CV when responding to targets in conjunction compared to single feature search tasks. Further, participants were slower (RT and MV) and showed greater CV when the number of distractors increased. A significant interaction between search tasks and distractors showed that RT and CV only increased with distractor number for the conjunction search tasks. MV decreased with distractor number for both single and conjunction tasks, with a stronger decrease for conjunction relative to single feature search. Conclusion The results replicated previous findings, providing support for the use of immersive virtual reality technology for the simultaneous evaluation of spatial and distractor inhibition attention using complex 3D objects.

Role of time in binding features in visual working memory.

Previous research on feature binding in visual working memory has supported a privileged role for location in binding an object's nonspatial features. However, humans are able to correctly recall feature conjunctions of objects that occupy the same location at different times. In a series of behavioral experiments, we investigated binding errors under these conditions, and specifically tested whether ordinal position can take the role of location in mediating feature binding. We performed two dual report experiments in which participants had to memorize three colored shapes presented sequentially at the screen center. When participants were cued with the ordinal position of one item and had to report its shape and color, report errors for the two features were largely uncorrelated. In contrast, when participants were cued, for example, with an item's shape and reported an incorrect ordinal position, they had a high chance of making a corresponding error in the color report. This pattern of error correlations closely matched the predictions of a model in which color and shape are bound to each other only indirectly via an item's ordinal position. In a third experiment, we directly compared the roles of location and sequential position in feature binding. Participants viewed a sequence of colored disks displayed at different locations and were cued either by a disk's location or its ordinal position to report its remaining properties. The pattern of errors supported a mixed strategy with individual variation, suggesting that binding via either time or space could be used for this task. (PsycInfo Database Record (c) 2023 APA, all rights reserved).

Attentional disengagement effect based on relevant features.

In visual search tasks, distractors similar to the target can attract our attention and affect the speed of attentional disengagement. The attentional disengagement refers to shifting attention away from stimuli that are not relevant to the task. Previous studies mainly focused on the attentional disengagement of one feature dimension. However, the mechanisms of different feature dimensions on attentional disengagement in single and conjunction visual search remain unclear. In the current study, we adopted the oculomotor disengagement paradigm and used saccade latency as an indicator to explore the effects of different feature dimensions of center stimuli on attentional disengagement. In both single and conjunction feature search tasks, participants began each search by fixating on a center stimulus that appeared simultaneously with search display but would not be the target. Participants were instructed to ensure the first saccade to the target location. In Experiments 1A (single feature search) and 1B (conjunction feature search), we found that the attentional disengagement was significantly delayed or accelerated when center stimuli shared color features with the target or salient distractor, but not in shape feature. Moreover, we found that the difference between the two feature dimensions might be caused by their different search difficulty (Experiment 1C). Therefore, in Experiment 2, we matched the difficulty of searching for color and shape tasks before exploring whether there were differences in the effects of different feature dimensions on attentional disengagement. However, the results in Experiment 2 were similar to those in Experiment 1A, indicating that the different effects of feature dimensions on attentional disengagement were caused by feature asymmetry. Therefore, in Experiment 3, we improved the salient discernibility of shape dimension and matched color search to it. The results showed that although the attentional disengagement was delayed in shape dimension, it was still smaller than that in color dimension. Our results supported that goal-oriented attention sets were the main cause of delayed attentional disengagement. By series of experiments, we found that the utilization of different feature dimensions was associated with task difficulty and the features asymmetry in both single and conjunction visual search.

Cohesive Devices on the Abstracts of Select Research Articles Presented in the International Academic Forum (AIFOR): A Discourse Analysis

This linguistic research analysis investigates the cohesive devices found in the Abstract of select Asian Conference of Education 2019 research articles. This study also endeavors to disclose the contributions of the cohesive devices in the comprehensibility of the text. This corpus-based study utilizes qualitative descriptive research that specifically employs the evocative discourse analysis. It considers the use of Halliday and Hassan’s taxonomy on Cohesive devices as a basis for investigation. A total of twenty-eight (28) research abstracts are chosen from abstracts compiled in the program and abstract book of the Asian Conference on Education (ACE) presented during the International Academic Forum (IAFOR) held in Toshi Hotel, Tokyo, Japan last October 31 to November 3, 2019, as the main source of data. The data are analyzed using Halliday and Hasan’s taxonomy of cohesion which is divided into two aspects, grammatical and lexical cohesion. The result of the study reveals that researchers utilize two grammatical cohesions namely: reference and conjunctions in their research abstracts. The conjunctive features of the grammatical device found are additive, causal, adversative, and temporal. Moreover, the referential grammatical devices found are demonstrative, personal, article, and comparative. There is no usage of substitution and elliptical cohesion or ellipsis found. In terms of lexical cohesion, Reiteration devices such as repetition, synonymy, and antonymy are utilized by the researchers in their abstracts. There is no evidence of meronomy found in the analysis. Collocation devices are widely used in the abstract. In the analysis, the presence of the cohesive devices in the abstracts functions to keep track of the participants, organized in logical order the concepts in the abstract, and help in avoiding repetition and text redundancy which significantly contributes to the text comprehensibility of the research abstracts. Thus, the researcher designs and presents an English workbook for classroom use in which the drills provided focus on the correct usage of cohesive devices in any written discourse.

Cohesive Devices on the Abstracts of Select Research Articles Presented in the International Academic Forum (AIFOR): A Discourse Analysis

This linguistic research analysis investigates the cohesive devices found in the Abstract of select Asian Conference of Education 2019 research articles. This study also endeavors to disclose the contributions of the cohesive devices in the comprehensibility of the text. This corpus-based study utilizes qualitative descriptive research that specifically employs the evocative discourse analysis. It considers the use of Halliday and Hassan’s taxonomy on Cohesive devices as a basis for investigation. A total of twenty-eight (28) research abstracts are chosen from abstracts compiled in the program and abstract book of the Asian Conference on Education (ACE) presented during the International Academic Forum (IAFOR) held in Toshi Hotel, Tokyo, Japan last October 31 to November 3, 2019, as the main source of data. The data are analyzed using Halliday and Hasan’s taxonomy of cohesion which is divided into two aspects, grammatical and lexical cohesion. The result of the study reveals that researchers utilize two grammatical cohesions namely: reference and conjunctions in their research abstracts. The conjunctive features of the grammatical device found are additive, causal, adversative, and temporal. Moreover, the referential grammatical devices found are demonstrative, personal, article, and comparative. There is no usage of substitution and elliptical cohesion or ellipsis found. In terms of lexical cohesion, Reiteration devices such as repetition, synonymy, and antonymy are utilized by the researchers in their abstracts. There is no evidence of meronomy found in the analysis. Collocation devices are widely used in the abstract. In the analysis, the presence of the cohesive devices in the abstracts functions to keep track of the participants, organized in logical order the concepts in the abstract, and help in avoiding repetition and text redundancy which significantly contributes to the text comprehensibility of the research abstracts. Thus, the researcher designs and presents an English workbook for classroom use in which the drills provided focus on the correct usage of cohesive devices in any written discourse.

Serial dependence occurs at the level of both features and integrated object representations.

Object perception depends on mechanisms that transform the information received by our sensory receptors into a coherent and meaningful experience. Visual objects are made up of visual features (e.g., shape, color, orientation), which are, in large part, processed in parallel across different brain areas. The experience of unified objects thus requires binding features and brain signals. Our perception of objects is remarkably stable and constant, despite changes in the proximal stimulus caused by eye and body movements or changes in ambient lighting. Such spurious changes are not perceived. Object perception thus also depends on a mechanism that smooths perceptual samples across time, which has been called the continuity field and is quantified by serial dependence. In two studies, the relative levels of feature binding and serial dependence were examined. Participants reported perceived shape or emotional expression; reports were attracted to stimuli seen in the recent past. Results further show that serial dependence occurs both at the level of features and at the level of objects defined by a conjunction of features. The relative level of serial dependence depends on the type of feature or object: Serial dependence of shape occurs mostly independently of other features that define an object, whereas serial dependence of emotional expression occurs on the object-level representation that integrates several features. (PsycInfo Database Record (c) 2022 APA, all rights reserved).

Task demands determine whether shape or arousal of a stimulus modulates competition for visual working memory resources

It has been posited (Öhman, 1986) that the processing of threatening stimuli became prioritized during the course of mammalian evolution and that such objects may still enjoy an advantage in visual processing to this day. It has been well-documented that both mid-level visual features (i.e., conjunctions of low-level features) and the arousal level of threatening stimuli affect attentional allocation (Cisler & Koster, 2010; Wolfe & Horowitz, 2004). Despite this, few studies have investigated the effect these factors have on visual working memory resources. Here, we investigated these factors using a rapid serial visual presentation (RSVP) paradigm, and by manipulating mid-level features (specifically, shape: similar vs. dissimilar) and the arousal level (non-threatening vs threatening) of the stimuli. Participants watched an RSVP stream in preparation for an upcoming memory test. Then, they completed a two-alternative forced-choice recognition memory test (with semantically matched foils) wherein they had to identify which item they had seen in the RSVP stream. Our results showed that when shape was a sufficient feature to discriminate the target from the other items in the stream, there was no effect of arousal (i.e., threat level) on reaction time or accuracy during the memory test. However, when the shapes of all the stimuli in the visual stream were highly similar, an effect of arousal appeared: When the target had a different arousal level than the background items (i.e., non-targets), performance was improved. Together, the results suggest that both mid-level visual features and arousal level can modulate competition for visual working memory resources.

A failure to learn object shape geometry: Implications for convolutional neural networks as plausible models of biological vision

Here we examine the plausibility of deep convolutional neural networks (CNNs) as a theoretical framework for understanding biological vision in the context of image classification. Recent work on object recognition in human vision has shown that both global, and local, shape information is computed, and integrated, early during perceptual processing. Our goal was to compare the similarity in how object shape information is processed by CNNs and human observers. We tested the hypothesis that, unlike the human system, CNNs do not compute representations of global and local object geometry during image classification. To do so, we trained and tested six CNNs (AlexNet, VGG-11, VGG-16, ResNet-18, ResNet-50, GoogLeNet), and human observers, to discriminate geometrically possible and impossible objects. The ability to complete this task requires computation of a representational structure of shape that encodes both global and local object geometry because the detection of impossibility derives from an incongruity between well-formed local feature conjunctions and their integration into a geometrically well-formed 3D global shape. Unlike human observers, none of the tested CNNs could reliably discriminate between possible and impossible objects. Detailed analyses using gradient-weighted class activation mapping (GradCam) of CNN image feature processing showed that network classification performance was not constrained by object geometry. In contrast, if classification could be made based solely on local feature information in line drawings the CNNs were highly accurate. We argue that these findings reflect fundamental differences between CNNs and human vision in terms of underlying image processing structure. Notably, unlike human vision, CNNs do not compute representations of object geometry. The results challenge the plausibility of CNNs as a framework for understanding image classification in biological vision systems.

Effects of All-Night Driving on Selective Attention in Professional Truck Drivers: A Preliminary Functional Magnetic Resonance Study

Fatigue affects multiple aspects of cognitive performance among drivers. However, even after fatigue builds up, some are still able to maintain the level of behavioral performance. To evaluate these adaptations on the neural network level, we utilized functional magnetic resonance imaging (fMRI). Seventeen male professional drivers underwent two fMRI sessions, once while rested and once in a fatigued condition after 10-h of overnight driving. The cognitive task used in the study involved the detection of visual feature conjunctions, namely the shape and the color. There were no significant differences in the task performance between the conditions except for longer reaction times in the fatigued condition. However, we observed substantial differences in the activation patterns during the cognitive task involving selective attention between the conditions. On the global level, we observed a general decrease in activation strength in the fatigued condition, which appeared to be more pronounced in the left hemisphere. On the local level, we observed a (spatially) extended activation of the medial prefrontal regions in the fatigued condition, which reflected increased cognitive control mechanisms compensating for the diminished efficiency of mechanisms involved in meeting task demands.

Feature-based attention processes in primate prefrontal cortex do not rely on feature similarity.

Feature-based attention enables privileged processing of specific visual properties. During feature-based attention, neurons in visual cortices show "gain modulation" by enhancing neuronal responses to the features of attended stimuli due to top-down signals originating from prefrontal cortex (PFC). Attentional modulation in visual cortices requires "feature similarity:" neurons only increase their responses when the attended feature variable and the neurons' preferred feature coincide. However, whether gain modulation based on feature similarity is a general attentional mechanism is currently unknown. To address this issue, we record single-unit activity from PFC of macaques trained to switch attention between two conjunctive feature parameters. We find that PFC neurons experience gain modulation in response to attentional demands. However, this attentional gain modulation in PFC is independent of the feature-tuning preferences of neurons. These findings suggest that feature similarity is not a general mechanism in feature-based attention throughout the cortical processing hierarchy.