Instant Effects of Semantic Information on Visual Perception.

Does our perception of an object change once we discover what function it serves? We showed human participants (n = 48, 31 females and 17 males) pictures of unfamiliar objects either together with keywords matching their function, leading to semantically informed perception, or together with nonmatching keywords, resulting in uninformed perception. We measured event-related potentials to investigate at which stages in the visual processing hierarchy these two types of object perception differed from one another. We found that semantically informed compared with uninformed perception was associated with larger amplitudes in the N170 component (150-200 ms), reduced amplitudes in the N400 component (400-700 ms), and a late decrease in alpha/beta band power. When the same objects were presented once more without any information, the N400 and event-related power effects persisted, and we also observed enlarged amplitudes in the P1 component (100-150 ms) in response to objects for which semantically informed perception had taken place. Consistent with previous work, this suggests that obtaining semantic information about previously unfamiliar objects alters aspects of their lower-level visual perception (P1 component), higher-level visual perception (N170 component), and semantic processing (N400 component, event-related power). Our study is the first to show that such effects occur instantly after semantic information has been provided for the first time, without requiring extensive learning.SIGNIFICANCE STATEMENT There has been a long-standing debate about whether or not higher-level cognitive capacities, such as semantic knowledge, can influence lower-level perceptual processing in a top-down fashion. Here we could show, for the first time, that information about the function of previously unfamiliar objects immediately influences cortical processing within less than 200 ms. Of note, this influence does not require training or experience with the objects and related semantic information. Therefore, our study is the first to show effects of cognition on perception while ruling out the possibility that prior knowledge merely acts by preactivating or altering stored visual representations. Instead, this knowledge seems to alter perception online, thus providing a compelling case against the impenetrability of perception by cognition.

Self-Assembled Hydrogel Membranes with Structurally Tunable Mechanical and Biological Properties.

Using supramolecular self-assembled nanocomposite materials made from protein and polysaccharide components is becoming more popular because of their unique properties, such as biodegradability, hierarchical structures, and tunable multifunctionality. However, the fabrication of these materials in a reproducible way remains a challenge. This study presents a new evaporation-induced self-assembly method producing layered hydrogel membranes (LHMs) using tropocollagen grafted by partially deacetylated chitin nanocrystals (CO-g-ChNCs). ChNCs help stabilize tropocollagen's helical conformation and fibrillar structure by forming a hierarchical microstructure through chemical and physical interactions. The LHMs show improved mechanical properties, cytocompatibility, and the ability to control drug release using octenidine dihydrochloride (OCT) as a drug model. Because of the high synergetic performance between CO and ChNCs, the modulus, strength, and toughness increased significantly compared to native CO. The biocompatibility of LHM was tested using the normal human dermal fibroblast (NHDF) and the human osteosarcoma cell line (Saos-2). Cytocompatibility and cell adhesion improved with the introduction of ChNCs. The extracted ChNCs are used as a reinforcing nanofiller to enhance the performance properties of tropocollagen hydrogel membranes and provide new insights into the design of novel LHMs that could be used for various medical applications, such as control of drug release in the skin and bone tissue regeneration.

Distrust before first sight? Examining knowledge- and appearance-based effects of trustworthiness on the visual consciousness of faces.

The present EEG study with 32 healthy participants investigated whether affective knowledge about a person influences the visual awareness of their face, additionally considering the impact of facial appearance. Faces differing in perceived trustworthiness based on appearance were associated with negative or neutral social information and shown as target stimuli in an attentional blink task. As expected, participants showed enhanced awareness of faces associated with negative compared to neutral social information. On the neurophysiological level, this effect was connected to differences in the time range of the early posterior negativity (EPN)-a component associated with enhanced attention and facilitated processing of emotional stimuli. The findings indicate that the social-affective relevance of a face based on emotional knowledge is accessed during a phase of attentional enhancement for conscious perception and can affect prioritization for awareness. In contrast, no clear evidence for influences of facial trustworthiness during the attentional blink was found.

Electrophysiological Chronometry of Graded Consciousness during the Attentional Blink.

One of the ongoing debates about visual consciousness is whether it can be considered as an all-or-none or a graded phenomenon. While there is increasing evidence for the existence of graded states of conscious awareness based on paradigms such as visual masking, only little and mixed evidence is available for the attentional blink paradigm, specifically in regard to electrophysiological measures. Thereby, the all-or-none pattern reported in some attentional blink studies might have originated from specifics of the experimental design, suggesting the need to examine the generalizability of results. In the present event-related potential (ERP) study (N = 32), visual awareness of T2 face targets was assessed via subjective visibility ratings on a perceptual awareness scale in combination with ERPs time-locked to T2 onset (components P1, N1, N2, and P3). Furthermore, a classification task preceding visibility ratings allowed to track task performance. The behavioral results indicate a graded rather than an all-or-none pattern of visual awareness. Corresponding graded differences in the N1, N2, and P3 components were observed for the comparison of visibility levels. These findings suggest that conscious perception during the attentional blink can occur in a graded fashion.

Marine Biomaterials: Hyaluronan.

The marine-derived hyaluronic acid and other natural biopolymers offer exciting possibilities in the field of biomaterials, providing sustainable and biocompatible alternatives to synthetic materials. Their unique properties and abundance in marine sources make them valuable resources for various biomedical and industrial applications. Due to high biocompatible features and participation in biological processes related to tissue healing, hyaluronic acid has become widely used in tissue engineering applications, especially in the wound healing process. The present review enlightens marine hyaluronan biomaterial providing its sources, extraction process, structures, chemical modifications, biological properties, and biocidal applications, especially for wound healing/dressing purposes. Meanwhile, we point out the future development of wound healing/dressing based on hyaluronan and its composites and potential challenges.

Web-based language production experiments: Semantic interference assessment is robust for spoken and typed response modalities.

For experimental research on language production, temporal precision and high quality of the recorded audio files are imperative. These requirements are a considerable challenge if language production is to be investigated online. However, online research has huge potential in terms of efficiency, ecological validity and diversity of study populations in psycholinguistic and related research, also beyond the current situation. Here, we supply confirmatory evidence that language production can be investigated online and that reaction time (RT) distributions and error rates are similar in written naming responses (using the keyboard) and typical overt spoken responses. To assess semantic interference effects in both modalities, we performed two pre-registered experiments (n = 30 each) in online settings using the participants' web browsers. A cumulative semantic interference (CSI) paradigm was employed that required naming several exemplars of semantic categories within a seemingly unrelated sequence of objects. RT is expected to increase linearly for each additional exemplar of a category. In Experiment 1, CSI effects in naming times described in lab-based studies were replicated. In Experiment 2, the responses were typed on participants' computer keyboards, and the first correct key press was used for RT analysis. This novel response assessment yielded a qualitatively similar, very robust CSI effect. Besides technical ease of application, collecting typewritten responses and automatic data preprocessing substantially reduce the work load for language production research. Results of both experiments open new perspectives for research on RT effects in language experiments across a wide range of contexts. JavaScript- and R-based implementations for data collection and processing are available for download.

Knowledge-augmented face perception: Prospects for the Bayesian brain-framework to align AI and human vision.

Human visual perception is efficient, flexible and context-sensitive. The Bayesian brain view explains this with probabilistic perceptual inference integrating prior experience and knowledge through top-down influences. Advances in machine learning, such as Artificial Neural Networks (ANNs), have enabled considerable progress in computer vision. Unlike humans, these networks do not yet adaptively draw on meaningful and task-relevant contextual cues and prior knowledge. We propose ideas to better align human and computer vision, applied to facial expression recognition. We review evidence of knowledge-augmented and context-sensitive face perception in humans and approaches trying to leverage such sources of information in computer vision. We discuss how both fields can establish an epistemic loop: Redesigning synthetic systems with inspiration from the Bayesian brain-framework could make networks more flexible and useful for human-machine interaction. In turn, employing ANNs as scientific tools will widen the scope of empirical research into human knowledge-augmented perception.

Semantic Interference through Multiple Distractors in Picture Naming in People with Aphasia.

When we refer to an object or concept by its name, activation of semantic and categorical information is necessary to retrieve the correct lexical representation. Whereas in neurotypical individuals it is well established that semantic context can interfere with or facilitate lexical retrieval, these effects are much less studied in people with lesions to the language network and impairment at different steps of lexical-semantic processing. Here, we applied a novel picture naming paradigm, where multiple categorically related and unrelated words were presented as distractors before a to-be-named target picture. Using eye tracking, we investigated preferential fixation on the cohort members versus nonmembers. Thereby, we can judge the impact of explicit acknowledgment of the category and its effect on semantic interference. We found that, in contrast to neurotypical participants [van Scherpenberg, C., Abdel Rahman, R., & Obrig, H. A novel multiword paradigm for investigating semantic context effects in language production. PLoS One, 15, e0230439, 2020], participants suffering from mild to moderate aphasia did not show a fixation preference on category members but still showed a large interference effect of ∼35 msec, confirming the implicit mechanism of categorical interference. However, preferential fixation on the categorically related cohort words correlated with clinical tests regarding nonverbal semantic abilities and integrity of the anterior temporal lobe. This highlights the role of supramodal semantics for explicit recognition of a semantic category, while semantic interference is triggered if the threshold of lexical cohort activation is reached. Confirming psycholinguistic evidence, the demonstration of a large and persistent interference effect through implicit lexico-semantic activation is important to understand deficits in people with a lesion in thelanguage network, potentially relevant for individualized intervention aiming at improving naming skills.

Negative news dominates fast and slow brain responses and social judgments even after source credibility evaluation.

Remedies to counter the impact of misinformation are in high demand, but little is known about the neuro-cognitive consequences of untrustworthy information and how they can be mitigated. In this preregistered study, we investigated the effects of social-emotional headline contents on social judgments and brain responses and whether they can be modulated by explicit evaluations of the trustworthiness of the media source. Participants (N = 30) evaluated -and clearly discerned- the trustworthiness of news sources before they were exposed to person-related news headlines. Despite this intervention, social judgments and brain responses were dominated largely by emotional headline contents. Results suggest differential effects of source credibility might depend on headline valence. Electrophysiological indexes of fast emotional and arousal-related brain responses, as well as correlates of slow evaluative processing were enhanced for persons associated with positive headline contents from trusted sources, but not when positive headlines stemmed from distrusted sources. In contrast, negative headlines dominated fast and slow brain responses unaffected by explicit source credibility evaluations. These results provide novel insights into the brain mechanisms underlying the "success" of emotional news from untrustworthy sources, suggesting a pronounced susceptibility to negative information even from distrusted sources that is reduced for positive contents. The differential pattern of responses to misinformation in mind and brain sheds light on the cognitive mechanisms underlying the processing of misinformation and possible strategies to avoid their potentially detrimental effects.

A meta-analysis of fMRI studies of semantic cognition in children.

Our capacity to derive meaning from things that we see and words that we hear is unparalleled in other animal species and current AI systems. Despite a wealth of functional magnetic resonance imaging (fMRI) studies on where different semantic features are processed in the adult brain, the development of these systems in children is poorly understood. Here we conducted an extensive database search and identified 50 fMRI experiments investigating semantic world knowledge, semantic relatedness judgments, and the differentiation of visual semantic object categories in children (total N = 1,018, mean age = 10.1 years, range 4-15 years). Synthesizing the results of these experiments, we found consistent activation in the bilateral inferior frontal gyri (IFG), fusiform gyri (FG), and supplementary motor areas (SMA), as well as in the left middle and superior temporal gyri (MTG/STG). Within this system, we found little evidence for age-related changes across childhood and high overlap with the adult semantic system. In sum, the identification of these cortical areas provides the starting point for further research on the mechanisms by which the developing brain learns to make sense of its environment.

Visual consciousness of faces in the attentional blink: Knowledge-based effects of trustworthiness dominate over appearance-based impressions.

How we perceive and evaluate other persons depends on appearance-based impressions as well as top-down information such as knowledge about someone's character. To date, little is known about how these two sources of information affect the conscious perception of faces, about their relative contributions and possible interactions. Here, we directly compare how social-affective knowledge and visual cues of trustworthiness impact the access of faces to visual consciousness. Low- and average-trustworthy looking faces were associated with neutral or negative information about a person's social behavior. Trustworthiness and facial expression ratings showed robust and independent effects of both sources of information during evaluations. Under conditions of reduced attention in an attentional blink task, prioritized detection of faces associated with negative as compared to neutral person knowledge was observed, whereas facial trustworthiness did not affect detection. Thus, while both factors influenced conscious perception and evaluation, only person knowledge impacted the access to consciousness.

Semantic Knowledge Enhances Conscious Awareness of Visual Objects.

It is becoming increasingly established that information from long-term memory can influence early perceptual processing, a finding that is in line with recent theoretical approaches to cognition such as the predictive coding framework. Notwithstanding, the impact of semantic knowledge on conscious perception and the temporal dynamics of such an influence remain unclear. To address this question, we presented pictures of novel objects to participants as the second of two targets in an attentional blink paradigm. We found that associating newly acquired semantic knowledge to objects increased overall conscious detection in comparison to objects associated with minimal knowledge while controlling for object familiarity. Additionally, event-related brain potentials revealed a corresponding modulation beginning 100 msec after stimulus presentation in the P1 component. Furthermore, the size of this modulation was correlated with participant's subjective reports of conscious perception. These findings suggest that semantic knowledge can shape the contents of consciousness by affecting early stages of perceptual processing.

No matter how: Top-down effects of verbal and semantic category knowledge on early visual perception.

Language is assumed to augment human cognition. But can language also affect basic mechanisms of perception, suggesting cognitive penetrability of perception? This idea is highly controversial: linguistic categorization may induce top-down effects on ongoing perceptual processing. Alternatively, such effects may not concern perception proper, but pre-perceptual shifts of attention or downstream processes, such as perceptual judgment. This study provides a critical test of these views by investigating categorical perception (CP) of novel objects in a balanced learning design, controlling for perceptual experience and low-level visual differences. To better understand which linguistic representations induce CP, we manipulated the type of information categories were based on: bare verbal labels, in-depth semantic knowledge, or the combined information from labels associated with semantic knowledge. We used event-related brain potentials (ERPs) derived from the EEG in a visual search task to localize CP effects at perceptual or pre/post-perceptual stages. The results replicated behavioral CP with facilitated visual search when target and distractors belonged to different linguistic categories. ERPs revealed CP effects in the P1 and N1 components, associated with early visual processing. Attentional selection, reflected in the N2, also was influenced by linguistic categories. The N2 and the N400, a measure of high-level semantic processing, were sensitive to the depth of semantic knowledge associated with objects. CP, however, did not differ between category types, suggesting that any linguistic categorization can lead to CP. The findings support cognitive penetrability of perception, with linguistic categories informing perceptual predictions down to the processing of low-level visual features.

A close call: Interference from semantic neighbourhood density and similarity in language production.

The present study investigated how lexical selection is influenced by the number of semantically related representations (semantic neighbourhood density) and their similarity (semantic distance) to the target in a speeded picture-naming task. Semantic neighbourhood density and similarity as continuous variables were used to assess lexical selection for which competitive and noncompetitive mechanisms have been proposed. Previous studies found mixed effects of semantic neighbourhood variables, leaving this issue unresolved. Here, we demonstrate interference of semantic neighbourhood similarity with less accurate naming responses and a higher likelihood of producing semantic errors and omissions over accurate responses for words with semantically more similar (closer) neighbours. No main effect of semantic neighbourhood density and no interaction between semantic neighbourhood density and similarity was found. We assessed further whether semantic neighbourhood density can affect naming performance if semantic neighbours exceed a certain degree of semantic similarity. Semantic similarity between the target and each neighbour was used to split semantic neighbourhood density into two different density variables: The number of semantically close neighbours versus distant neighbours. The results showed a significant effect of close, but not of distant, semantic neighbourhood density: Naming pictures of targets with more close semantic neighbours led to longer naming latencies, less accurate responses, and a higher likelihood for the production of semantic errors and omissions over accurate responses. The results show that word inherent semantic attributes such as semantic neighbourhood similarity and the number of coactivated close semantic neighbours modulate lexical selection supporting theories of competitive lexical processing.

Native Language Promotes Access to Visual Consciousness.

Can our native language influence what we consciously perceive? Although evidence that language modulates visual discrimination has been accumulating, little is known about the relation between language structure and consciousness. We employed electroencephalography and the attentional-blink paradigm, in which targets are often unnoticed. Native Greek speakers ( N = 28), who distinguish categorically between light and dark shades of blue, showed boosted perception for this contrast compared with a verbally unmarked green contrast. Electrophysiological signatures of early visual processing predicted this behavioral advantage. German speakers ( N = 29), who have only one category for light and dark shades of blue, showed no differences in perception between blue and green targets. The behavioral consequence of categorical perception was replicated with Russian speakers ( N = 46), reproducing this novel finding. We conclude that linguistic enhancement of color contrasts provides targets with a head start in accessing visual consciousness. Our native language is thus one of the forces that determine what we consciously perceive.

Articulation Artifacts During Overt Language Production in Event-Related Brain Potentials: Description and Correction.

Overt articulation produces strong artifacts in the electroencephalogram and in event-related potentials (ERPs), posing a serious problem for investigating language production with these variables. Here we describe the properties of articulation-related artifacts and propose a novel correction procedure. Experiment 1 co-recorded ERPs and trajectories of the articulators with an electromagnetic articulograph from a single participant. The generalization of the findings from the single participant to standard picture naming was investigated in Experiment 2. Both experiments provided evidence that articulation-induced artifacts may start up to 300 ms or more prior to voice onset or voice key onset-depending on the specific measure; they are highly similar in topography across many different phoneme patterns and differ mainly in their time course and amplitude. ERPs were separated from articulation-related artifacts with residue iteration decomposition (RIDE). After obtaining the artifact-free ERPs, their correlations with the articulatory trajectories dropped near to zero. Artifact removal with independent component analysis was less successful; while correlations with the articulatory movements remained substantial, early components prior to voice onset were attenuated in reconstructed ERPs. These findings offer new insights into the nature of articulation artifacts; together with RIDE as method for artifact removal the present report offers a fresh perspective for ERP studies requiring overt articulation.

Mental imagery of emotions: Electrophysiological evidence.

Affective stimuli such as emotional words, scenes or facial expressions elicit well-investigated emotional responses. For instance, two distinct event-related brain potentials (ERPs) have been reported in response to emotional facial expressions, the early posterior negativity (EPN), associated with enhanced attention and perception of affective stimuli, and a later centro-parietal positivity (LPP) that is taken to reflect evaluations of the intrinsic relevance of emotional stimuli. However, other rich sources of emotions that have as yet received little attention are internal mental events such as thoughts, memories and imagination. Here we investigated mental imagery of emotional facial expressions and its time course using ERPs. Participants viewed neutral familiar and unfamiliar faces, and were subsequently asked to imagine the faces with an emotional or neutral expression. Imagery was compared to visually perceiving the same faces with the different expressions. Early ERP modulations during imagery resemble the effects frequently reported for perceived emotional facial expressions, suggesting that common early processes are associated with emotion perception and imagination. A later posterior positivity was also found in the imagery condition, but with a different distribution than for perception. These findings underscore the similarity of the brain's responses to internally generated and external sources of emotions.

Affective responses to emotional words are boosted in communicative situations.

Emotional verbal messages are typically encountered in meaningful contexts, for instance, during face-to-face communication in social situations. Yet, they are often investigated by confronting single participants with isolated words on a computer screen, thus potentially lacking ecological validity. In the present study we recorded event-related brain potentials (ERPs) during emotional word processing in communicative situations provided by videos of a speaker, assuming that emotion effects should be augmented by the presence of a speaker addressing the listener. Indeed, compared to non-communicative situations or isolated word processing, emotion effects were more pronounced, started earlier and lasted longer in communicative situations. Furthermore, while the brain responded most strongly to negative words when presented in isolation, a positivity bias with more pronounced emotion effects for positive words was observed in communicative situations. These findings demonstrate that communicative situations--in which verbal emotions are typically encountered--strongly enhance emotion effects, underlining the importance of social and meaningful contexts in processing emotional and verbal messages.

Does the semantic content of verbal categories influence categorical perception? An ERP study.

Accumulating evidence suggests that visual perception and, in particular, visual discrimination, can be influenced by verbal category boundaries. One issue that still awaits systematic investigation is the specific influence of semantic contents of verbal categories on categorical perception (CP). We tackled this issue with a learning paradigm in which initially unfamiliar, yet realistic objects were associated with either bare labels lacking explicit semantic content or labels that were accompanied by enriched semantic information about the specific meaning of the label. Two to three days after learning, the EEG was recorded while participants performed a lateralized oddball task. Newly acquired verbal category boundaries modulated low-level aspects of visual perception as early as 100-150 ms after stimulus onset, suggesting a genuine influence of language on perception. Importantly, this effect was not further influenced by enriched semantic category information, suggesting that bare labels and the associated minimal and predominantly perceptual information are sufficient for CP. Distinct effects of semantic knowledge independent of category boundaries were found subsequently, starting at about 200 ms, possibly reflecting selective attention to semantically meaningful visual features.