Biology subjects

Abdel Rahman, R.

Publications and source records attributed to Abdel Rahman, R..

9 recordsLinked to original sources

bioRxiv2023

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 female, 17 male) pictures of unfamiliar objects either together with keywords matching their function, leading to semantically informed perception, or together with non-matching keywords, resulting in uninformed perception. We measured event-related potentials (ERPs) 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 as compared to 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 StatementThere 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 pre-activating 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.

neuroscience↗

bioRxiv2021

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.

neuroscience↗

bioRxiv2021

Distrust Before First Sight: 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.

neuroscience↗

bioRxiv2021

Graded Visual 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. This may depend on the experimental paradigm and the task used to investigate this question. The present event-related potential study (N = 32) focuses on the attentional blink paradigm for which so far only little and mixed evidence is available. Detection of T2 face targets during the attentional blink was assessed via an objective accuracy measure (reporting the faces gender), subjective visibility on a perceptual awareness scale (PAS) as well as event-related potentials time-locked to T2 onset (components P1, N1, N2, and P3). 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.

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bioRxiv2020

Joint language production: an electrophysiological investigation of simulated lexical access on behalf of task partner

This study investigates in a joint action setting a well-established effect in speech production, cumulative semantic interference, an increase in naming latencies when naming a series of semantically related pictures. In a joint action setting, two task partners take turns naming pictures. Previous work in this setting demonstrated that naming latencies increase not only with each semantically related picture speakers named themselves, but also with each picture named by the partner (Hoedemaker, Ernst, Meyer, & Belke, 2017; Kuhlen & Abdel Rahman, 2017). This suggests that speakers pursue lexical access on behalf of their partner. In two electrophysiological experiments (N=30 each) we investigated the neuro-cognitive signatures of such simulated lexical access. As expected, in both experiments speakers naming latency increased with successive naming instances within a given semantic category. Correspondingly, speakers EEG showed an increasing posterior positivity between 250-400ms, an ERP modulation typically associated with lexical access. However, unlike previous experiments, speakers were not influenced by their partners picture naming. Accordingly, we found no electrophysiological evidence of lexical access. To reconcile these findings we pooled behavioral data from five experiments (N=144). Within this large sample we find empirical evidence for partner-elicited interference. Furthermore, our data suggests that speakers may be less affected by their partners naming response in settings with remotely located task partners (as in present experiments). We conclude that speakers do not always represent their partners naming response and that our experimental setting may have limited the participants evaluation of the task as a joint action.

neuroscience↗

bioRxiv2020

Mental Chronometry of Speaking in Dialogue: Semantic Interference Turns into Facilitation

Numerous studies demonstrate that the production of words is delayed when speakers process in temporal proximity semantically related words. Yet the experimental settings underlying this effect are different from those under which we typically speak. This study demonstrates that semantic interference disappears, and can even turn into facilitation, when semantically related words are embedded in a meaningful communicative exchange. Experiment 1 and 3 (each N=32 university students) implemented a picture- word interference task in a game played between two participants: one named the distractor word and, after a stimulus-onset-asynchrony of -150ms or -650ms, the other named a semantically related or unrelated target picture. Semantic interference reappeared with identical experimental parameters in a single-person picture-word interference setting (Experiment 2, N=32). We conclude that the inhibitory context effects leading to semantic interference in single-subject settings are attenuated whereas facilitatory effects are enhanced in communicative settings. HighlightsO_LIIn isolated speakers processing semantically related words interferes with speaking C_LIO_LIYet we typically speak to communicate with others C_LIO_LIThis study transfers picture-word interference to a communicative setting C_LIO_LISemantically related words produced by a partner do not interfere with speaking C_LI

neuroscience↗

bioRxiv2020

Emotional news affects information processing and social judgments independent of perceived media credibility

How does the credibility we attribute to media sources influence our opinions and judgments derived from news? Participants read headlines about the social behavior of depicted unfamiliar persons from websites of trusted or distrusted well-known German news media. As a consequence, persons paired with negative or positive headlines were judged more negative or positive than persons associated with neutral information independent of source credibility. Likewise, electrophysiological signatures of slow and controlled evaluative brain activity revealed a dominant influence of emotional headline contents regardless of credibility. Modulations of earlier brain responses associated with arousal and reflexive emotional processing show an effect of negative news and suggest that distrusted sources may even enhance the impact of negative headlines. These findings demonstrate that even though we acknowledge source credibility, information processing and social judgments rely on the emotional content of headlines, even when they stem from sources we distrust.

neuroscience↗

bioRxiv2020

Time course and shared neurocognitive mechanisms of mental imagery and visual perception

When we imagine an object and when we actually see that object, similar brain regions become active. Yet, the time course and mechanisms with which imagery engages perceptual networks remain to be better understood. An emerging view holds that imagery and perception follow distinct dynamics during early visual processing with similarities arising only during later, high-level visual processing. However, confounds of visual stimulation and paradigms favoring observation of high-level processes associated with subjective imagery strength may have precluded evidence of earlier shared mechanisms. We therefore manipulated prior knowledge that informs early-stage top-down predictions and tracked electrophysiological brain responses while fully controlling visual stimulation. Participants saw and imagined objects associated with varying amounts of semantic knowledge. Imagery and perception were equally influenced by knowledge at an early stage (P1 component), revealing shared mechanisms that support low-level visual processing. This finding complements previous research by showing that imagery is not merely perception in reverse. Instead, in line with the predictive processing framework, both, perception and imagery are active and constructive processes that share top-down mechanisms already in early phases of processing.

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bioRxiv2018

Object naming is facilitated by semantic richness but inhibited by semantic density: Electrophysiological and behavioral evidence

Language production ultimately aims to convey meaning. Yet, words differ widely in the richness and density of their semantic representations and these differences impact conceptual and lexical processes during speech planning. Here, we replicate the recent finding that semantic richness, measured as the number of associated semantic features according to semantic feature production norms, facilitates object naming. In contrast, intercorrelational semantic feature density, measured as the degree of intercorrelation of a concepts features, presumably resulting in the coactivation of closely related concepts, has an inhibitory influence. We replicate the behavioral effects and investigate their relative time course and electrophysiological correlates. Both the facilitatory effect of high semantic richness and the inhibitory influence of high feature density were reflected in an increased posterior positivity starting at about 250 ms, in line with previous reports of posterior positivities in paradigms employing contextual manipulations to induce semantic interference during language production. Furthermore, amplitudes at the same posterior electrode sites were positively correlated with object naming times between about 230 and 380 ms. The observed effects follow naturally from the assumption of conceptual facilitation and simultaneous lexical competition, and are difficult to explain by language production theories dismissing lexical competition.

neuroscience↗