Biology subjects

Segaert, K.

Publications and source records attributed to Segaert, K..

At least 19 recordsLinked to original sources

bioRxiv2026

Older Adults Show Preserved Neural Signatures of Audiovisual Integration but Altered Links to Speech Comprehension

Older adults often experience difficulty understanding speech in noisy environments despite relatively preserved hearing. Although visual speech cues can improve speech perception, it remains unclear whether the neural mechanisms supporting audiovisual integration are preserved in healthy ageing. We addressed this question using magnetoencephalography (MEG) combined with Rapid Invisible Frequency Tagging (RIFT) during challenging audiovisual speech task. Forty younger and forty older adults attended to one of two competing speech streams while the speaker's lip movements were frequency tagged, with the visual modulation driven by either the attended or unattended speech envelope. Task-Relevant amplitude modulation of frequency tagging in visual speech improved speech comprehension in younger adults as previously reported for this cohort; this accuracy benefit was absent in older adults. Auditory and visual tagging responses were modulated by task relevance similarly across age groups, indicating largely preserved modality-specific sensory processing in older adults. Intermodulation responses, reflecting nonlinear interactions between auditory and visual speech signals, also remained sensitive to task relevance and did not differ in their condition-dependent modulation between age groups. Greater Task-Relevant versus Task-Irrelevant differences in intermodulation coherence were also associated with greater comprehension benefits in younger adults; no significant association was found in older adults, and this relationship differed significantly between age groups. These findings suggest that the absence of a comprehension benefit in older adults is linked to a change in the relationship between audiovisual intermodulation and behaviour, despite largely preserved task-sensitive brain responses.

neuroscience↗

bioRxiv2026

Augmenting Speech Comprehension using Rapid Frequency Tagging

Speech comprehension under adverse listening conditions benefits from visual speech, but whether visual input can be modulated to improve listening remains unclear. Here we used rapid frequency tagging, a non-invasive sensory stimulation technique, in which the visual tag at 55 Hz over the mouth region of a talking face was amplitude-modulated by the envelope of either the task-relevant or task-irrelevant speech stream. When the visual modulation followed the task-relevant speech envelope, comprehension improved relative to task-irrelevant modulation and to an unmodulated tagging control. MEG responses showed enhanced 55 Hz visual tagging, altered 40 Hz auditory tagging and a non-linear 15 Hz intermodulation. Individual comprehension gains were associated with intermodulation responses in left inferior frontal cortex, linking behavioural benefit to audiovisual interaction. These findings show that task-relevant visual stimulation can improve comprehension by strengthening audiovisual interaction, establishing amplitude-modulated frequency tagging as a tool for probing and supporting comprehension in challenging environments.

neuroscience↗

bioRxiv2023

Determinants of cerebral blood flow and arterial transit time in healthy older adults

Cerebral blood flow (CBF) and arterial transit time (ATT), markers of brain vascular health, worsen with age. The primary aim of this cross-sectional study was to identify modifiable determinants of CBF and ATT in healthy older adults (n=78, aged 60-81 yrs). Associations between cardiorespiratory fitness and CBF or ATT were of particular interest as the impact of cardiorespiratory fitness is not clear in existing literature. Secondly, this study assessed whether CBF or ATT relate to cognitive function in older adults. Results from multiple linear regressions found higher BMI was associated with lower global CBF ({beta}=-0.35, P=0.008) and a longer global ATT ({beta}=0.30, P=0.017), global ATT lengthened with increasing age ({beta}=0.43, P=0.004), and higher cardiorespiratory fitness was associated with longer ATT in parietal ({beta}=0.44, P=0.004) and occipital ({beta}=0.45, P=0.003) regions. Global or regional CBF or ATT were not associated with processing speed, working memory, or attention. In conclusion, preventing excessive weight gain may help attenuate age-related declines in brain vascular health. ATT may be more sensitive to age-related decline than CBF, and therefore useful for early detection and management of cerebrovascular impairment. Finally, cardiorespiratory fitness appears to have little effect on CBF but may induce longer ATT in specific regions.

physiology↗

bioRxiv2023

Lifestyle and brain health determinants of word-finding failures in healthy ageing

Cognitive decline associated with healthy ageing is multifactorial: brain-based and lifestyle factors uniquely and jointly contribute to distinct neurocognitive trajectories of ageing. To evaluate existing models of neurocognitive ageing such as compensation, maintenance, or reserve, we explore how various known brain-based and cardiorespiratory fitness factors intersect to better understand cognitive decline. In a pre-registered study (https://osf.io/6fqg7), we tested 73 healthy older adults aged 60--81 (M = 65.51, SD = 4.94) and collected neuroimaging (functional, structural, and perfusion MRI), cardiorespiratory fitness, and cognitive data to investigate a prominent challenge for older adults: word-finding failures. fMRI signal was recorded while participants responded to a definition-based tip-of-the-tongue task, T1-weighted imaging estimated grey matter volume, and cerebral blood flow was indexed using multi-delay pseudo-continuous arterial spin labelling. Commonality analyses were used to analyse these multi-domain data (neuroimaging, cardiorespiratory fitness, language skills, demographic characteristics) and uncover associations between predictors in explaining age-related tip-of-the-tongue rates. Commonality analyses revealed that functional activation of language networks associated with tip-of-the-tongue states is in part linked with age and, interestingly, cardiorespiratory fitness: the combination of higher cardiorespiratory fitness and functional recruitment in some older adults offsets part of the age-related variance in tip-of-the-tongues. Moreover, age-associated atrophy and perfusion in regions other than those showing functional differences accounted for variance in tip-of-the-tongues. Our findings can be interpreted in the context of the classic models of neurocognitive ageing, suggesting compensation. Brain health indices in concordance with cardiorespiratory fitness can provide a more holistic explanation of individual differences in age-related cognitive decline. HighlightsO_LIWord-finding problems are linked to brain health and cardiorespiratory fitness (CRF) C_LIO_LIBrain activity linked to word-finding failures is modulated by CRF and age C_LIO_LIDistinct contribution of structure and perfusion also associated with word-finding C_LIO_LILinking brain and CRF factors provides better account of age-related cognitive decline C_LI

neuroscience↗

bioRxiv2023

Brain-to-brain coupling forecasts future joint action outcomes

In this study, we investigated whether brain-to-brain coupling patterns could predict performance in a time-estimation task which requires two players to cooperate. The participant pairs, were tasked with synchronising button presses after converging on a shared representation of short, medium, and long time intervals while utilizing feedback to adjust responses. We employed EEG-hyperscanning and focused on post-feedback brain activity. We found that negative feedback led to increased frontal mid-line theta activity across individuals. Moreover, a correlation in post-feedback theta power between players forecasted failed joint action, while an anti-correlation forecasted success. These findings suggest that temporally coupled feedback related brain activity between two individuals serves as an indicator of redundancy in adjustment of a common goal representation. Additionally, the anti-correlation of this activity reflects cognitive strategic mechanisms that ensure optimal joint action outcomes. Rather than a paired overcompensation, successful cooperation requires flexible strategic agility from both partners.

neuroscience↗

bioRxiv2022

Functional neural architecture of cognitive control mediates the relationship between individual differences in bilingual experience and behaviour

Bilinguals have often, but not always, been found to outperform monolinguals on domain-general attentional control. Inconsistent findings have been argued to stem, at least partly, from treating bilingualism as a uniform category and from not considering how neural adaptations to bilingual experiences modulate behavioural outcomes. The present study investigated how patterns of language experience, including language switching behaviour, duration and intensity/diversity of bilingual language use, influence the brain processes underlying cognitive control, and how these in turn translate to cognitive control performance. We examined reaction times and spectral dynamics of the electroencephalograms (EEG) of two-hundred-and-thirty-nine participants (about 70% bilinguals) with diverse language experiences during two cognitive control paradigms testing interference suppression (flanker and Simon task). Using structural equation modelling, we found that different bilingual experience factors were related with neurocognitive measures, which in turn were related with behavioural interference effects, for the flanker but not the Simon task. More specifically, increased frequency of language switching and intensity / diversity of bilingual language usage was negatively related to induced top-down control measures (especially midline-frontal theta), which in turn was beneficial for interference control. In contrast, duration of bilingual engagement correlated negatively with evoked bottom-up control measures (especially P3) and was therefore detrimental to interference control. We demonstrate here for the first time how the different factors of bilingual experience lead to different neural adaptations which impact behavioural outcomes. Significance statementLike other intensive experiences, bilingualism leads to brain adaptations. It results in structural changes in language areas, and, due to demands on language control, in brain areas associated with domain-general cognitive control. Related to this, bilinguals often outperform monolinguals on cognitive control tasks. But what is often ignored is that bilingualism is a multi-dimensional phenomenon, with variations such as diversity of language usage and duration of language use. The present large-scale study of neural functioning in bilingualism revealed for the first time how individual differences in bilingual experience lead to adaptations to brain functioning which in turn affect cognitive control behaviour. It exemplifies how the complexity of individual experiences plays a fundamental role in brain function.

neuroscience↗

bioRxiv2021

Modulation in Alpha Band Activity Reflects Syntax Composition: An MEG Study of Minimal Syntactic Binding

Successful sentence comprehension requires the binding, or composition, of multiple words into larger structures to establish meaning. Using magnetoencephalography, we investigated the neural mechanisms involved in binding at the syntax level, in a task where contributions from semantics were minimized. Participants were auditorily presented with minimal sentences that required binding (pronoun and pseudo-verb with the corresponding morphological inflection; "she grushes") and pseudo-verb wordlists that did not require binding ("cugged grushes"). Relative to no binding, we found that syntactic binding was associated with a modulation in alpha band (8-12 Hz) activity in left-lateralized language regions. First, we observed a significantly smaller increase in alpha power around the presentation of the target word ("grushes") that required binding (-0.05s to 0.1s), which we suggest reflects an expectation of binding to occur. Second, during binding of the target word (0.15s to 0.25s), we observed significantly decreased alpha phase-locking between the left inferior frontal gyrus and the left middle/inferior temporal cortex, which we suggest reflects alpha-driven cortical disinhibition serving to strengthen communication within the syntax composition neural network. Together, our findings highlight the critical role of rapid spatial-temporal alpha band activity in controlling the allocation, transfer and coordination of the brains resources during syntax composition.

neuroscience↗

bioRxiv2021

Minimal phrase composition revealed by intracranial recordings

The ability to comprehend phrases is an essential integrative property of the brain. Here we evaluate the neural processes that enable the transition from single word processing to a minimal compositional scheme. Previous research has reported conflicting timing effects of composition, and disagreement persists with respect to inferior frontal and posterior temporal contributions. To address these issues, 19 patients (10 male, 19 female) implanted with penetrating depth or surface subdural intracranial electrodes heard auditory recordings of adjective-noun, pseudoword-noun and adjective-pseudoword phrases and judged whether the phrase matched a picture. Stimulus-dependent alterations in broadband gamma activity, low frequency power and phase-locking values across the language-dominant left hemisphere were derived. This revealed a mosaic located in the posterior superior temporal sulcus (pSTS), in which closely neighboring cortical sites displayed exclusive sensitivity to either lexicality or phrase structure, but not both. Distinct timings were found for effects of phrase composition (210-300 ms) and pseudoword processing (approximately 300-700 ms), and these were localized to neighboring electrodes in pSTS. The pars triangularis and temporal pole encode anticipation of composition in broadband low frequencies, and both regions exhibit greater functional connectivity with pSTS during phrase composition. Our results suggest that the pSTS is a highly specialized region comprised of sparsely interwoven heterogeneous constituents that encodes both lower and higher level linguistic features. This hub in pSTS for minimal phrase processing may form the neural basis for the human-specific computational capacity for forming hierarchically organized linguistic structures. SignificanceLinguists have claimed that the integration of multiple words into a phrase demands a computational procedure distinct from single word processing. Here, we provide intracranial recordings from a large patient cohort, with high spatiotemporal resolution, to track the cortical dynamics of phrase composition. Epileptic patients volunteered to participate in a task in which they listened to phrases ("red boat"), word-pseudoword or pseudoword-word pairs (e.g., "red fulg"). At the onset of the second word in phrases, greater broadband high gamma activity was found in posterior superior temporal sulcus in electrodes that exclusively indexed phrasal meaning, and not lexical meaning. These results provide direct, high-resolution signatures of minimal phrase composition in humans, a potentially species-specific computational capacity.

neuroscience↗

bioRxiv2021

How the healthy ageing brain supports semantic binding during language comprehension

Semantic binding refers to constructing complex meaning based on elementary building blocks. Using EEG, we investigated the age-related changes in modulations of oscillatory brain activity supporting lexical retrieval and semantic binding. Young and older adult participants were visually presented two-word phrases, which for the first word revealed a lexical retrieval signature (e.g. swift vs. swrfeq) and for the second word revealed a semantic binding signature (e.g. horse in a semantic binding "swift horse" vs. no binding "swrfeq horse" context). The oscillatory brain activity associated with lexical retrieval as well as semantic binding significantly differed between healthy older and young adults. Specifically for lexical retrieval, we found that different age groups exhibited opposite patterns of theta and alpha modulation, which as a combined picture suggest that lexical retrieval is associated with different and delayed signatures in older compared to young adults. For semantic binding, in young adults we found a signature in the low-beta range centred around the target word onset (i.e. a smaller low-beta increase for binding relative to no binding), while in healthy older adults we found an opposite binding signature about ~500ms later in the low- and high-beta range (i.e. a smaller low- and high-beta decrease for binding relative to no binding). The novel finding of a different and delayed oscillatory signature for semantic binding in healthy older adults reflects that the integration of word meaning into the semantic context takes longer and relies on different mechanisms in healthy older compared to young adults.

neuroscience↗

bioRxiv2019

Laminar Specific fMRI Reveals Directed Interactions in Distributed Networks During Language Processing

Laminar resolution, functional magnetic resonance imaging (lfMRI) is a noninvasive technique with the potential to distinguish top-down and bottom-up signal contributions on the basis of laminar specific interactions between distal regions. Hitherto, lfMRI could not be demonstrated for either whole-brain distributed networks or for complex cognitive tasks. We show that lfMRI can reveal whole-brain directed networks during word reading. We identify distinct, language critical regions based on their association with the top-down signal stream and establish lfMRI for the noninvasive assessment of directed connectivity during task performance.

neuroscience↗

bioRxiv2018

Healthy Ageing and Sentence Production: Impaired Lexical Access in the Context of Intact Syntactic Planning

Healthy ageing does not affect all features of language processing equally. In this study, we investigated the effects of ageing on different processes involved in fluent sentence production, a complex task that requires the successful execution and coordination of multiple processes. In Experiment 1, we investigated age-related effects on the speed of syntax selection using a syntactic priming paradigm. Both young and older adults produced target sentences quicker following syntactically related primes compared to unrelated primes, indicating that syntactic facilitation effects are preserved with age. In Experiment 2, we investigated age-related effects in syntactic planning and lexical retrieval using a planning scope paradigm: participants described moving picture displays designed to elicit sentences with either initial coordinate or simple noun phrases and, on half of the trials, the second picture was previewed. Without preview, both age groups were slower to initiate sentences with larger coordinate phrases, suggesting a similar phrasal planning scope. However, age-related differences did emerge relating to the preview manipulation: while young adults displayed speed benefits of preview in both phrase conditions, older adults only displayed speed preview benefits within the initial phrase (coordinate condition). Moreover, preview outside the initial phrase (simple condition) caused older adults to become significantly more error-prone. Thus, while syntactic planning scope appears unaffected by ageing, older adults do appear to encounter problems with managing the activation and integration of lexical items into syntactic structures. Taken together, our findings indicate that healthy ageing disrupts the lexical, but not the syntactic, processes involved in sentence production.

neuroscience↗

bioRxiv2018

Evidence against preserved syntactic comprehension in healthy aging

We investigated age-related differences in syntactic comprehension in young and older adults. Most previous research found no evidence of age-related decline in syntactic processing. We investigated elementary syntactic comprehension of minimal sentences (e.g. I cook), minimizing the influence of working memory. We also investigated the contribution of semantic processing by comparing sentences containing real verbs (e.g. I cook) versus pseudoverbs (e.g. I spuff). We measured the speed and accuracy of detecting syntactic agreement errors (e.g. I cooks, I spuffs). We found that older adults were slower and less accurate than younger adults in detecting syntactic agreement errors for both real and pseudoverb sentences, suggesting there is age-related decline in syntactic comprehension. The age-related decline in accuracy was smaller for the pseudoverb sentences, and the decline in speed was larger for the pseudoverb sentences, compared to real verb sentences. We suggest that syntactic comprehension decline is stronger in the absence of semantic information, which causes older adults to produce slower responses in order to make more accurate decisions. In line with these findings, performance for older adults was positively related to a measure of processing speed capacity. Taken together, we found evidence that elementary syntactic processing abilities decline in healthy ageing.

neuroscience↗

bioRxiv2018

Memory encoding of syntactic information involves domain-general attentional resources. Evidence from dual-task studies

We investigate the type of attention (domain-general or language-specific) used during syntactic processing. We focus on syntactic priming: In this task, participants listen to a sentence that describes a picture (prime sentence), followed by a picture the participants need to describe (target sentence). We measure the proportion of times participants use the syntactic structure they heard in the prime sentence to describe the current target sentence as a measure of syntactic processing. Participants simultaneously conducted a motion-object tracking (MOT) task, a task commonly used to tax domain-general attentional resources. We manipulated the number of objects the participant had to track; we thus measured participants ability to process syntax while their attention is not-, slightly-, or overly-taxed. Performance in the MOT task was significantly worse when conducted as a dual-task compared to as a single task. We observed an inverted U-shaped curve on priming magnitude when conducting the MOT task concurrently with prime sentences (i.e., memory encoding), but no effect when conducted with target sentences (i.e., memory retrieval). Our results illustrate how, during the encoding of syntactic information, domain-general attention differentially affects syntactic processing, whereas during the retrieval of syntactic information domain-general attention does not influence syntactic processing.

neuroscience↗

bioRxiv2018

Dissociable effects of prediction and integration during language comprehension: Evidence from a large-scale study using brain potentials

Composing sentence meaning is easier for predictable words than for unpredictable words. Are predictable words genuinely predicted, or simply more plausible and therefore easier to integrate with sentence context? We addressed this persistent and fundamental question using data from a recent, large-scale (N = 334) replication study, by investigating the effects of word predictability and sentence plausibility on the N400, the brains electrophysiological index of semantic processing. A spatiotemporally fine-grained mixed effects multiple regression analysis revealed overlapping effects of predictability and plausibility on the N400, albeit with distinct spatiotemporal profiles. Our results challenge the view that the predictability-dependent N400 reflects the effects of either prediction or integration, and suggest that semantic facilitation of predictable words arises from a cascade of processes that activate and integrate word meaning with context into a sentence-level meaning.

neuroscience↗

bioRxiv2017

Fit to speak - Physical fitness is related to less language decline in ageing

Healthy ageing is associated with decline in cognitive abilities such as language. Aerobic fitness has been shown to ameliorate decline in some cognitive domains, but the potential benefits for language have not been examined. In a cross-sectional sample, we investigated the relationship between aerobic fitness and tip-of-the-tongue states. These are among the most frequent cognitive failures in healthy older adults and occur when a speaker knows a word but is unable to produce it. We found that healthy older adults indeed experience more tip-of-the-tongue states than young adults. Importantly, higher aerobic fitness levels decrease the probability of experiencing tip-of-the-tongue states in healthy older adults. Fitness-related differences in word finding abilities are observed over and above effects of age. This is the first demonstration of a link between aerobic fitness and language functioning in healthy older adults.

neuroscience↗

bioRxiv2017

Changes in alpha activity reveal that social opinion modulates attention allocation during face processing

AbstractParticipants performance differs when conducting a task in the presence of a secondary individual, moreover the opinion the participant has of this individual also plays a role. Using EEG, we investigated how previous interactions with, and evaluations of, an avatar in virtual reality subsequently influenced attentional allocation to the face of that avatar. We focused on changes in the alpha activity as an index of attentional allocation. We found that the onset of an avatars face whom the participant had developed a rapport with induced greater alpha suppression. This suggests greater attentional resources allocated to the interacted-with avatars. The evaluative ratings of the avatar induced a U-shaped change in alpha suppression, such that participants paid most attention when the avatar was rated as average. These results suggest that attentional allocation is thus an important element of how behaviour is altered in the presence of a secondary individual.

neuroscience↗

bioRxiv2017

Binding language: Structuring sentences through precisely timed oscillatory mechanisms

Syntactic binding refers to combining words into larger structures. Using EEG, we investigated the neural processes involved in syntactic binding. Participants were auditorily presented two-word sentences (i.e. a pronoun and pseudoverb such as she dotches, for which syntactic binding can take place) and wordlists (i.e. two pseudoverbs such as pob dotches, for which no binding can occur). Comparing these two conditions, we targeted syntactic binding while minimizing contributions of semantic binding and of other cognitive processes such as working memory. We found a converging pattern of results using two distinct analysis approaches: one approach using frequency bands as defined in previous literature, and one data-driven approach in which we looked at the entire range of frequencies between 3-30 Hz without the constraints of pre-defined frequency bands. In the syntactic binding (relative to the wordlist) condition, a power increase was observed in the alpha and beta frequency range shortly preceding the presentation of the target word that requires binding, which was maximal over frontal-central electrodes. Our interpretation is that these signatures reflect that language comprehenders expect the need for binding to occur. Following the presentation of the target word in a syntactic binding context (relative to the wordlist condition), an increase in alpha power maximal over a left lateralized cluster of frontal-temporal electrodes was observed. We suggest that this alpha increase relates to syntactic binding taking place. Taken together, our findings suggest that increases in alpha and beta power are reflections of distinct the neural processes underlying syntactic binding.

neuroscience↗

bioRxiv2017

Structural priming is supported by different components of non-declarative memory: Evidence from priming across the lifespan

Structural priming is the tendency to repeat syntactic structure across sentences and can be divided into short-term (prime to immediately following target) and long-term (across an experimental session) components. This study investigates how non-declarative memory could support both the transient, short-term and the persistent, long-term structural priming effects commonly seen in the literature. We propose that these characteristics are supported by different subcomponents of non-declarative memory: Perceptual and conceptual non-declarative memory respectively. Previous studies have suggested that these subcomponents age differently, with only conceptual memory showing age-related decline. By investigating how different components of structural priming vary across the lifespan, we aim to elucidate how non-declarative memory supports two seemingly different components of structural priming. In 167 participants ranging between 20 and 85 years old, we find no change in short-term priming magnitude and performance on perceptual tasks, whereas both long-term priming and conceptual memory vary with age. We suggest therefore that the two seemingly different components of structural priming are supported by different components of non-declarative memory. These findings have important implications for theoretical accounts of structural priming.

neuroscience↗