Spoken discourse in episodic autobiographical and verbal short-term memory in Chinese people with dementia: the roles of global coherence and informativeness

Introduction

Memory and discourse production are closely related in healthy populations. A few studies in people with amnestic mild cognitive impairment and people with dementia (PWD) suggested similar links, although empirical evidence is insufficient to inform emerging intervention design and natural language processing research. Fine-grained discourse assessment is needed to understand their complex relationship in PWD.

Methods

Spoken samples from 104 PWD were elicited using personal narrative and sequential picture description and assessed using Main Concept Analysis and other content-based analytic methods. Discourse and memory performance data were analyzed in bivariate correlation and linear multiple regression models to determine the relationship between discourse production and episodic autobiographical memory and verbal short-term memory (vSTM).

Results

Global coherence was a significant predictor of episodic autobiographical memory, explaining over half of the variance. Both episodic autobiographical memory and vSTM were positively correlated with global coherence and informativeness, and negatively with empty speech indices.

Discussion

Coherence in personal narrative may be supported by episodic autobiographical memory and vice versa, suggesting potential mechanism of interventions targeting personhood through conversation. Indices of global coherence, informativeness, and empty speech can be used as markers of memory functions in PWD.

Assessment of inference-making in children using comprehension questions and story retelling: Effect of text modality and a story presentation format

BACKGROUND

Reading and listening comprehension are essential for accessing the school curriculum. Inference-making is integral to successful comprehension and involves integrating information between clauses (local coherence) and integrating information with background knowledge (global coherence). We require appropriate methods to assess comprehension and inference-making in order to identify areas of difficulty and provide appropriate support.

AIMS

Typically developing children's ability to generate local and global coherence inferences was assessed. The effect of text modality (reading and listening comprehension) and presentation format (stories presented in segmented and whole story format) was explored using two comprehension measures (question answering and story retell). The main aims were to determine whether there were advantages for reading or listening comprehension and for segmented or whole text presentation.

METHODS & PROCEDURES

Typically developing children in Year 3 (n = 33) and Year 5 (n = 40) either read or listened to short stories. Their ability to generate global and local coherence inferences was assessed in two ways: answers to inference-tapping questions and story retelling (scored for inclusion of necessary inferences). Stories were presented in either a whole format (all questions after the story) or a segmented format (questions asked at specific points during story presentation); the retelling was always after the complete story and questions had been presented.

OUTCOMES & RESULTS

For both comprehension measures, there was developmental progression between age groups and a benefit for the reading modality. Scores were higher for global coherence than local coherence inferences, but the effect was significant only for the question-answering responses, not retells. For retells there was a benefit in presenting the text as a whole compared with the segmented format, but this effect was not present for the comprehension questions. There was a significant interaction between inference type and modality for both comprehension measures (question answering and story retell): for the local coherence inferences scores were significantly greater in the reading compared with the listening modality, but performance on the global coherence inferences did not differ significantly between modalities.

CONCLUSIONS & IMPLICATIONS

Clinicians, teachers and other professionals should consider the modality and presentation format for comprehension tasks to utilize areas of strength and support areas of difficulty. Oral presentation may result in poorer comprehension relative to written presentation in general, and may particularly affect local integrative processing. These findings have important implications for the development of appropriate assessments as well as for supporting children with comprehension difficulties. What this paper adds What is already known on the subject Reading and listening comprehension are critical for accessing the school curriculum and educational success. Inference-making is integral to successful comprehension and involves integrating information between clauses (local coherence) as well as integrating information with background knowledge (global coherence). Children have an awareness of the need to generate coherence inferences, but not all children will generate sufficient coherence inferences for adequate comprehension during text presentation. Existing assessment tools measure comprehension by asking questions after story presentation. This provides an overall indication of comprehension or inference-making ability and can identify children with comprehension or language and communication difficulties. What this paper adds to existing knowledge The study compared coherence inference-making in two presentation conditions: whole format (all questions after the story) or segmented format (questions asked at specific points during story presentation). Children (aged 7-10 years) were assessed in the reading or listening modality. Two comprehension measures were used (inference-tapping questions and story retell). There was developmental progression and a benefit for the reading modality for both comprehension measures. Scores were higher for global coherence than local coherence inferences for the comprehension questions. There was a benefit in presenting the text as a whole compared with the segmented format for story retells. What are the potential or actual clinical implications of this work? The results are important for clinicians and other professionals assessing and supporting comprehension skills. The results suggest that the modality and presentation format of comprehension tasks should be considered to utilize areas of strength and support areas of difficulty. The optimum form of input and structure may depend on a child's individual profile and the skill being assessed or supported. Targeted questions may identify a child's potential to generate an inference. This may assist identification of children who may require more targeted or specialist intervention. The reading modality may provide a means of support for development of verbal comprehension.

Biophysical mechanisms governing large-scale brain network dynamics underlying individual-specific variability of perception

Perception necessitates interaction among neuronal ensembles, the dynamics of which can be conceptualized as the emergent behavior of coupled dynamical systems. Here, we propose a detailed neurobiologically realistic model that captures the neural mechanisms of inter-individual variability observed in cross-modal speech perception. From raw EEG signals recorded from human participants when they were presented with speech vocalizations of McGurk-incongruent and congruent audio-visual (AV) stimuli, we computed the global coherence metric to capture the neural variability of large-scale networks. We identified that participants' McGurk susceptibility was negatively correlated to their alpha band global coherence. The proposed biophysical model conceptualized the global coherence dynamics emerge from coupling between the interacting neural masses-representing the sensory-specific auditory/visual areas and modality nonspecific associative/integrative regions. Subsequently, we could predict that an extremely weak direct AV coupling results in a decrease in alpha band global coherence-mimicking the cortical dynamics of participants with higher McGurk susceptibility. Source connectivity analysis also showed decreased connectivity between sensory-specific regions in participants more susceptible to McGurk effect, thus establishing an empirical validation to the prediction. Overall, our study provides an outline to link variability in structural and functional connectivity metrics to variability of performance that can be useful for several perception and action task paradigms.

Augmenting EEG-global-coherence with auditory and visual noise: Multisensory internal stochastic resonance

The present investigation documents the electrophysiological occurrence of multisensory internal stochastic resonance (MISR) in the human electroencephalographic (EEG) coherence elicited by auditory and visual noise.We define MISR of EEG coherence as the phenomenon for which an intermediate level of input noise of a sensory modality enhances EEG coherence in response to another noisy sensory modality. Here, EEG coherence is computed by the global weighted coherence (GWC), modulated by quasi-Brownian noise. Specifically, we examined whether a particular level of auditory noise together with constant visual noise (experimental condition 1) and a specified level of visual noise together with constant auditory noise (experimental condition 2), improves EEG's GWC. We compared GWC between ongoing EEG basal activity (BA), zero noise (ZN), optimal noise (ON), and high noise (HN).The data disclosed an intermediate level of input noise that enhances the GWC for the majority of the subjects, thus demonstrating for the first time the occurrence of multisensory internal stochastic resonance (SR) in visuoauditory processing within the central nervous system.

Time and Narrative: An Investigation of Storytelling Abilities in Children With Autism Spectrum Disorder

This study analyzed the relation between mental time travel (MTT) and the ability to produce a storytelling focusing on global coherence, which is one of the most notable characteristics of narrative discourse. As global coherence is strictly tied to the temporal sequence of the events narrated in a story, we hypothesized that the construction of coherent narratives would rely on the ability to mentally navigate in time. To test such a hypothesis, we investigated the relation between one component of MTT—namely, episodic future thinking (EFT)—and narrative production skills by comparing the narratives uttered by 66 children with high-functioning autism spectrum disorder (ASD) with those produced by 66 children with typical development. EFT was assessed by administering a task with minimal narrative demands, whereas storytelling production skills were assessed by administering two narrative production tasks that required children to generate future or past episodes with respect to the target stimuli. The results showed that EFT skills were impaired only in a subgroup of children with ASD and that such subgroup performed significantly worse on the narrative production task than ASD participants with high EFT skills and participants with typical development. The practical and theoretical implications of these findings are discussed.

The Impact of Age and Cognitive Reserve on Resting-State Brain Connectivity

Cognitive reserve (CR) is a protective mechanism that supports sustained cognitive function following damage to the physical brain associated with age, injury, or disease. The goal of the research was to identify relationships between age, CR, and brain connectivity. A sample of 90 cognitively normal adults, ages 45–64 years, had their resting-state brain activity recorded with electroencephalography (EEG) and completed a series of memory and executive function assessments. CR was estimated using years of education and verbal IQ scores. Participants were divided into younger and older age groups and low- and high-CR groups. We observed greater left- than right-hemisphere coherence in younger participants, and greater right- than left-hemisphere coherence in older participants. In addition, greater coherence was observed under eyes-closed than eyes-open recording conditions for both low-CR and high-CR participants, with a more substantial difference between recording conditions in individuals high in CR regardless of age. Finally, younger participants low in CR exhibited greater mean coherence than younger participants high in CR, whereas the opposite pattern was observed in older participants, with greater coherence in older participants high in CR. Together, these findings suggest the possibility of a shift in the relationship between CR and brain connectivity during aging.

Assessing school-aged children's inference-making: the effect of story test format in listening comprehension

BACKGROUND

Comprehension is critical for classroom learning and educational success. Inferences are integral to good comprehension: successful comprehension requires the listener to generate local coherence inferences, which involve integrating information between clauses, and global coherence inferences, which involve integrating textual information with background knowledge to infer motivations, themes, etc. A central priority for the diagnosis of comprehension difficulties and our understanding of why these difficulties arise is the development of valid assessment instruments.

AIMS

We explored typically developing children's ability to make local and global coherence inferences using a novel assessment of listening comprehension. The aims were to determine whether children were more likely to make the target inferences when these were asked during story presentation versus after presentation of the story, and whether there were any age differences between conditions.

METHODS & PROCEDURES

Children in Years 3 (n = 29) and 5 (n = 31) listened to short stories presented either in a segmented format, in which questions to assess local and global coherence inferences were asked at specific points during story presentation, or in a whole format, when all the questions were asked after the story had been presented.

OUTCOMES & RESULTS

There was developmental progression between age groups for both types of inference question. Children also scored higher on the global coherence inference questions than the local coherence inference questions. There was a benefit of the segmented format for younger children, particularly for the local inference questions.

CONCLUSIONS & IMPLICATIONS

The results suggest that children are more likely to make target inferences if prompted during presentation of the story, and that this format is particularly facilitative for younger children and for local coherence inferences. This has implications for the design of comprehension assessments as well as for supporting children with comprehension difficulties in the classroom.

The Social Brain Is Not Enough: On the Importance of the Ecological Brain for the Origin of Language

In this paper, I assume that the study of the origin of language is strictly connected to the analysis of the traits that distinguish human language from animal communication. Usually, human language is said to be unique in the animal kingdom because it enables and/or requires intentionality or mindreading. By emphasizing the importance of mindreading, the social brain hypothesis has provided major insights within the origin of language debate. However, as studies on non-human primates have demonstrated that intentional forms of communication are already present in these species to a greater or lesser extent, I maintain that the social brain is a necessary but not a sufficient condition to explain the uniqueness of language. In this paper, I suggest that the distinctive feature of human communication resides in the ability to tell stories, and that the origin of language should be traced with respect to the capacity to produce discourses, rather than phrases or words. As narrative requires the ability to link events distant from one another in space and time, my proposal is that in order to explain the origin of language, we need to appeal to both the social brain and the ecological brain - that is, the cognitive devices which allow us to mentally travel in space and time.

Global coherence during discourse production in adults: a review of the literature

BACKGROUND

Global coherence is a metric of expressive language performance that represents the speaker's ability to initiate, plan and maintain a topic of discussion. Studies indicate that disruptions of global coherence can occur during the ageing process and following neurological disease or injury. However, little is known about the specific impact that the ageing process, disease or injury has on global coherence during discourse production.

AIMS

To review the literature on global coherence in adult populations and assess the impact that age, disease or injury has on global coherence during expressive language tasks.

METHODS & PROCEDURES

We completed an in-depth search of Medline and PyschInfo (1990-2014) to identify studies of global coherence in adult populations. We identified studies that included a comparison group and utilized a measure of global coherence during expressive language production among adults.

OUTCOMES & RESULTS

Twenty studies comprised of 692 study participants who met inclusion criteria were identified for the review of the literature. Studies included participants without neurological impairments and individuals with aphasia, traumatic brain injury, dementia, generalized memory impairment and other neurological conditions. Study results indicated global coherence is an expressive language skill that is influenced by the ageing process and neurological disease or injury.

CONCLUSIONS & IMPLICATIONS

Although evidence indicated that global coherence is negatively influenced by ageing and neurological disease/injury, the heterogeneity of study populations, measurement tools and study designs were limiting factors in determining the exact nature by which these factors impact the skill of global coherence.