Specific Stimulus Features Research Articles

Event-related potential evidence for tactile orientation processing in the human brain

It is well known that information on stimulus orientation plays an important role in sensory processing. However, the neural mechanisms underlying somatosensory orientation perception are poorly understood. Adaptation has been widely used as a tool for examining sensitivity to specific features of sensory stimuli. Using the adaptation paradigm, we measured event-related potentials (ERPs) in response to tactile orientation stimuli presented pseudo-randomly to the right-hand palm in trials with all the same or different orientations. Twenty participants were asked to count the tactile orientation stimuli. The results showed that the adaptation-related N60 component was observed around contralateral central-parietal areas, possibly indicating orientation processing in the somatosensory regions. Conversely, the adaptation-related N120 component was identified bilaterally across hemispheres, suggesting the involvement of the frontoparietal circuitry in further tactile orientation processing. P300 component was found across the whole brain in all conditions and was associated with task demands, such as attention and stimulus counting. These findings help provide an understanding of the mechanisms of tactile orientation processing in the human brain.

Effects of emotion on auditory ERPs are independent of manipulated target relevance.

Emotional attention describes the prioritized processing of emotional information to help humans quickly detect biologically salient stimuli and initiate appropriate reactions. Humans can also voluntarily attend to specific stimulus features that are target-relevant. Electrophysiological studies have shown specific temporal interactions between voluntary and emotional attention, while no such studies exist for natural sounds (e.g., explosions, running water, applause). In two experiments (N = 40, each), we examined event-related potentials (ERPs) toward target relevant or irrelevant negative, neutral, or positive sounds. Target relevance was induced by the instruction to respond blockwise to either negative, neutral, or positive sounds. Emotional sounds elicited increased fronto-central N1 and P2 amplitudes and a larger late positive potential (LPP), with more sustained effects for negative sounds. Target relevance increased amplitudes during an early LPP interval (400-900 ms) but did not interact with the valence of the sounds. These results show early and late ERP modulations for natural sounds, which do not interact with the target relevance of the sound valence, in contrast to findings from the visual domain. Thus, findings indicate little temporal overlap between emotional processes and target relevance effects in the auditory domain. (PsycInfo Database Record (c) 2024 APA, all rights reserved).

A STUDY TO ASSESS THE EFFECTIVENESS OF STROOP TASK PERFORMANCE TO IMPROVE VISUAL PERCEPTUAL DISCRIMINATION AMONG VARIOUS CHILDHOOD DISORDERS AT SELECTED HOME, PUDUCHERRY

Background: The Stroop effect is a simple phenomenon that reveals a lot about the brain processes information. The Stroop effect is our tendency to experience difficulty naming a physical color when it is used to spell the name of a different color. It is a neuropsychological test extensively used to assess the ability to inhibit cognitive interference that occurs when the processing of a specific stimulus feature impedes the simultaneous processing of a second stimulus attribute, well-known as the Stroop Effect. The childhood disorder is an any illness, impairment, or abnormal condition that affects primarily infants and children. Some of the childhood disorders like Mild Mental Retardation, Learning Disorders, Motor Skills Disorders, Pervasive Developmental Disorders, Attention Deficit Hyperactive Disorders, Eating disorders of infancy or early childhood, Tic disorders. Visual perceptual discrimination is the brain’s ability to accurately perceive information in a complex, fluid and confusing situation and, even more importantly, to accurately differentiate amongst confusable types of information and ability to identify detail seeing Items like differences in shape, color and orientation. Objectives: The main purpose of this study is to assess the level of visual perceptual discrimination among various childhood disorders. To evaluate the level of visual perceptual discrimination before and after administration of Stroop task performance among various childhood disorders. To associate the level of visual perceptual discrimination among various childhood disorders with their selected demographic variables. Materials and Methods: The research approach used in the study was Quantitative in nature. Pre –Experimental One group Pre- test Post test design was used. Purposive Sampling technique was used to select the samples. A total of 30 Children’s with various childhood disorders were selected for this study. Visual Perceptual Discrimination checklist was used to assess the Visual Perceptual Discrimination Problems among children with childhood disorder and administering stroop task performance using Flashcard was used for intervention and Post test was conducted by using same tool in same manner. Results and Conclusion: The result showed that majority of the childhood disorders at selected home 26(86.7%) had low and 4(13.3%) had moderate level of visual perceptual discrimination during Pre test. The Calculated paired‘t’ value was t= -8.55 and was found to be statistically significant at -P=<0.001 level. After Intervention majority of childhood disorders at selected home 16(53.3%) had low and 14(46.7%) had moderate level of visual perceptual discrimination. There was area of residence and type of childhood disorders had shown statistically significant association between post testlevel of visual perceptual discrimination among various childhood disorders with their selected demographic variables. The other demographic variable had not shown statistically significant association between the post-test level of visual Perceptual discrimination among various childhood disorders with their selected demographic variables .The researcher concluded that by administering Stroop task performance shows that the intervention helps in improving the level of visual perceptual discrimination in good range and found to be one of the helpful interventions in improving the level of visual perceptual discrimination among children with various childhood disorders. The study had proved that Effectiveness and excellent changes in improvement of visual perceptual discrimination among Children\s with various childhood disorders.

Modelos cognitivos de emoções musicais: abordagens discreta e dimensional

Emotions are biological, chemical, and neural reactions to stimuli, influenced by crucial brain mechanisms for human survival and well-being. Music is linked to the induction of emotions with neurobiological foundations associated with the activation of structures in the limbic and paralimbic systems. The induction of emotions is also related to specific features of mu-sical stimuli. This article aims to discuss the discrete and dimensional approaches to emotions and cognitive models of musical emotions through a literature review. The discrete approach argues that certain emotional categories are universal and innate, reflecting internally trig-gered states driven by genetically programmed bodily changes. The dimensional approach involves models that represent emotions in a few dimensions rather than specific emotional states. Both guide models of musical emotions and enable testing hypotheses and creating emotional assessment tools with music.

Eye movement behavior in a real-world virtual reality task reveals ADHD in children

Eye movements and other rich data obtained in virtual reality (VR) environments resembling situations where symptoms are manifested could help in the objective detection of various symptoms in clinical conditions. In the present study, 37 children with attention deficit hyperactivity disorder and 36 typically developing controls (9–13 y.o) played a lifelike prospective memory game using head-mounted display with inbuilt 90 Hz eye tracker. Eye movement patterns had prominent group differences, but they were dispersed across the full performance time rather than associated with specific events or stimulus features. A support vector machine classifier trained on eye movement data showed excellent discrimination ability with 0.92 area under curve, which was significantly higher than for task performance measures or for eye movements obtained in a visual search task. We demonstrated that a naturalistic VR task combined with eye tracking allows accurate prediction of attention deficits, paving the way for precision diagnostics.

Involvement of the default mode network under varying levels of cognitive effort

Everyday cognitive functioning is characterized by constant alternations between different modes of information processing, driven by constant fluctuations in environmental demands. At the neural level, this is realized through corresponding dynamic shifts in functional activation and network connectivity. A distinction is often made between resting and task processing and between task-negative and task-positive functional networks. The Default Mode Network (DMN) is classically considered as a resting state (i.e. task-negative) network, upregulated in the absence of cognitive demands. In contrast, task-positive networks have been labelled the Extrinsic Mode Network (EMN). We investigated changes in brain activation and functional network connectivity in an experimental situation of repeated alterations between levels of cognitive effort, following a block-design. Using fMRI and a classic Stroop paradigm, participants switched back and forth between periods of no effort (resting), low effort (word reading, i.e. automatic processing based on learned internal representations and rules) and high effort (color naming, i.e. cognitively controlled perceptual processing of specific features of external stimuli). Results showed an expected EMN-activation for task versus resting contrasts, and DMN-activation for rest versus task contrasts. The DMN was in addition more strongly activated during periods of low effort contrasted with high effort, suggesting a gradual up- and down-regulation of the DMN network, depending on the level of demand and the type of processing required. The often reported “anti-correlation” between DMN and EMN was strongest during periods of low effort, indicating intermittent contributions of both networks. Taken together, these results challenge the traditional view of the DMN as solely a task-negative network. Instead, both the EMN and DMN may contribute to low-effort cognitive processing. In contrast, periods of resting and high effort are dominated by the DMN and EMN, respectively.

Binding Error-Induced Control States.

Binding and retrieval of stimulus features, response features, and their attentional weighting tune cognitive processing to situational demands. The two mechanisms promote successful actions, especially in situations in which such actions depend on controlled processing. Here we explored binding and retrieval of attentional control states that follow from erroneous actions. By definition, such errors are characterized by insufficient cognitive control but at the same time, error detection has been shown to trigger corresponding adjustments to prevent future failures. We reanalyzed existing datasets and conducted a novel experiment to investigate whether error-induced control states become bound to task-relevant stimuli. Results point towards a binding and retrieval of error-induced control states; however, the effect appears to be less reliable than for binding and retrieval of specific stimulus and response features. We discuss potential implications and alternative interpretations in terms of a mediating impact of error-induced control.

Feature-based attention interacts with emotional picture content during mid-latency and late ERP processing stages

Several components of the event-related potential (ERP) are amplified by emotional compared to neutral pictures. This study (N = 80) investigated systematically how attention to specific stimulus features influences ERPs to briefly presented (100 ms) negative and neutral pictures. Participants had to discriminate either (i) the orientation of overlaid lines, (ii) if the picture content was animate or inanimate, or (iii) if the emotional content was negative or neutral. ERP results showed interactions between the attention task and emotion processing for the early posterior negativity (EPN) and the late positive potential (LPP). For the EPN, attention to distracting perceptual information reduced emotional differences, while at the level of the LPP, emotion effects were selectively amplified when participants attended to the emotional content. These findings reveal the time-dependent effects of feature-based attention tasks on ERPs to emotional pictures.

Enhancing the dark side: asymmetric gain of cone photoreceptors underpins their discrimination of visual scenes based on skewness.

Psychophysical data indicate that humans can discriminate visual scenes based on their skewness, i.e. the ratio of dark and bright patches within a visual scene. It has also been shown that at a phenomenological level this skew discrimination is described by the so‐called blackshot mechanism, which accentuates strong negative contrasts within a scene. Here, we present a set of observations suggesting that the underlying computation might start as early as the cone phototransduction cascade, whose gain is higher for strong negative contrasts than for strong positive contrasts. We recorded from goldfish cone photoreceptors and found that the asymmetry in the phototransduction gain leads to responses with larger amplitudes when using negatively rather than positively skewed light stimuli. This asymmetry in amplitude was present in the cone photocurrent, voltage response and synaptic output. Given that the properties of the phototransduction cascade are universal across vertebrates, it is possible that the mechanism shown here gives rise to a general ability to discriminate between scenes based only on their skewness, which psychophysical studies have shown humans can do. Thus, our data suggest the importance of non‐linearity of the early photoreceptor for perception. Additionally, we found that stimulus skewness leads to a subtle change in photoreceptor kinetics. For negatively skewed stimuli, the impulse response functions of the cone peak later than for positively skewed stimuli. However, stimulus skewness does not affect the overall integration time of the cone.Key points Humans can discriminate visual scenes based on skewness, i.e. the relative prevalence of bright and dark patches within a scene.Here, we show that negatively skewed time‐series stimuli induce larger responses in goldfish cone photoreceptors than comparable positively skewed stimuli.This response asymmetry originates from within the phototransduction cascade, where gain is higher for strong negative contrasts (dark patches) than for strong positive contrasts (bright patches).Unlike the implicit assumption often contained within models of downstream visual neurons, our data show that cone photoreceptors do not simply relay linearly filtered versions of visual stimuli to downstream circuitry, but that they also emphasize specific stimulus features.Given that the phototransduction cascade properties among vertebrate retinas are mostly universal, our data imply that the skew discrimination by human subjects reported in psychophysical studies might stem from the asymmetric gain function of the phototransduction cascade.

Synthesis of a comprehensive population code for contextual features in the awake sensory cortex.

How cortical circuits build representations of complex objects is poorly understood. Individual neurons must integrate broadly over space, yet simultaneously obtain sharp tuning to specific global stimulus features. Groups of neurons identifying different global features must then assemble into a population that forms a comprehensive code for these global stimulus properties. Although the logic for how single neurons summate over their spatial inputs has been well explored in anesthetized animals, how large groups of neurons compose a flexible population code of higher-order features in awake animals is not known. To address this question, we probed the integration and population coding of higher-order stimuli in the somatosensory and visual cortices of awake mice using two-photon calcium imaging across cortical layers. We developed a novel tactile stimulator that allowed the precise measurement of spatial summation even in actively whisking mice. Using this system, we found a sparse but comprehensive population code for higher-order tactile features that depends on a heterogeneous and neuron-specific logic of spatial summation beyond the receptive field. Different somatosensory cortical neurons summed specific combinations of sensory inputs supra-linearly, but integrated other inputs sub-linearly, leading to selective responses to higher-order features. Visual cortical populations employed a nearly identical scheme to generate a comprehensive population code for contextual stimuli. These results suggest that a heterogeneous logic of input-specific supra-linear summation may represent a widespread cortical mechanism for the synthesis of sparse higher-order feature codes in neural populations. This may explain how the brain exploits the thalamocortical expansion of dimensionality to encode arbitrary complex features of sensory stimuli.

Neural mechanisms of pain relief through paying attention to painful stimuli.

A commonly held belief suggests that turning one's attention away from pain reduces it, whereas paying attention to pain increases it. However, some attention-based therapeutic strategies for pain, such as mindfulness-based interventions, suggest that paying attention to painful stimuli can reduce pain, resulting in seemingly contradictory conclusions regarding attention and pain. Here, we investigated the analgesic effects of attention modulation and provide behavioral and neural evidence that paying attention to pain can reduce pain when attention is directed toward the specific features of painful stimuli. The analgesic effects of paying attention to painful stimuli were mediated by the primary somatosensory cortex and goal-directed attention regions in the prefrontal and parietal cortex. These findings suggest that suppressing early somatosensory processing through top-down modulation is the key mechanism of the analgesic effects of paying attention to painful stimuli, providing evidence that pain itself can be used as a component of pain management.

Identification of Pattern Completion Neurons in Neuronal Ensembles Using Probabilistic Graphical Models.

Neuronal ensembles are groups of neurons with coordinated activity that could represent sensory, motor, or cognitive states. The study of how neuronal ensembles are built, recalled, and involved in the guiding of complex behaviors has been limited by the lack of experimental and analytical tools to reliably identify and manipulate neurons that have the ability to activate entire ensembles. Such pattern completion neurons have also been proposed as key elements of artificial and biological neural networks. Indeed, the relevance of pattern completion neurons is highlighted by growing evidence that targeting them can activate neuronal ensembles and trigger behavior. As a method to reliably detect pattern completion neurons, we use conditional random fields (CRFs), a type of probabilistic graphical model. We apply CRFs to identify pattern completion neurons in ensembles in experiments using in vivo two-photon calcium imaging from primary visual cortex of male mice and confirm the CRFs predictions with two-photon optogenetics. To test the broader applicability of CRFs we also analyze publicly available calcium imaging data (Allen Institute Brain Observatory dataset) and demonstrate that CRFs can reliably identify neurons that predict specific features of visual stimuli. Finally, to explore the scalability of CRFs we apply them to in silico network simulations and show that CRFs-identified pattern completion neurons have increased functional connectivity. These results demonstrate the potential of CRFs to characterize and selectively manipulate neural circuits.SIGNIFICANCE STATEMENT We describe a graph theory method to identify and optically manipulate neurons with pattern completion capability in mouse cortical circuits. Using calcium imaging and two-photon optogenetics in vivo we confirm that key neurons identified by this method can recall entire neuronal ensembles. This method could be broadly applied to manipulate neuronal ensemble activity to trigger behavior or for therapeutic applications in brain prostheses.

Visual intracortical and transthalamic pathways carry distinct information to cortical areas

SummarySensory processing involves information flow between neocortical areas, assumed to rely on direct intracortical projections. However, cortical areas may also communicate indirectly via higher-order nuclei in the thalamus, such as the pulvinar or lateral posterior nucleus (LP) in the visual system of rodents. The fine-scale organization and function of these cortico-thalamo-cortical pathways remains unclear. We find that responses of mouse LP neurons projecting to higher visual areas likely derive from feedforward input from primary visual cortex (V1) combined with information from many cortical and subcortical areas, including superior colliculus. Signals from LP projections to different higher visual areas are tuned to specific features of visual stimuli and their locomotor context, distinct from the signals carried by direct intracortical projections from V1. Thus, visual transthalamic pathways are functionally specific to their cortical target, different from feedforward cortical pathways, and combine information from multiple brain regions, linking sensory signals with behavioral context.

Audiovisual looming signals are not always prioritised: evidence from exogenous, endogenous and sustained attention

ABSTRACT The majority of studies showing multisensory attention benefits have focused on brief audiovisual events. Here we examined whether attention benefits can occur for auditory and visual signals that change in synchrony over time. In the first two experiments, we found no evidence that attention was captured more by synchronous compared to asynchronous audiovisual and visual looming signals. The results of our third experiment suggested that attention was not preferentially oriented towards synchronous compared to asynchronous audiovisual and visual looming signals. In the fourth experiment, we found no evidence for better sustained attention for synchronous compared to asynchronous audiovisual looming and unisensory signals. Together, these findings indicate that synchronous multisensory looming signals are not always prioritised by our information processing system. Future multisensory research should focus on more conceptual clarity and deepen our understanding of the specific stimulus, task and contextual features affecting the strength and quality of multisensory integration.

Unique Neural Activity Patterns Among Lower Order Cortices and Shared Patterns Among Higher Order Cortices During Processing of Similar Shapes With Different Stimulus Types.

We investigated the neural mechanism of the processing of three-dimensional (3D) shapes defined by disparity and perspective. We measured blood oxygenation level-dependent signals as participants viewed and classified 3D images of convex–concave shapes. According to the cue (disparity or perspective) and element type (random dots or black and white dotted lines), three types of stimuli were used: random dot stereogram, black and white dotted lines with perspective, and black and white dotted lines with binocular disparity. The blood oxygenation level-dependent images were then classified by multivoxel pattern analysis. To identify areas selective to shape, we assessed convex–concave classification accuracy with classifiers trained and tested using signals evoked by the same stimulus type (same cue and element type). To identify cortical regions with similar neural activity patterns regardless of stimulus type, we assessed the convex–concave classification accuracy of transfer classification in which classifiers were trained and tested using different stimulus types (different cues or element types). Classification accuracy using the same stimulus type was high in the early visual areas and subregions of the intraparietal sulcus (IPS), whereas transfer classification accuracy was high in the dorsal subregions of the IPS. These results indicate that the early visual areas process the specific features of stimuli, whereas the IPS regions perform more generalized processing of 3D shapes, independent of a specific stimulus type.

Combining fMRI and Eye-tracking for the Study of Social Cognition.

The study of social cognition with functional magnetic resonance imaging (fMRI) affords the use of complex stimulus material. Visual attention to distinct aspects of these stimuli can result in the involvement of remarkably different neural systems. Usually, the influence of gaze on neural signal is either disregarded or dealt with by controlling gaze of participants through instructions or tasks. However, behavioral restrictions like this limit the study’s ecological validity. Thus, it would be preferable if participants freely look at the stimuli while their gaze traces are measured. Yet several impediments hamper a combination of fMRI and eye-tracking. In our recent work on neural Theory of Mind processes in alexithymia, we propose a simple way of integrating dwell time on specific stimulus features into general linear models of fMRI data. By parametrically modeling fixations, we were able to distinguish neural processes asssociated with specific stimulus features looked at. Here, I discuss opportunities and obstacles of this approach in more detail. My goal is to motivate a wider use of parametric models — usually implemented in common fMRI software packages — to combine fMRI and eye-tracking data.

A Sensorimotor Numerosity System.

Incoming sensory input provides information for the planning and execution of actions, which yield motor outcomes that are themselves sensory inputs. One dimension where action and perception strongly interact is numerosity perception. Many non-human animals can estimate approximately the number of external elements as well as their own actions, and neurons have been identified that respond to both. Recent psychophysical adaptation studies on humans also provide evidence for neural mechanisms responding to both the number of externally generated events and self-produced actions. Here we advance the idea that these strong connections may arise from dedicated sensorimotor mechanisms in the brain, part of a more generalized system interfacing action with the processing of other quantitative magnitudes such as space and time.

Left-Hemispheric Asymmetry for Object-Based Attention: an ERP Study.

It has been shown that selective attention enhances the activity in visual regions associated with stimulus processing. The left hemisphere seems to have a prominent role when non-spatial attention is directed towards specific stimulus features (e.g., color, spatial frequency). The present electrophysiological study investigated the time course and neural correlates of object-based attention, under the assumption of left-hemispheric asymmetry. Twenty-nine right-handed participants were presented with 3D graphic images representing the shapes of different object categories (wooden dummies, chairs, structures of cubes) which lacked detail. They were instructed to press a button in response to a target stimulus indicated at the beginning of each run. The perception of non-target stimuli elicited a larger anterior N2 component, which was likely associated with motor inhibition. Conversely, target selection resulted in an enhanced selection negativity (SN) response lateralized over the left occipito-temporal regions, followed by a larger centro-parietal P300 response. These potentials were interpreted as indexing attentional selection and categorization processes, respectively. The standardized weighted low-resolution electromagnetic tomography (swLORETA) source reconstruction showed the engagement of a fronto-temporo-limbic network underlying object-based visual attention. Overall, the SN scalp distribution and relative neural generators hinted at a left-hemispheric advantage for non-spatial object-based visual attention.

Using intersection information to map stimulus information transfer within neural networks

Analytical tools that estimate the directed information flow between simultaneously recorded neural populations, such as directed information or Granger causality, typically focus on measuring how much information is exchanged between such populations. However, understanding how sensory information is processed through the brain and how it is used to generate behaviors requires estimating specifically the amount of stimulus information that is transmitted. Here we use the concept of intersection information to make progress on how to perform this measure. We develop the concept of transmitted intersection information, which measures how much of the stimulus information present in one population at a certain time is transmitted to a second population at a later time. We show that this measure of stimulus-specific information transfer has several appealing properties, such as being non-negative, and being bounded by the amount of stimulus information present in each of the two populations and by the total amount of information transmitted between the two populations. Applying this measure to simulated neurons or pools of neurons connected by feed-forward synapses, we show that it can discern cases when the information transmitted from one population to another is about specific stimulus features encoded by the sending population from cases in which the information transmitted is not about the stimuli. We also show that this measure has a good statistical sensitivity from trial numbers that can be collected in real data. Our results highlight the promise of using the concept of intersection information to map stimulus-specific information transfer across neural populations.

Evidence for intact stimulus-specific neural adaptation for visual objects in schizophrenia and bipolar disorder: An ERP study.

People with schizophrenia (SZ) or bipolar disorder (BD) experience dysfunction in visual processing. Dysfunctional neural tuning, in which neurons and neuronal populations are selectively activated by specific features of visual stimuli, may contribute to these deficits. Few studies have examined this possibility and there are inconsistent findings of tuning deficits in the literature. We utilized an event-related potential (ERP) paradigm to examine neural adaptation for visual objects, a measure of neural tuning whereby neurons respond less strongly to the repeated presentation of the same stimulus. Seventy-seven SZ, 53 BD, and 49 healthy comparison participants (HC) were examined. In three separate conditions, pictures of objects were presented repeatedly: the same object (SS), different objects from the same category (e.g., two different vases; SD), or different objects from different categories (e.g., a barrel and a clock, DD). Mass-univariate cluster-based permutation analyses identified electrodes and time-windows in which there were significant differences between the SS vs. DD and the SD vs. DD conditions. Mean ERP amplitudes were extracted from these clusters and analyzed for group differences. Results revealed a significant condition difference over parieto-occipital electrodes for the SS-DD comparison between 109–164 ms and for the SD-DD comparison between 78–203 ms, with larger amplitudes in the DD compared to either SS or SD condition. However, there were no significant differences in the pattern of results between groups. Thus, while we found neural adaptation effects using this ERP paradigm, we did not find evidence of group differences. Our results suggest that people with SZ or BD may not exhibit deficits in neural tuning for processing of visual objects using this EEG task with rapidly presented stimuli. However, the results are inconsistent with other studies using different methodologies (e.g., fMRI, behavioral tasks) that have found tuning deficits in people with schizophrenia.