Effects of task types and time interval conditions on age-related decline in verbal working memory.

Age-related differences in working memory (WM) components were investigated by manipulating the time interval and interference effects between phonological and semantic judgment tasks to identify tasks to best discriminate between younger and older groups. The 96 participants (young = 48; old = 48) prospectively performed two task types of WM, with phonological and semantic judgment tasks, which were administered while varying the three interval conditions: 1-s unfilled (UF), 5-s UF, and 5-s filled (F). The main effect for age was significant in the semantic judgment task but not in the phonological judgment task. The main effect for the interval conditions were significant in both tasks. A 5-s UF condition applied to a semantic judgment task could significantly differentiate the older group from the younger group. Differential effects of time interval manipulation in semantic and phonological processing are involved in WM resources. The older group could be differentiated by varying the task types and interval conditions, indicating that the semantic-related WM burdens may contribute to a superior differential diagnosis of aging-related WM decline.

Language treatment effects on communicative abilities and working memory in Korean-speaking agrammatic Broca's aphasia caused by moyamoya disease: Phase II evidence from a case study.

The present study reports on the language treatment outcomes from sentence- and story-level linguistic facilitation and its generalization effect on communicative abilities, working memory, and sentence processing in the case of an adult with Moyamoya Disease (MMD). After treatment,the patient's overall performance, including the Aphasia Quotient, and sentence processing ability as measured by language testing, were improved. Furthermore, the treatment effects were generalizable to working memory abilities. Our case study conveys clinically meaningful implications since it is the first report on the effects of language treatment on linguistic and cognitive domains for an individual with MMD-induced agrammatic Broca's aphasia.

Effects of age, working memory, and word order on passive-sentence comprehension: evidence from a verb-final language.

BACKGROUND: The purpose of the current study was to investigate the effects of working-memory (WM) capacity on age-related changes in abilities to comprehend passive sentences when the word order was systematically manipulated. METHODS: A total of 134 individuals participated in the study. The sentence-comprehension task consisted of the canonical and non-canonical word-order conditions. A composite measure of WM scores was used as an index of WM capacity. RESULTS: Participants exhibited worse performance on sentences with non-canonical word order than canonical word order. The two-way interaction between age and WM was significant, suggesting that WM effects were greater than age effects on the task. CONCLUSIONS: WM capacity effects on passive-sentence comprehension increased dramatically as people aged, suggesting that those who have larger WM capacity are less vulnerable to age-related changes in sentence-comprehension abilities. WM capacity may serve as a cognitive reserve associated with sentence-comprehension abilities for elderly adults.

The Effects of Verb Argument Complexity on Verb Production in Persons with Aphasia: Evidence from a Subject-Object-Verb Language.

The purpose of the study was to investigate the effects of verb argument complexity on verb production in individuals with aphasia using a verb-final language. The verb-argument complexity was examined by the number of arguments (1-, 2-, and 3-place) and the types of arguments (unaccusative vs. unergative comparisons). Fifteen Korean-speaking individuals with aphasia and 16 normal controls participated in the study. A confrontation naming task was used to elicit verb production with a total of 36 items for each verb type (1-place unergative, 1-place unaccusative, 2-place, and 3-place verbs). Individuals with aphasia presented lower mean percentage correctness in 3-place than in 1-place verbs, and showed differentially greater difficulties with unaccusative constructions than with unergative verbs, compared to the control group. The effects of verb-argument complexity were clearly observed in Korean-speaking individuals with aphasia. The effects of the number of arguments were observed most clearly in Broca's and Wernicke's types of aphasia and individuals with lower overall aphasia severity. The effects of Korean unaccusativity manifested across aphasia groups. General patterns of verb-argument complexity in Korean were consistent with previous findings in English.

Age-related changes in connected speech production: evidence from eye-tracking in the culturally adapted picture description task.

Purpose: Age-related changes in connected speech production remain a subject of debate, yielding inconsistent findings across various tasks and measures. This study aimed to investigate the effects of aging on picture description tasks using two types of pictures: a standardized picture (the Beach picture) and a culturally and linguistically modified picture tailored for Korean speakers (the Han River picture). Method: Twenty-four young adults and 22 older adults participated in two picture description tasks while their eye movements were recorded. Word-level linguistic variables were used to assess informativeness (Correct Information Units per minute) and productivity (noun and verb counts per utterance) of connected speech production. Eye-movement measures were employed to evaluate real-time cognitive processing associated with planning connected speech (pre-speech fixation counts and durations; eye fixations before the speech onset of each utterance). Results and conclusions: The findings revealed age-related declines in linguistic measures, with older adults exhibiting decreased CIUs per minute and smaller counts of nouns and verbs per utterance. Age-related changes in eye movement measures were evident in that older adults displayed longer pre-speech fixation durations. Unlike younger adults, older adults exhibited higher pre-speech fixation counts on the Han River picture compared to the Beach picture, suggesting cognitive challenges in performing the task that requires producing more words and detailed descriptions. These results suggest that aging is associated with reduced informativeness and productivity of connected speech, as well as a decline in cognitive processing efficiency.

Coordinating Words and Sentences: Detecting Age-Related Changes in Language Production.

PURPOSE: The purpose of this study was to examine whether older adults exhibit reduced abilities in coordinating lexical retrieval and syntactic formulation during sentence production and whether an individual's working memory capacity predicts age-related changes in sentence production. METHOD: A total of 124 Korean-speaking individuals (79 young and 45 older adults) completed a lexical priming sentence production task. The participants described a target picture (a dog biting a monkey) after reading either an agent (dog) or a theme (monkey) prime word. The proportion of passive sentences was used as the dependent variable. RESULTS: When the theme noun was primed, older adults produced fewer passive sentences than young adults. Working memory tasks significantly predicted individual differences in the sentence production of older adults. CONCLUSIONS: With aging, the ability to efficiently formulate syntactic structures in coordination with varying lexical information declines. Among older adults, age-related changes in these sentence production processes are associated with reduced working memory. Our constrained language production task is sensitive to detecting aging effects.

Cross-Linguistic and Multicultural Considerations in Evaluating Bilingual Adults With Aphasia.

PURPOSE: The current study delineated a clinical and theoretical framework that clinicians and researchers can use to guide the assessment of bilingual aphasia at morphosyntactic, lexical-semantic, and phonological levels of language processing. METHOD: This tutorial outlines cross-linguistic and multicultural considerations that should be addressed in evaluating bilingual adults with aphasia (BWAs). RESULTS: At the morphosyntactic level, we presented three features that should be taken into account when evaluating linguistic symptoms in languages considering whether they are typologically similar or dissimilar: word order, pro(noun)-drop, and morphological inflections of verbs. We suggest that clinicians need to conduct additional error analyses that reflect typological differences in syntactic templates, argument-deletion phenomena, and morphological inflections to better understand linguistic characteristics of impairments arising from the interactions of the two languages that may differ in many ways. At the lexical-semantic level, we addressed three cross-linguistic features that may impact naming performance in BWAs: cognates, lexical frequency, and semantic typicality. The presence of cognates between the two languages can lead to differential interpretations of naming performance. In addition, the same lexical items may exhibit varying lexical frequency and typicality across languages due to cultural and linguistic differences. We suggest that clinicians should thoroughly prepare the testing items considering the linguistic distance. Finally, we emphasized differences in segmental and suprasegmental features of phonology that could contribute to cross-linguistic phenomena during assessment of two or more languages. CONCLUSIONS: This cross-linguistic assessment framework contributes to a better understanding of linguistic impairments and communication difficulties experienced by BWAs. This framework can be utilized in current clinical practice to facilitate culturally and linguistically appropriate assessment and treatment approaches for BWAs.

Interplay of Semantic Plausibility and Word Order Canonicity in Sentence Processing of People With Aphasia Using a Verb-Final Language.

PURPOSE: The Western Aphasia Battery is widely used to assess people with aphasia (PWA). Sequential Commands (SC) is one of the most challenging subtests for PWA. However, test items confound linguistic factors that make sentences difficult for PWA. The current study systematically manipulated semantic plausibility and word order in sentences like those in SC to examine how these factors affect comprehension deficits in aphasia. METHOD: Fifty Korean speakers (25 PWA and 25 controls) completed a sentence-picture matching task that manipulated word order (canonical vs. noncanonical) and semantic plausibility (plausible vs. less plausible). Analyses focused on accuracy and aimed to identify sentence types that best discriminate the groups. Additionally, we explored which sentence type serves as the best predictor of aphasia severity. RESULTS: PWA demonstrated greater difficulties in processing less plausible sentences than plausible ones compared to the controls. Across the groups, noncanonical and less plausible sentences elicited lower accuracy than canonical and plausible sentences. Notably, the accuracy of PWA and control groups differed in noncanonical and less plausible sentences. Additionally, aphasia severity significantly correlated with less plausible sentences. CONCLUSION: Even in languages with flexible word order, PWA find it challenging to process sentences with noncanonical syntactic structures and less plausible semantic roles.

Eye-movement reveals word order effects on comparative sentences in older adults using a verb-final language.

Objectives: This study aimed to examine age-related differences in the comprehension of Korean comparative sentences with varying word orders by employing both offline and online measures, and to investigate how variations in word order affect sentence processing across different age groups. Methods: A total of 52 monolingual native Korean speakers, 26 young adults, and 26 older adults, completed a sentence-picture-matching task under two word order conditions: comparative-first and nominative-first. Offline measures included accuracy and response time, while an online method involved eye-tracking within the Visual World Paradigm. Data analyses were performed using linear and generalized linear mixed-effects models. Results: Older adults demonstrated lower accuracy and longer response times compared to younger individuals. Distinctive fixation patterns were observed, particularly in the sentential-final phrase, across different age groups. Specifically, nominative-first sentences elicited greater target advantage scores among younger adults, whereas older adults showed higher scores in comparative-first sentences. Conclusion: The study highlights the potential of comparative sentences in elucidating age-related changes in sentence comprehension. These differences were evident not only in offline tasks but also in real-time processing, as evidenced by eye-tracking data. The findings suggest distinct processing strategies employed by young and older adults and underscore the importance of considering both syntactic and semantic cues in sentence comprehension.

Speech synthesis from three-axis accelerometer signals using conformer-based deep neural network.

Silent speech interfaces (SSIs) have emerged as innovative non-acoustic communication methods, and our previous study demonstrated the significant potential of three-axis accelerometer-based SSIs to identify silently spoken words with high classification accuracy. The developed accelerometer-based SSI with only four accelerometers and a small training dataset outperformed a conventional surface electromyography (sEMG)-based SSI. In this study, motivated by the promising initial results, we investigated the feasibility of synthesizing spoken speech from three-axis accelerometer signals. This exploration aimed to assess the potential of accelerometer-based SSIs for practical silent communication applications. Nineteen healthy individuals participated in our experiments. Five accelerometers were attached to the face to acquire speech-related facial movements while the participants read 270 Korean sentences aloud. For the speech synthesis, we used a convolution-augmented Transformer (Conformer)-based deep neural network model to convert the accelerometer signals into a Mel spectrogram, from which an audio waveform was synthesized using HiFi-GAN. To evaluate the quality of the generated Mel spectrograms, ten-fold cross-validation was performed, and the Mel cepstral distortion (MCD) was chosen as the evaluation metric. As a result, an average MCD of 5.03 ± 0.65 was achieved using four optimized accelerometers based on our previous study. Furthermore, the quality of generated Mel spectrograms was significantly enhanced by adding one more accelerometer attached under the chin, achieving an average MCD of 4.86 ± 0.65 (p < 0.001, Wilcoxon signed-rank test). Although an objective comparison is difficult, these results surpass those obtained using conventional SSIs based on sEMG, electromagnetic articulography, and electropalatography with the fewest sensors and a similar or smaller number of sentences to train the model. Our proposed approach will contribute to the widespread adoption of accelerometer-based SSIs, leveraging the advantages of accelerometers like low power consumption, invulnerability to physiological artifacts, and high portability.

Pupillometry as a window to detect cognitive aging in the brain.

This study investigated whether there are aging-related differences in pupil dilation (pupillometry) while the cognitive load is manipulated using digit- and word-span tasks. A group of 17 younger and 15 cognitively healthy older adults performed digit- and word-span tasks. Each task comprised three levels of cognitive loads with 10 trials for each level. For each task, the recall accuracy and the slope of pupil dilation were calculated and analyzed. The raw signal of measured pupil size was low-pass filtered and interpolated to eliminate blinking artifacts and spike noises. Two-way ANOVA was used for statistical analyses. For the recall accuracy, the significant group differences emerged as the span increases in digit-span (5- vs. 7-digit) and word-span (4- vs. 5-word) tasks, while the group differences were not significant on 3-digit- and 3-word-span tasks with lower cognitive load. In digit-span tasks, there was no aging-related difference in the slope of pupil dilation. However, in word-span tasks, the slope of pupil dilation differed significantly between two groups as cognitive load increased, indicating that older adults presented a higher pupil dilation slope than younger adults especially under the conditions with higher cognitive load. The current study found significant aging effects in the pupil dilations under the more cognitive demanding span tasks when the types of span tasks varied (e.g., digit vs. word). The manipulations successfully elicited differential aging effects, given that the aging effects became most salient under word-span tasks with greater cognitive load especially under the maximum length. Supplementary Information: The online version contains supplementary material available at 10.1007/s13534-023-00315-6.

Syntactic complexity differentially affects auditory sentence comprehension performance for individuals with age-related hearing loss.

Objectives: This study examined whether older adults with hearing loss (HL) experience greater difficulties in auditory sentence comprehension compared to those with typical-hearing (TH) when the linguistic burdens of syntactic complexity were systematically manipulated by varying either the sentence type (active vs. passive) or sentence length (3- vs. 4-phrases). Methods: A total of 22 individuals with HL and 24 controls participated in the study, completing sentence comprehension test (SCT), standardized memory assessments, and pure-tone audiometry tests. Generalized linear mixed effects models were employed to compare the effects of sentence type and length on SCT accuracy, while Pearson correlation coefficients were conducted to explore the relationships between SCT accuracy and other factors. Additionally, stepwise regression analyses were employed to identify memory-related predictors of sentence comprehension ability. Results: Older adults with HL exhibited poorer performance on passive sentences than on active sentences compared to controls, while the sentence length was controlled. Greater difficulties on passive sentences were linked to working memory capacity, emerging as the most significant predictor for the comprehension of passive sentences among participants with HL. Conclusion: Our findings contribute to the understanding of the linguistic-cognitive deficits linked to age-related hearing loss by demonstrating its detrimental impact on the processing of passive sentences. Cognitively healthy adults with hearing difficulties may face challenges in comprehending syntactically more complex sentences that require higher computational demands, particularly in working memory allocation.

Discourse-based verbal working memory training and transfer effects for individuals with an amnestic type of mild cognitive impairment.

PURPOSE: The purpose of the study was to investigate the treatment efficacy of a discourse-based working memory (WM) protocol for individuals with the amnestic type of mild cognitive impairment (MCI). METHOD: The current study employed a randomised, single-blind design. Fourteen individuals with MCI participated in the study (n = 7 treatment group and n = 7 control group). The treatment protocol consisted of 10 sessions two times per week, and treatment was individually administered only to the treatment group. A Wilcoxon signed-rank test was performed to verify pre-post comparisons within each group. Mann-Whitney nonparametric tests were conducted to confirm the differences between the treatment and control groups for the post-treatment scores. RESULT: The treatment group demonstrated a significant increase in story-retelling outcomes for both the treated stories and untreated novel stories compared to the control group. Furthermore, the treatment group presented transfer effects for WM span measures and controlled word association tasks. CONCLUSION: The results indicated that a discourse-based WM treatment protocol is efficacious for the amnestic type of mild cognitive impairment with the effects transferred to frontal lobe functions, as measured by WM tasks and semantic word fluency measures. Further studies are needed to track the trajectory of performance across sessions.

Effects of cochlear implantation on cognitive decline in older adults: A systematic review and meta-analysis.

Background: Hearing loss has been reported as the most significant modifiable risk factor for dementia, but it is still unknown whether auditory rehabilitation can practically prevent cognitive decline. We aim to systematically analyze the longitudinal effects of auditory rehabilitation via cochlear implants (CIs). Methods: In this systematic review and meta-analysis, we searched relevant literature published from January 1, 2000 to April 30, 2022, using electronic databases, and selected studies in which CIs were performed mainly on older adults and follow-up assessments were conducted in both domains: speech perception and cognitive function. A random-effects meta-analysis was conducted for each domain and for each timepoint comparison (pre-CI vs. six months post-CI; six months post-CI vs. 12 months post-CI; pre-CI vs. 12 months post-CI), and heterogeneity was assessed using Cochran's Q test. Findings: Of the 1918 retrieved articles, 20 research papers (648 CI subjects) were included. The results demonstrated that speech perception was rapidly enhanced after CI, whereas cognitive function had different speeds of improvement for different subtypes: executive function steadily improved significantly up to 12 months post-CI (g = 0.281, p < 0.001; g = 0.115, p = 0.003; g = 0.260, p < 0.001 in the order of timepoint comparison); verbal memory was significantly enhanced at six months post-CI and was maintained until 12 months post-CI (g = 0.296, p = 0.002; g = 0.095, p = 0.427; g = 0.401, p < 0.001); non-verbal memory showed no considerable progress at six months post-CI, but significant improvement at 12 months post-CI (g = -0.053, p = 0.723; g = 0.112, p = 0.089; g = 0.214, p = 0.023). Interpretation: The outcomes demonstrate that auditory rehabilitation via CIs could have a long-term positive impact on cognitive abilities. Given that older adults' cognitive abilities are on the trajectory of progressive decline with age, these results highlight the need to increase the adoption of CIs among this population.

What Eye Movement Reveals Concerning Age-Related Dissociation in Syntactic Prediction: Evidence From a Verb-Final Language.

PURPOSE: How older adults engage in predictive processing compared to young adults during sentence processing has been a controversial issue in psycholinguistic research. This study investigated whether age-related differences in predictive processing emerge and how they influence young and older adults' construction of sentential representations in a verb-final language using the visual world eye-tracking paradigm. METHOD: Twenty-five young adults and 24 older adults participated in this study. They were administered a sentence-picture matching task under active and passive conditions during which their eye movements were recorded. RESULTS: Older adults showed a stronger reliance on predictive processing based on probabilistic constraints compared to young adults at the second noun phrase (NP2) for both active and passive sentences. Specifically, older adults showed significantly greater target advantage looks in actives but greater distractor advantage looks in passives before encountering the verb compared to young adults, revealing older adults' stronger preference for active sentence representations. This stronger predictive processing at the NP2 among older adults engendered greater reduction in fixation proportion on the target picture at the verb only under the passive condition, suggesting that older adults experienced greater difficulties with syntactic revision and integration in passives compared to young adults. CONCLUSION: The current findings support that older adults more strongly rely on predictive processing based on probabilistic constraints denoted by case markers when constructing sentential representation compared to young adults, and this processing pattern increases processing difficulties when their prediction is incongruent with linguistic input.

Phonological and semantic strategies in a letter fluency task for people with Alzheimer's disease.

Objectives: This study investigated whether employing a phonological or semantic strategy elicited a better performance on a letter fluency task for people with Alzheimer's disease (AD). Methods: Sixty participants with probable AD were extracted from the DementiaBank database. After applying exclusion criteria, 47 participants were included in the final analysis. We used phonological and semantic strategies to analyze participants' responses to the letter fluency task. The phonological strategy analysis was based on the number of switches and the mean cluster size, and the semantic strategy analysis was based on semantic relatedness, which quantified word-similarity change by adapting the concept of persistence length from analyses of DNA and protein structures. We employed Pearson correlation coefficients to determine whether any strategy indexes were significantly related to the number of correct responses and used stepwise multiple regression analyses to determine the best predictor. Results: Participants who relied on phonological strategy performed better on the letter fluency task. The number of correct responses was significantly positively correlated with phonological strategy but significantly negatively correlated with semantic strategy. The number of switches, mean cluster size, and semantic relatedness were all significant predictors, explaining 68.1% of the variance. Conclusion: Our results suggested that individuals with AD who engaged in phonological strategy performed better on the letter fluency task than those who relied on semantic strategy.

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.

Age and Education Effects on a Novel Syntactic Assessment Battery for Elderly Adults.

The purpose of this study was to delineate the properties of a novel syntactic assessment battery and to present descriptive data on normal elderly individuals. We administered the Syntactic Assessment Battery (hereinafter SAB) using a sentence-picture paradigm to 195 normal elderly adults in three age groups (60-69, 70-79, and 80-90) and five educational levels (No formal education, Elementary School Graduation, Middle School Graduation, High School Graduation, College Graduation and Above). A multiple linear regression model was applied to verify the age and education effects. A summary of results indicated that the SAB effectively detected age and education effects. People generally demonstrated worse performance as they aged but better performance as their educational levels increased. People with high school education and above generally demonstrated stronger performance on the test, although educational effects were not significantly different between elementary and middle school graduation groups. The current novel syntactic assessment battery can serve as a screening measure that sensitively detects age and education effects.

Ethanol induces persistent potentiation of 5-HT3 receptor-stimulated GABA release at synapses on rat hippocampal CA1 neurons.

Several studies have shown that ethanol (EtOH) can enhance the activity of GABAergic synapses via presynaptic mechanisms, including in hippocampal CA1 neurons. The serotonin type 3 receptor (5-HT3-R) has been implicated in the neural actions of ethanol (EtOH) and in modulation of GABA release from presynaptic terminals. In the present study, we investigated EtOH modulation of GABA release induced by 5-HT3-R activation using the mechanically isolated neuron/bouton preparation from the rat CA1 hippocampal subregion. EtOH application before and during exposure to the selective 5-HT3 receptor agonist, m-chlorophenylbiguanide (mCPBG) potentiated the mCPBG-induced increases in the peak frequency and charge transfer of spontaneous GABAergic inhibitory postsynaptic currents. Interestingly, the potentiation was maintained even after EtOH was removed from the preparation. A protein kinase A inhibitor reduced the magnitude of EtOH potentiation. Fluorescent Ca2+ imaging showed that Ca2+ transients in the presynaptic terminals increased during EtOH exposure. These findings indicate that EtOH produces long-lasting potentiation of 5-HT3-induced GABA release by modulating calcium levels, via a process involving cAMP-mediated signaling in presynaptic terminals.

Syntactic Complexity as a Linguistic Marker to Differentiate Mild Cognitive Impairment From Normal Aging.

Purpose In this study, we sought to identify critical linguistic markers that can differentiate sentence processing of individuals with mild cognitive impairment (MCI) from the sentence processing of normal-aging populations by manipulating sentences' linguistic complexity. We investigated whether passive sentences, as linguistically complex structures, can serve as linguistic markers that can contribute to diagnoses that distinguish MCI from normal aging. Method In total, 52 participants, including 26 adults with amnestic MCI and 26 cognitively unimpaired adults, participated in the study. All participants were native speakers of Korean. We administered the two subsets of active and passive conditions using a sentence-picture paradigm with semantically reversible sentences to both groups. Results A mixed-effects model using PROC NLMIXED demonstrated that the MCI group exhibited differentially greater difficulty in processing passive than active sentences compared to the normal-aging group. A logistic regression fitted with the PROC LOGISTIC model identified the sum of the passive sentences, with age and education effects as the best models to distinguish individuals with MCI from the normal-aging group. Conclusion Sentence comprehension deficits emerged in the MCI stage when the syntactic complexity was increased. Furthermore, a passive structure was the best predictor for efficiently distinguishing the MCI group from the normal-aging group. These results are clinically and theoretically important, given that linguistic complexity can serve as a critical behavioral marker in the detection of early symptoms associated with linguistic-cognitive decline.