Sounds, Words, Sentences: Age-Related Changes Across Levels of Language Processing

Aging of lexical access in Chinese spoken word production: A picture-word interference study

It remains unknown how language-production processes decline with age. Using a picture-word interference task, the aim of this study was to investigate the influence of aging on lexical access and the contributions of language-specific and domain-general factors to semantic, phonological, and orthographic effects in Chinese spoken word production. After controlling for years of education, language comprehension, and domain-general cognitive abilities, we found a larger semantic interference effect for older speakers than for younger speakers, while the phonological effect and orthographic effect were comparable for the two age groups, supporting the transmission deficit hypothesis. Furthermore, discourse comprehension and general cognitive abilities were found to contribute to the phonological effect in older adults, but not in younger adults. Our findings indicate that both language-specific factors and domain-general factors contribute to the aging of spoken word production together.

The language network ages well: Preserved selectivity, lateralization, and within-network functional synchronization in older brains

Healthy aging is associated with structural and functional brain changes. However, cognitive abilities differ from one another in how they change with age: whereas executive functions, like working memory, show age-related decline, aspects of linguistic processing remain relatively preserved (Hartshorne et al., 2015). This heterogeneity of the cognitive-behavioral landscape in aging predicts differences among brain networks in whether and how they should change with age. To evaluate this prediction, we used individual-subject fMRI analyses ('precision fMRI') to examine the language-selective network (Fedorenko et al., 2024) and the Multiple Demand (MD) network, which supports executive functions (Duncan et al., 2020), in older adults (n=77) relative to young controls (n=470). In line with past claims, relative to young adults, the MD network of older adults shows weaker and less spatially extensive activations during an executive function task and reduced within-network functional synchronization. However, in stark contrast to the MD network, we find remarkable preservation of the language network in older adults. Their language network responds to language as strongly and selectively as in younger adults, and is similarly lateralized and internally synchronized. In other words, the language network of older adults looks indistinguishable from that of younger adults. Our findings align with behavioral preservation of language skills in aging and suggest that some networks remain young-like, at least on standard measures of function and connectivity.

Tailoring Semantic Interventions for Older Adults: Task-Focused and Person-Centered Approaches

In this narrative review, we explore the latest evidence on semantic interventions for older adults, including both prevention and rehabilitation/remediation efforts, discussing them particularly in the context of dementia. Cognitive interventions vary in their level of structure, encompassing standardized (task-focused tasks) and unstandardized tasks (person-centered tasks). These interventions also differ in their target: rehabilitation or prevention. Addressing semantic knowledge/semantic memory/semantics is important, primarily because its efficiency impacts other cognitive domains. Semantic tasks are commonly included in preventive and rehabilitation programs, typically as standardized tasks with pre-defined semantic referents. On the other hand, person-centered approaches introduce personally relevant semantics, allowing patients to share thoughts and experiences with expressive language. Although these approaches offer benefits beyond cognitive improvement, their lack of structure may pose challenges. Our question club (CQ) program blends structured activities with personally relevant semantics, aiming to harness the advantages of both methods. Additionally, in this narrative review, we discuss future challenges and directions in the field of semantic interventions.

The Costs (and Benefits?) of Effortful Listening for Older Adults: Insights from Simultaneous Electrophysiology, Pupillometry, and Memory

Although the impact of acoustic challenge on speech processing and memory increases as a person ages, older adults may engage in strategies that help them compensate for these demands. In the current preregistered study, older adults (n = 48) listened to sentences-presented in quiet or in noise-that were high constraint with either expected or unexpected endings or were low constraint with unexpected endings. Pupillometry and EEG were simultaneously recorded, and subsequent sentence recognition and word recall were measured. Like young adults in prior work, we found that noise led to increases in pupil size, delayed and reduced ERP responses, and decreased recall for unexpected words. However, in contrast to prior work in young adults where a larger pupillary response predicted a recovery of the N400 at the cost of poorer memory performance in noise, older adults did not show an associated recovery of the N400 despite decreased memory performance. Instead, we found that in quiet, increases in pupil size were associated with delays in N400 onset latencies and increased recognition memory performance. In conclusion, we found that transient variation in pupil-linked arousal predicted trade-offs between real-time lexical processing and memory that emerged at lower levels of task demand in aging. Moreover, with increased acoustic challenge, older adults still exhibited costs associated with transient increases in arousal without the corresponding benefits.

It takes a village: A multi-brain approach to studying multigenerational family communication

Grandparents play a critical role in child rearing across the globe. Yet, there is a shortage of neurobiological research examining the relationship between grandparents and their grandchildren. We employ multi-brain neurocomputational models to simulate how changes in neurophysiological processes in both development and healthy aging affect multigenerational inter-brain coupling - a neural marker that has been linked to a range of socio-emotional and cognitive outcomes. The simulations suggest that grandparent-child interactions may be paired with higher inter-brain coupling than parent-child interactions, raising the possibility that the former may be more advantageous under certain conditions. Critically, this enhancement of inter-brain coupling for grandparent-child interactions is more pronounced in tri-generational interactions that also include a parent, which may speak to findings that grandparent involvement in childrearing is most beneficial if the parent is also an active household member. Together, these findings underscore that a better understanding of the neurobiological basis of cross-generational interactions is vital, and that such knowledge can be helpful in guiding interventions that consider the whole family. We advocate for a community neuroscience approach in developmental social neuroscience to capture the diversity of child-caregiver relationships in real-world settings.

Age differences in central auditory system responses to naturalistic music

Aging influences the central auditory system leading to difficulties in the decoding and understanding of overlapping sound signals, such as speech in noise or polyphonic music. Studies on central auditory system evoked responses (ERs) have found in older compared to young listeners increased amplitudes (less inhibition) of the P1 and N1 and decreased amplitudes of the P2, mismatch negativity (MMN), and P3a responses. While preceding research has focused on simplified auditory stimuli, we here tested whether the previously observed age-related differences could be replicated with sounds embedded in medium and highly naturalistic musical contexts. Older (age 55-77 years) and younger adults (age 21-31 years) listened to medium naturalistic (synthesized melody) and highly naturalistic (studio recording of a music piece) stimuli. For the medium naturalistic music, the age group differences on the P1, N1, P2, MMN, and P3a amplitudes were all replicated. The age group differences, however, appeared reduced with the highly compared to the medium naturalistic music. The finding of lower P2 amplitude in older than young was replicated for slow event rates (0.3-2.9Hz) in the highly naturalistic music. Moreover, the ER latencies suggested a gradual slowing of the auditory processing time course for highly compared to medium naturalistic stimuli irrespective of age. These results support that age-related differences on ERs can partly be observed with naturalistic stimuli. This opens new avenues for including naturalistic stimuli in the investigation of age-related central auditory system disorders.

Delta-band neural tracking primarily reflects rule-based chunking instead of semantic relatedness between words

It is debated whether cortical responses matching the time scales of phrases and sentences mediate the mental construction of the syntactic chunks or are simply caused by the semantic properties of words. Here, we investigate to what extent delta-band neural responses to speech can be explained by semantic relatedness between words. To dissociate the contribution of semantic relatedness from sentential structures, participants listened to sentence sequences and paired-word sequences in which semantically related words repeated at 1 Hz. Semantic relatedness in the 2 types of sequences was quantified using a word2vec model that captured the semantic relation between words without considering sentential structure. The word2vec model predicted comparable 1-Hz responses with paired-word sequences and sentence sequences. However, empirical neural activity, recorded using magnetoencephalography, showed a weaker 1-Hz response to paired-word sequences than sentence sequences in a word-level task that did not require sentential processing. Furthermore, when listeners applied a task-related rule to parse paired-word sequences into multi-word chunks, 1-Hz response was stronger than that in word-level task on the same sequences. Our results suggest that cortical activity tracks multi-word chunks constructed by either syntactic rules or task-related rules, whereas the semantic relatedness between words contributes only in a minor way.

Neural tracking of linguistic and acoustic speech representations decreases with advancing age

BACKGROUND

Older adults process speech differently, but it is not yet clear how aging affects different levels of processing natural, continuous speech, both in terms of bottom-up acoustic analysis and top-down generation of linguistic-based predictions. We studied natural speech processing across the adult lifespan via electroencephalography (EEG) measurements of neural tracking.

GOALS

Our goals are to analyze the unique contribution of linguistic speech processing across the adult lifespan using natural speech, while controlling for the influence of acoustic processing. Moreover, we also studied acoustic processing across age. In particular, we focus on changes in spatial and temporal activation patterns in response to natural speech across the lifespan.

METHODS

52 normal-hearing adults between 17 and 82 years of age listened to a naturally spoken story while the EEG signal was recorded. We investigated the effect of age on acoustic and linguistic processing of speech. Because age correlated with hearing capacity and measures of cognition, we investigated whether the observed age effect is mediated by these factors. Furthermore, we investigated whether there is an effect of age on hemisphere lateralization and on spatiotemporal patterns of the neural responses.

RESULTS

Our EEG results showed that linguistic speech processing declines with advancing age. Moreover, as age increased, the neural response latency to certain aspects of linguistic speech processing increased. Also acoustic neural tracking (NT) decreased with increasing age, which is at odds with the literature. In contrast to linguistic processing, older subjects showed shorter latencies for early acoustic responses to speech. No evidence was found for hemispheric lateralization in neither younger nor older adults during linguistic speech processing. Most of the observed aging effects on acoustic and linguistic processing were not explained by age-related decline in hearing capacity or cognition. However, our results suggest that the effect of decreasing linguistic neural tracking with advancing age at word-level is also partially due to an age-related decline in cognition than a robust effect of age.

CONCLUSION

Spatial and temporal characteristics of the neural responses to continuous speech change across the adult lifespan for both acoustic and linguistic speech processing. These changes may be traces of structural and/or functional change that occurs with advancing age.

Speech comprehension in noisy environments: Evidence from the predictability effects on the N400 and LPC

Introduction

Speech comprehension involves context-based lexical predictions for efficient semantic integration. This study investigated how noise affects the predictability effect on event-related potentials (ERPs) such as the N400 and late positive component (LPC) in speech comprehension.

Methods

Twenty-seven listeners were asked to comprehend sentences in clear and noisy conditions (hereinafter referred to as "clear speech" and "noisy speech," respectively) that ended with a high-or low-predictability word during electroencephalogram (EEG) recordings.

Results

The study results regarding clear speech showed the predictability effect on the N400, wherein low-predictability words elicited a larger N400 amplitude than did high-predictability words in the centroparietal and frontocentral regions. Noisy speech showed a reduced and delayed predictability effect on the N400 in the centroparietal regions. Additionally, noisy speech showed a predictability effect on the LPC in the centroparietal regions.

Discussion

These findings suggest that listeners achieve comprehension outcomes through different neural mechanisms according to listening conditions. Noisy speech may be comprehended with a second-pass process that possibly functions to recover the phonological form of degraded speech through phonetic reanalysis or repair, thus compensating for decreased predictive efficiency.

Aging-Related Dissociation of Spatial and Temporal N400 in Sentence-Level Semantic Processing: Evidence From Source Analyses

Age-related differences in sentence-level lexical-semantic processes have been extensively studied, based on the N400 component of event-related potential (ERP). However, there is still a lack of understanding in this regard at the brain-region level. This study explores aging effects on sentence-level semantic processing by comparing the characteristics of the N400 ERP component and brain engagement patterns within individual N400 time windows for two age groups (16 younger adults aged 24.38 ± 3.88 years and 15 older adults aged 67.00 ± 5.04 years) during sentence processing with different plausibility conditions. Our results demonstrated that the N400 effect according to the plausibility condition occurred in different temporal windows in the two age groups, with a delay in the older group. Moreover, it was identified that there was a distinct difference between the groups in terms of the source location of the condition-dependent N400 effect even though no significant difference was derived in its magnitude itself at the sensor-level. Interestingly, the source analysis results indicated that the two groups involved different functional networks to resolve the same semantic violations: the younger group activated the regions corresponding to the typical lexical-semantic network more, whereas the older group recruited the regions belonging to the multiple-demand network more. The findings of this study could be used as a basis for understanding the aging brain in a linguistic context.

Lexical Effects on the Perceived Clarity of Noise-Vocoded Speech in Younger and Older Listeners

When listening to degraded speech, such as speech delivered by a cochlear implant (CI), listeners make use of top-down linguistic knowledge to facilitate speech recognition. Lexical knowledge supports speech recognition and enhances the perceived clarity of speech. Yet, the extent to which lexical knowledge can be used to effectively compensate for degraded input may depend on the degree of degradation and the listener's age. The current study investigated lexical effects in the compensation for speech that was degraded via noise-vocoding in younger and older listeners. In an online experiment, younger and older normal-hearing (NH) listeners rated the clarity of noise-vocoded sentences on a scale from 1 ("very unclear") to 7 ("completely clear"). Lexical information was provided by matching text primes and the lexical content of the target utterance. Half of the sentences were preceded by a matching text prime, while half were preceded by a non-matching prime. Each sentence also consisted of three key words of high or low lexical frequency and neighborhood density. Sentences were processed to simulate CI hearing, using an eight-channel noise vocoder with varying filter slopes. Results showed that lexical information impacted the perceived clarity of noise-vocoded speech. Noise-vocoded speech was perceived as clearer when preceded by a matching prime, and when sentences included key words with high lexical frequency and low neighborhood density. However, the strength of the lexical effects depended on the level of degradation. Matching text primes had a greater impact for speech with poorer spectral resolution, but lexical content had a smaller impact for speech with poorer spectral resolution. Finally, lexical information appeared to benefit both younger and older listeners. Findings demonstrate that lexical knowledge can be employed by younger and older listeners in cognitive compensation during the processing of noise-vocoded speech. However, lexical content may not be as reliable when the signal is highly degraded. Clinical implications are that for adult CI users, lexical knowledge might be used to compensate for the degraded speech signal, regardless of age, but some CI users may be hindered by a relatively poor signal.

Examining the context benefit in older adults: A combined behavioral-electrophysiologic word identification study

When listening to degraded speech, listeners can use high-level semantic information to support recognition. The literature contains conflicting findings regarding older listeners' ability to benefit from semantic cues in recognizing speech, relative to younger listeners. Electrophysiologic (EEG) measures of lexical access (N400) often show that semantic context does not facilitate lexical access in older listeners; in contrast, auditory behavioral studies indicate that semantic context improves speech recognition in older listeners as much or more as in younger listeners. Many behavioral studies of aging and the context benefit have employed signal degradation or alteration, whereas this stimulus manipulation has been absent in the EEG literature, a possible reason for the inconsistencies between studies. Here we compared the context benefit as a function of age and signal type, using EEG combined with behavioral measures. Non-native accent, a common form of signal alteration which many older adults report as a challenge in daily speech recognition, was utilized for testing. The stimuli included English sentences produced by native speakers of English and Spanish, containing target words differing in cloze probability. Listeners performed a word identification task while 32-channel cortical responses were recorded. Results show that older adults' word identification performance was poorer in the low-predictability and non-native talker conditions than the younger adults, replicating earlier behavioral findings. However, older adults did not show reductions or delays in the average N400 response as compared to younger listeners, suggesting no age-related reduction in predictive processing capability. Potential sources for discrepancies in the prior literature are discussed.

Age-related Changes in the Structure and Dynamics of the Semantic Network

Normal aging has variable effects on language comprehension, perhaps because comprehension mechanisms vary in their dependence on network structure versus network dynamics. To test claims that processing dynamics are more affected by age than structure, we used EEG to measure and compare the impact of neighborhood size, a core measure of the structure of the lexico-semantic network, and repetition, a simple measure of processing dynamics, on single word processing. Older adults showed robust effects of neighborhood size on the N400, comparable to those elicited by young adults, but reduced effects of repetition. Furthermore, older adults with greater verbal fluency, print exposure, and reading comprehension showed greater repetition effects, suggesting some older adults can maintain processing dynamics that are similar to those of young adults. Thus, the organizational structure of the semantic network seems stable across normal aging, but (some) older adults may struggle to adjust activation states within that network.

Connecting and considering: Electrophysiology provides insights into comprehension

The ability to rapidly and systematically access knowledge stored in long-term memory in response to incoming sensory information-that is, to derive meaning from the world-lies at the core of human cognition. Research using methods that can precisely track brain activity over time has begun to reveal the multiple cognitive and neural mechanisms that make this possible. In this article, I delineate how a process of connecting affords an effortless, continuous infusion of meaning into human perception. In a relatively invariant time window, uncovered through studies using the N400 component of the event-related potential, incoming sensory information naturally induces a graded landscape of activation across long-term semantic memory, creating what might be called "proto-concepts". Connecting can be (but is not always) followed by a process of further considering those activations, wherein a set of more attentionally demanding "active comprehension" mechanisms mediate the selection, augmentation, and transformation of the initial semantic representations. The result is a limited set of more stable bindings that can be arranged in time or space, revised as needed, and brought to awareness. With this research, we are coming closer to understanding how the human brain is able to fluidly link sensation to experience, to appreciate language sequences and event structures, and, sometimes, to even predict what might be coming up next.

Phonological and semantic similarity of misperceived words in babble: Effects of sentence context, age, and hearing loss

This study investigated how age and hearing loss influence the misperceptions made when listening to sentences in babble. Open-set responses to final words in sentences with low and high context were analyzed for younger adults with normal hearing and older adults with normal or impaired hearing. All groups performed similarly in overall accuracy but differed in error type. Misperceptions for all groups were analyzed according to phonological and semantic properties. Comparisons between groups indicated that misperceptions for older adults were more influenced by phonological factors. Furthermore, older adults with hearing loss omitted more responses. Overall, across all groups, results suggest that phonological confusions most explain misperceptions in low context sentences. In high context sentences, the meaningful sentence context appears to provide predictive cues that reduce misperceptions. When misperceptions do occur, responses tend to have greater semantic similarity and lesser phonological similarity to the target, compared to low context sentences. In this way, semantic similarity may index a postdictive process by which ambiguities due to phonological confusions are resolved to conform to the semantic context of the sentence. These patterns demonstrate that context, age, and hearing loss affect the misperceptions, and potential sentence interpretation, made when listening to sentences in babble.

Lexico-semantic access and audiovisual integration in the aging brain: Insights from mixed-effects regression analyses of event-related potentials

We investigated how aging modulates lexico-semantic processes in the visual (seeing written items), auditory (hearing spoken items) and audiovisual (seeing written items while hearing congruent spoken items) modalities. Participants were young and older adults who performed a delayed lexical decision task (LDT) presented in blocks of visual, auditory, and audiovisual stimuli. Event-related potentials (ERPs) revealed differences between young and older adults despite older adults' ability to identify words and pseudowords as accurately as young adults. The observed differences included more focalized lexico-semantic access in the N400 time window in older relative to young adults, stronger re-instantiation and/or more widespread activity of the lexicality effect at the time of responding, and stronger multimodal integration for older relative to young adults. Our results offer new insights into how functional neural differences in older adults can result in efficient access to lexico-semantic representations across the lifespan.

How the healthy ageing brain supports semantic binding during language comprehension

Semantic binding refers to constructing complex meaning based on elementary building blocks. Using electroencephalography (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 with 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), whereas in healthy older adults, we found an opposite binding signature about ~500 ms 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 with young adults.

The ERP correlates of self-knowledge in ageing

Self-knowledge is a type of personal semantic knowledge that concerns one's self-image and personal identity. It has most often been operationalized as the summary of one's personality traits ("I am a stubborn person"). Interestingly, recent studies have revealed that the neural correlates of self-knowledge can be dissociated from those of general semantic and episodic memory in young adults. However, studies of "dedifferentiation" or loss of distinctiveness of neural representations in ageing suggest that the neural correlates of self-knowledge might be less distinct from those of semantic and episodic memory in older adults. We investigated this question in an event-related potential (ERP) study with 28 young and 26 older adults while they categorised personality traits for their self-relevance (self-knowledge conditions), and their relevance to certain groups of people (general semantic condition). Participants then performed a recognition test for previously seen traits (episodic condition). The amplitude of the late positive component (LPC), associated with episodic recollection processes, differentiated the self-knowledge, general semantic, and episodic conditions in young adults, but not in older adults. However, in older adults, participants with higher composite episodic memory scores had more differentiated LPC amplitudes across experimental conditions. Moreover, consistent with the fact that age-related neural dedifferentiation may be material and region specific, in both age groups some differences between memory types were observed for the N400 component, associated with semantic processing. Taken together, these findings suggest that declarative memory subtypes are less distinct in ageing, but that the amount of differentiation varies with episodic memory function.

Dissociable electrophysiological measures of natural language processing reveal differences in speech comprehension strategy in healthy ageing

Healthy ageing leads to changes in the brain that impact upon sensory and cognitive processing. It is not fully clear how these changes affect the processing of everyday spoken language. Prediction is thought to play an important role in language comprehension, where information about upcoming words is pre-activated across multiple representational levels. However, evidence from electrophysiology suggests differences in how older and younger adults use context-based predictions, particularly at the level of semantic representation. We investigate these differences during natural speech comprehension by presenting older and younger subjects with continuous, narrative speech while recording their electroencephalogram. We use time-lagged linear regression to test how distinct computational measures of (1) semantic dissimilarity and (2) lexical surprisal are processed in the brains of both groups. Our results reveal dissociable neural correlates of these two measures that suggest differences in how younger and older adults successfully comprehend speech. Specifically, our results suggest that, while younger and older subjects both employ context-based lexical predictions, older subjects are significantly less likely to pre-activate the semantic features relating to upcoming words. Furthermore, across our group of older adults, we show that the weaker the neural signature of this semantic pre-activation mechanism, the lower a subject’s semantic verbal fluency score. We interpret these findings as prediction playing a generally reduced role at a semantic level in the brains of older listeners during speech comprehension and that these changes may be part of an overall strategy to successfully comprehend speech with reduced cognitive resources.

Do infants represent human actions cross-modally? An ERP visual-auditory priming study

Recent findings indicate that 7-months-old infants perceive and represent the sounds inherent to moving human bodies. However, it is not known whether infants integrate auditory and visual information in representations of specific human actions. To address this issue, we used ERPs to investigate infants' neural sensitivity to the correspondence between sounds and images of human actions. In a cross-modal priming paradigm, 7-months-olds were presented with the sounds generated by two types of human body movement, walking and handclapping, after watching the kinematics of those actions in either a congruent or incongruent manner. ERPs recorded from frontal, central and parietal electrodes in response to action sounds indicate that 7-months-old infants perceptually link the visual and auditory cues of human actions. However, at this age these percepts do not seem to be integrated in cognitive multimodal representations of human actions.

Online sentence processing impairments in agrammatic and logopenic primary progressive aphasia: Evidence from ERP

Evidence from psycholinguistic research indicates that sentence processing is impaired in Primary Progressive Aphasia (PPA), and more so in individuals with agrammatic (PPA-G) than logopenic (PPA-L) subtypes. Studies have mostly focused on offline sentence production ability, reporting impaired production of verb morphology (e.g., tense, agreement) and verb-argument structure (VAS) in PPA-G, and mixed findings in PPA-L. However, little is known about real-time sentence comprehension in PPA. The present study is the first to compare real-time semantic, morphosyntactic and VAS processing in individuals with PPA (10 with PPA-G and 9 with PPA-L), and in two groups of healthy (22 young and 19 older) individuals, using event-related potentials (ERP). Participants were instructed to listen to sentences that were either well-formed (n = 150) or contained a violation of semantics (e.g., *Owen was mentoring pumpkins at the party, n = 50), morphosyntax (e.g., *The actors was singing in the theatre, n = 50) or VAS (*Ryan was devouring on the couch, n = 50), and were required to perform a sentence acceptability judgment task while EEG was recorded. Results indicated that in the semantic task both healthy and PPA groups showed an N400 response to semantic violations, which was delayed in PPA and older (vs. younger) groups. Morphosyntactic violations elicited a P600 in both groups of healthy individuals and in PPA-L, but not in PPA-G. A similar P600 response was also found only in healthy individuals for VAS violations; whereas, abnormal ERP responses were observed in both PPA groups, with PPA-G showing no evidence of VAS violation detection and PPA-L showing a delayed and abnormally-distributed positive component that was negatively associated with offline sentence comprehension scores. These findings support characterizations of sentence processing impairments in PPA-G, by providing online evidence that VAS and morphosyntactic processing are impaired, in the face of substantially preserved semantic processing. In addition, the results indicate that on-line processing of VAS information may also be impaired in PPA-L, despite their near-normal accuracy on standardized language tests of argument structure production.

Age-related dissociation of N400 effect and lexical priming

The use of contextual information is an important capability to facilitate language comprehension. This can be shown by studying behavioral and neurophysiological measures of accelerated word recognition when semantically or phonemically related information is provided in advance, resulting in accompanying attenuation of the respective event-related potential, i.e. the N400 effect. Against the background of age-dependent changes in a broad variety of lexical capacities, we aimed to study whether word priming is accomplished differently in elderly compared to young persons. 19 young (29.9 ± 5.6 years) and 15 older (69.0 ± 7.2 years) healthy adults participated in a primed lexical decision task that required the classification of target stimuli (words or pseudo-words) following related or unrelated prime words. We assessed reaction time, task accuracy and N400 responses. Acceleration of word recognition by semantic and phonemic priming was significant in both groups, but resulted in overall larger priming effects in the older participants. Compared with young adults, the older participants were slower and less accurate in responding to unrelated word-pairs. The expected N400 effect was smaller in older than young adults, particularly during phonemic word and pseudo-word priming, with a rather similar N400 amplitude reduction by semantic relatedness. The observed pattern of results is consistent with preserved or even enhanced lexical context sensitivity in older compared to young adults. This, however, appears to involve compensatory cognitive strategies with higher lexical processing costs during phonological processing in particular, suggested by a reduced N400 effect in the elderly.

Early reading comprehension and speed of reading impairments in individuals with uncomplicated and complicated mild traumatic brain injury

PURPOSE

Several studies have investigated cognitive-communication disorders affecting oral expression skills following TBI but very few have dealt with reading comprehension abilities. The current study aims to measure reading comprehension and speed of reading in adults with uncomplicated and complicated mild traumatic brain injury (TBI) and to determine which demographic and TBI-related variables are predictive of their performance.

METHOD

The performances of three groups of participants were compared on the Chapman-Cook Speed of Reading Test (CCSRT). The CCSRT was administered in an acute care setting to 85 hospitalized participants with mild TBI showing traumatic cerebral lesions (complicated mild TBI), to 15 hospitalized participants with uncomplicated mild TBI (no cerebral lesions) and to 68 adults without TBI. Linear regression analyses were performed to determine which variables among sex, age, education, TBI severity (measured by the Glasgow Coma Scale score), speed of processing skills, and site of cerebral lesions significantly predicted CCSRT performances.

RESULTS

The control group showed a lower percentage of errors than both TBI groups. On the total score of the CCSRT, the uncomplicated and complicated TBI groups performed worse than the control group. Moreover, as age and speed of processing skills increased, and education decreased, the odds of having a lower score on the CCSRT increased.

CONCLUSION

These findings suggest that reading abilities are compromised after mild TBI. Furthermore, the CCSRT may be a useful bedside tool for clinicians who work with individuals with mild TBI.

Semantic Processing in Healthy Aging and Alzheimer's Disease: A Systematic Review of the N400 Differences

Semantic deficits are common in individuals with Alzheimer’s disease (AD). These deficits notably impact the ability to understand words. In healthy aging, semantic knowledge increases but semantic processing (i.e., the ability to use this knowledge) may be impaired. This systematic review aimed to investigate semantic processing in healthy aging and AD through behavioral responses and the N400 brain event-related potential. The results of the quantitative and qualitative analyses suggested an overall decrease in accuracy and increase in response times in healthy elderly as compared to young adults, as well as in individuals with AD as compared to age-matched controls. The influence of semantic association, as measured by N400 effect amplitudes, appears smaller in healthy aging and even more so in AD patients. Thus, semantic processing differences may occur in both healthy and pathological aging. The establishment of norms of healthy aging for these outcomes that vary between normal and pathological aging could eventually help early detection of AD.

Design and evaluation of the effectiveness of a corpus of congruent and incongruent English sentences for the study of event related potentials

OBJECTIVE

To design and evaluate the effectiveness of a stimulus material in eliciting the N400 event related potential (ERP).

DESIGN

A set of 700 semantically congruent and incongruent sentences was developed in accordance with current linguistic norms, and validated with an electroencephalography (EEG) study, in which the influence of age and gender on the N400 ERP magnitude was analysed.

STUDY SAMPLE

Forty-five normal-hearing subjects (19-57 years, 21 females) participated in the EEG study.

RESULTS

The stimulus material used in the EEG study elicited a robust N400 ERP, with a morphology consistent with the literature. Results also showed no statistically significant effect of age or gender on the N400 magnitude.

CONCLUSIONS

The material presented in this paper constitutes the largest complete stimulus set suitable for both auditory and text-based N400 experiments. This material may help facilitate the efficient implementation of future N400 ERP studies, as well as promote standardisation and consistency across studies.

Semantic Processing in Autism Spectrum Disorders Is Associated With the Timing of Language Acquisition: A Magnetoencephalographic Study

Individuals with autism show difficulties in using sentence context to identify the correct meaning of ambiguous words, such as homonyms. In this study, the brain basis of sentence context effects on word understanding during reading was examined in autism spectrum disorder (ASD) and typical development (TD) using magnetoencephalography. The correlates of a history of developmental language delay in ASD were also investigated. Event related field responses at early (150 ms after the onset of a final word) and N400 latencies are reported for three different types of sentence final words: dominant homonyms, subordinate homonyms, and unambiguous words. Clear evidence for semantic access was found at both early and conventional N400 latencies in both TD participants and individuals with ASD with no history of language delay. By contrast, modulation of evoked activity related to semantic access was weak and not significant at early latencies in individuals with ASD with a history of language delay. The reduced sensitivity to semantic context in individuals with ASD and language delay was accompanied by strong right hemisphere lateralization at early and N400 latencies; such strong activity was not observed in TD individuals and individuals with ASD without a history of language delay at either latency. These results provide new evidence and support for differential neural mechanisms underlying semantic processing in ASD, and indicate that delayed language acquisition in ASD is associated with different lateralization and processing of language.

Age-related changes in the neural dynamics of bottom-up and top-down processing during visual object recognition: an electrophysiological investigation

When recognizing objects in our environments, we rely on both what we see and what we know. While older adults often display increased sensitivity to top-down influences of contextual information during object recognition, the locus of this increased sensitivity remains unresolved. To examine the effects of aging on the neural dynamics of bottom-up and top-down visual processing during rapid object recognition, we probed the differential effects of object perceptual ambiguity and scene context congruity on specific EEG event-related potential components indexing dissociable processes along the visual processing stream. Older adults displayed larger behavioral scene congruity effects than young adults. Older adults' larger visual P2 amplitudes to object perceptual ambiguity (as opposed to the scene congruity P2 effects in young adults) suggest continued resolution of perceptual ambiguity that interfered with scene congruity processing, while post-perceptual semantic integration (as indexed by N400) remained largely intact. These findings suggest that compromised bottom-up perceptual processing in healthy aging leads to an increased involvement of top-down processes to resolve greater perceptual ambiguity during object recognition.

The N400 for brain computer interfacing: complexities and opportunities

The N400 is an event related potential that is evoked in response to conceptually meaningful stimuli. It is for instance more negative in response to incongruent than congruent words in a sentence, and more negative for unrelated than related words following a prime word. This sensitivity to semantic content of a stimulus in relation to the mental context of an individual makes it a signal of interest for Brain Computer Interfaces. A complicating aspect is the number of factors that can affect the N400 amplitude. In this paper, we provide an accessible overview of this range of N400 effects, and survey the three main BCI application areas that currently exploit the N400: (1) exploiting the semantic processing of faces to enhance matrix speller performance, (2) detecting language processing in patients with Disorders of Consciousness, and (3) using semantic stimuli to probe what is on a user's mind. Drawing on studies from these application areas, we illustrate that the N400 can successfully be exploited for BCI purposes, but that the signal-to-noise ratio is a limiting factor, with signal strength also varying strongly across subjects. Furthermore, we put findings in context of the general N400 literature, noting open questions and identifying opportunities for further research.

How the Brain Understands Spoken and Sung Sentences

The present study investigates whether meaning is similarly extracted from spoken and sung sentences. For this purpose, subjects listened to semantically correct and incorrect sentences while performing a correctness judgement task. In order to examine underlying neural mechanisms, a multi-methodological approach was chosen combining two neuroscientific methods with behavioral data. In particular, fast dynamic changes reflected in the semantically associated N400 component of the electroencephalography (EEG) were simultaneously assessed with the topographically more fine-grained vascular signals acquired by the functional near-infrared spectroscopy (fNIRS). EEG results revealed a larger N400 for incorrect compared to correct sentences in both spoken and sung sentences. However, the N400 was delayed for sung sentences, potentially due to the longer sentence duration. fNIRS results revealed larger activations for spoken compared to sung sentences irrespective of semantic correctness at predominantly left-hemispheric areas, potentially suggesting a greater familiarity with spoken material. Furthermore, the fNIRS revealed a widespread activation for correct compared to incorrect sentences irrespective of modality, potentially indicating a successful processing of sentence meaning. The combined results indicate similar semantic processing in speech and song.

What's "left"? Hemispheric sensitivity to predictability and congruity during sentence reading by older adults

A number of studies have found that older adults' sentence processing tends not to be characterized by the prediction-related effects attested for young adults. Here, we further probed older adults' sensitivity to predictability and congruity by recording event-related brain potentials (ERPs) as adults over age 60 read pairs of sentences, which ended with either the expected word, an unexpected word from the same semantic category, or an unexpected word from a different category. Half of the contexts were highly constraining. Consistent with patterns attested when older adults listened to these same materials (Federmeier et al., 2002), N400s, on average, were smaller to expected than to unexpected words, but did not show constraint-related reductions for unexpected words that shared features with the most predictable completion (an effect well-attested in young adults). This pattern resembles that seen in young adults for right-hemisphere-biased processing. To assess whether older adults retain young-like hemispheric asymmetries but recruit right hemisphere mechanisms more, we examined responses to the target words using visual half-field presentation. Whereas young adults show an asymmetric pattern, with prediction-related N400 amplitude reductions for left- but not right-hemisphere-initiated processing (Federmeier and Kutas, 1999b), older adults showed no reliable processing asymmetries and no evidence for prediction with left hemisphere-initiated presentation. The results suggest that left hemisphere mechanisms important for prediction during language processing are less efficacious in older adulthood.

A MEG study of the neural substrates of semantic processing in semantic variant primary progressive aphasia

Despite a well-documented pattern of semantic impairment, the patterns of brain activation during semantic processing in semantic variant primary progressive aphasia (svPPA) still remain poorly understood. In the current study, one svPPA patient (EC) and six elderly controls carried out a general-level semantic categorization task while their brain activity was recorded using magnetoencephalography (MEG). Despite similar behavioral performance, EC showed hyperactivation of the left inferior temporal gyrus (ITG) and right anterior temporal lobe (ATL) relative to controls. This suggests that periatrophic regions within the ATL region may support preserved semantic abilities in svPPA.

What does "it" mean, anyway? Examining the time course of semantic activation in reference resolution

Pronouns serve a critical referential function, yet the cognitive processes engaged during pronoun comprehension remain incompletely understood. One view is that encountering a pronoun leads the comprehender to reactivate the semantic features of its antecedent. We examined this by manipulating the concreteness of a noun antecedent and assessing whether an Event Related Potential (ERP) concreteness effect was elicited at a downstream pronoun. We observed a robust concreteness effect at the noun, but no similar effect at the pronoun. We also examined whether N400 semantic priming from the antecedent would increase on content words shortly following the pronoun, relative to those preceding it. Again, although we observed semantic priming following the noun, it did not increase following the pronoun. Our data suggest that pronouns do not induce the activation of (much) new semantic information in long-term memory, perhaps instead triggering an attentional shift towards their antecedents' extant representations within working memory.

Acute prediction of outcome and cognitive-communication impairments following traumatic brain injury: The influence of age, education and site of lesion

BACKGROUND

Communication impairment following a traumatic brain injury (TBI) has been well documented, yet information regarding communication skills in the acute period following the injury is limited in the literature. Also, little is known about the influence of TBI severity (mild, moderate or severe) on cognitive-communication impairments and how these impairments are related to short-term functional outcome. The goal of this study was to assess the performance of adults with mild, moderate and severe TBI on different language tests and to determine how this performance is related to functional capacity. We also aimed to explore which variables among age, sex, education, TBI severity and site of cerebral damage would predict initial language impairments.

METHODS

Several language tests were administered to a sample of 145 adult patients with TBI of a range of severities admitted to an acute care service and to 113 healthy participants from the community.

RESULTS

TBI patients of a range of severities performed poorly on all language tests in comparison to the healthy controls. In addition, patients with mild TBI performed better than the moderate and severe groups, except on the reading test and on the semantic naming test. In addition, their performance on verbal fluency, conversational discourse and procedural discourse tasks predicted acute functional outcome. Finally, age, education and TBI severity and site of lesion predicted some language performance. A left temporal lesion was associated with poorer performance in conversational discourse and auditory comprehension tasks, a left frontal lesion with a decrease in the verbal fluency results and a right parietal lesion with decreased auditory comprehension and reasoning skills.

CONCLUSION

Health care professionals working in the acute care setting should be aware of the possible presence of cognitive-communication impairments in patients with TBI, even for those with mild TBI. These deficits can lead to functional communication problems and assistance may be required for tasks frequently encountered in acute care requiring intact comprehension and expression.

Knowledge and learning of verb biases in amnesia

Verb bias-the co-occurrence frequencies between a verb and the syntactic structures it may appear with-is a critical and reliable linguistic cue for online sentence processing. In particular, listeners use this information to disambiguate sentences with multiple potential syntactic parses (e.g., Feel the frog with the feather.). Further, listeners dynamically update their representations of specific verbs in the face of new evidence about verb-structure co-occurrence. Yet, little is known about the biological memory systems that support the use and dynamic updating of verb bias. We propose that hippocampal-dependent declarative (relational) memory represents a likely candidate system because it has been implicated in the flexible binding of relational co-occurrences and in statistical learning. We explore this question by testing patients with severe and selective deficits in declarative memory (anterograde amnesia), and demographically matched healthy participants, in their on-line interpretation of ambiguous sentences and the ability to update their verb bias with experience. We find that (1) patients and their healthy counterparts use existing verb bias to successfully interpret on-line ambiguity, however (2) unlike healthy young adults, neither group updated these biases in response to recent exposure. These findings demonstrate that using existing representations of verb bias does not necessitate involvement of the declarative memory system, but leave open the question of whether the ability to update representations of verb-specific biases requires hippocampal engagement.

Reduced Syntactic Processing Efficiency in Older Adults During Sentence Comprehension

Researchers have frequently reported an age-related decline in semantic processing during sentence comprehension. However, it remains unclear whether syntactic processing also declines or whether it remains constant as people age. In the present study, 26 younger adults and 20 older adults were recruited and matched in terms of working memory, general intelligence, verbal intelligence and fluency. They were then asked to make semantic acceptability judgments while completing a Chinese sentence reading task. The behavioral results revealed that the older adults had significantly lower accuracy on measures of semantic and syntactic processing compared to younger adults. Event-related potential (ERP) results showed that during semantic processing, older adults had a significantly reduced amplitude and delayed peak latency of the N400 compared to the younger adults. During syntactic processing, older adults also showed delayed peak latency of the P600 relative to younger adults. Moreover, while P600 amplitude was comparable between the two age groups, larger P600 amplitude was associated with worse performance only in the older adults. Together, the behavioral and ERP data suggest that there is an age-related decline in both semantic and syntactic processing, with a trend toward lower efficiency in syntactic ability.

Contextual constraints on lexico-semantic processing in aging: Evidence from single-word event-related brain potentials

The current study reports the effects of accumulating contextual constraints on neural indices of lexico-semantic processing (i.e., effects of word frequency and orthographic neighborhood) as a function of normal aging. Event-related brain potentials were measured from a sample of older adults as they read sentences that were semantically congruent, provided only syntactic constraints (syntactic prose), or were random word strings. A linear mixed-effects modeling approach was used to probe the effects of accumulating contextual constraints on N400 responses to individual words. Like young adults in prior work, older adults exhibited a classic word position context effect on the N400 in congruent sentences, although the magnitude of the effect was reduced in older relative to younger adults. Moreover, by modeling single-word variability in N400 responses, we observed robust effects of orthographic neighborhood density that were larger in older adults than the young, and preserved effects word frequency. Importantly, in older adults, frequency effects were not modulated by accumulating contextual constraints, unlike in the young. Collectively, these findings indicate that older adults are less likely (or able) to use accumulating top-down contextual constraints, and therefore rely more strongly on bottom-up lexical features to guide semantic access of individual words during sentence comprehension.

Age-related reduction of adaptive brain response during semantic integration is associated with gray matter reduction

While aging is associated with increased knowledge, it is also associated with decreased semantic integration. To investigate brain activation changes during semantic integration, a sample of forty-eight 25–75 year-old adults read sentences with high cloze (HC) and low cloze (LC) probability while functional magnetic resonance imaging was conducted. Significant age-related reduction of cloze effect (LC vs. HC) was found in several regions, especially the left middle frontal gyrus (MFG) and right inferior frontal gyrus (IFG), which play an important role in semantic integration. Moreover, when accounting for global gray matter volume reduction, the age-cloze correlation in the left MFG and right IFG was absent. The results suggest that brain structural atrophy may disrupt brain response in aging brains, which then show less brain engagement in semantic integration.

Event-related brain potentials reveal age-related changes in parafoveal-foveal integration during sentence processing

Normative aging is associated with deficits in visual acuity and cognitive control that impact the allocation of visual attention, but little is known about how those changes affect information extraction and integration during visual language comprehension in older adulthood. In the current study, we used a visual hemi-field flanker RSVP paradigm with event-related brain potentials to study how older readers process fine-grained aspects of semantic expectancy in parafoveal and foveal vision. Stimuli consisted of high constraint sentences with expected, unexpected but plausible, or anomalous parafoveal target words, as well as low constraint sentences with neutral but expected target words. Older adults showed graded parafoveal N400 effects that were strikingly similar to younger readers, indicating intact parafoveal semantic processing. However, whereas young adults were able to use this parafoveal pre-processing to facilitate subsequent foveal viewing, resulting in a reduced foveal N400 effect, older adults were not able to. Instead, older adults re-processed the semantics of words in foveal vision, resulting in a larger foveal N400 effect relative to the young. Collectively, our findings suggest that although parafoveal semantic processing per se is preserved in aging, there exists an age-related deficit in the ability to rapidly integrate parafoveal and foveal visual semantic representations.

Pace Yourself: Intraindividual Variability in Context Use Revealed by Self-paced Event-related Brain Potentials

Event-related brain potentials (ERPs) have revealed multiple mechanisms by which contextual constraints impact language processing. At the same time, little work has examined the trial-to-trial dynamics of context use in the brain. In the current study, we probed intraindividual variability in behavioral and neural indices of context processing during reading. In a concurrent self-paced reading and ERP paradigm, participants read sentences that were either strongly or weakly constraining completed with an expected or unexpected target word. Our findings revealed substantial within-subject variability in behavioral and neural responses to contextual constraints. First, context-based amplitude reductions of the N400, a component linked to semantic memory access, were largest among trials eliciting the slowest RTs. Second, the RT distribution of unexpected words in strongly constraining contexts was positively skewed, reflecting an increased proportion of very slow RTs to trials that violated semantic predictions. Among those prediction-violating trials eliciting faster RTs, a late sustained anterior positivity was observed. However, among trials producing the differentially slowed RTs to prediction violations, we observed a markedly earlier effect of constraint in the form of an anterior N2, a component linked to conflict resolution and the cognitive control of behavior. The current study provides the first neurophysiological evidence for the direct role of cognitive control functions in the volitional control of reading. Collectively, our findings suggest that context use varies substantially within individual participants and that coregistering behavioral and neural indices of online sentence processing offers a window into these single-item dynamics.

Preliminary Investigation of the Passively Evoked N400 as a Tool for Estimating Speech-in-Noise Thresholds

PURPOSE

Speech-in-noise testing relies on a number of factors beyond the auditory system, such as cognitive function, compliance, and motor function. It may be possible to avoid these limitations by using electroencephalography. The present study explored this possibility using the N400.

METHOD

Eleven adults with typical hearing heard high-constraint sentences with congruent and incongruent terminal words in the presence of speech-shaped noise. Participants ignored all auditory stimulation and watched a video. The signal-to-noise ratio (SNR) was varied around each participant's behavioral threshold during electroencephalography recording. Speech was also heard in quiet.

RESULTS

The amplitude of the N400 effect exhibited a nonlinear relationship with SNR. In the presence of background noise, amplitude decreased from high (+4 dB) to low (+1 dB) SNR but increased dramatically at threshold before decreasing again at subthreshold SNR (-2 dB).

CONCLUSIONS

The SNR of speech in noise modulates the amplitude of the N400 effect to semantic anomalies in a nonlinear fashion. These results are the first to demonstrate modulation of the passively evoked N400 by SNR in speech-shaped noise and represent a first step toward the end goal of developing an N400-based physiological metric for speech-in-noise testing.

Looking at the Sunny Side of Life

Studies of the negativity bias have demonstrated that negative information has a stronger influence than positive information in a wide range of cognitive domains. At odds with this literature is extensive work now documenting emotional and motivational shifts that result in a positivity effect in older adults. It remains unclear, however, whether this age-related positivity effect results from increases in processing of positive information or from decreases in processing of negative information. Also unknown is the specific time course of development from a negative bias to an apparently positive one. The present study was designed to investigate the negativity bias across the life span using an event-related potential measure of responding to emotionally valenced images. The results suggest that neural reactivity to negative images declines linearly with age, but responding to positive images is surprisingly age invariant across most of the adult life span.