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Measuring language lateralisation with different language tasks: a systematic review.

ABSTRACT: Language lateralisation refers to the phenomenon in which one hemisphere (typically the left) shows greater involvement in language functions than the other. Measurement of laterality is of interest both to researchers investigating the neural organisation of the language system and to clinicians needing to establish an individual's hemispheric dominance for language prior to surgery, as in patients with intractable epilepsy. Recently, there has been increasing awareness of the possibility that different language processes may develop hemispheric lateralisation independently, and to varying degrees. However, it is not always clear whether differences in laterality across language tasks with fMRI are reflective of meaningful variation in hemispheric lateralisation, or simply of trivial methodological differences between paradigms. This systematic review aims to assess different language tasks in terms of the strength, reliability and robustness of the laterality measurements they yield with fMRI, to look at variability that is both dependent and independent of aspects of study design, such as the baseline task, region of interest, and modality of the stimuli. Recommendations are made that can be used to guide task design; however, this review predominantly highlights that the current high level of methodological variability in language paradigms prevents conclusions as to how different language functions may lateralise independently. We conclude with suggestions for future research using tasks that engage distinct aspects of language functioning, whilst being closely matched on non-linguistic aspects of task design (e.g., stimuli, task timings etc); such research could produce more reliable and conclusive insights into language lateralisation. This systematic review was registered as a protocol on Open Science Framework: https://osf.io/5vmpt/.

SUBMITTER: Bradshaw AR

PROVIDER: S-EPMC5659218 | biostudies-literature | 2017

REPOSITORIES: biostudies-literature

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Measuring language lateralisation with different language tasks: a systematic review.

Bradshaw Abigail R AR Thompson Paul A PA Wilson Alexander C AC Bishop Dorothy V M DVM Woodhead Zoe V J ZVJ

PeerJ 20171024

Language lateralisation refers to the phenomenon in which one hemisphere (typically the left) shows greater involvement in language functions than the other. Measurement of laterality is of interest both to researchers investigating the neural organisation of the language system and to clinicians needing to establish an individual's hemispheric dominance for language prior to surgery, as in patients with intractable epilepsy. Recently, there has been increasing awareness of the possibility that ...[more]

PMID: 29085748

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Project description:Background: Relative blood flow in the two middle cerebral arteries can be measured using functional transcranial Doppler sonography (fTCD) to give an index of lateralisation as participants perform a specific task. Language laterality has mostly been studied with fTCD using a word generation task, but it is not clear whether this is optimal. Methods: Using fTCD, we evaluated a sentence generation task that has shown good reliability and strong left lateralisation in fMRI. We interleaved trials of word generation, sentence generation and list generation and assessed agreement of these tasks in 31 participants (29 right-handers). Results: Although word generation and sentence generation both gave robust left-lateralisation, lateralisation was significantly stronger for sentence generation. Bland-Altman analysis showed that these two methods were not equivalent. The comparison list generation task was not systematically lateralised, but nevertheless laterality indices (LIs) from this task were significantly correlated with the other two tasks. Subtracting list generation LI from sentence generation LI did not affect the strength of the laterality index. Conclusions: This was a pre-registered methodological study designed to explore novel approaches to optimising measurement of language lateralisation using fTCD. It confirmed that sentence generation gives robust left lateralisation in most people, but is not equivalent to the classic word generation task. Although list generation does not show left-lateralisation at the group level, the LI on this task was correlated with left-lateralised tasks. This suggests that word and sentence generation involve adding a constant directional bias to an underlying continuum of laterality that is reliable in individuals but not biased in either direction. In future research we suggest that consistency of laterality across tasks might have more functional significance than strength or direction of laterality on any one task.

Project description:Language tasks require the coordinated activation of multiple subnetworks-groups of related cortical interactions involved in specific components of task processing. Although electrocorticography (ECoG) has sufficient temporal and spatial resolution to capture the dynamics of event-related interactions between cortical sites, it is difficult to decompose these complex spatiotemporal patterns into functionally discrete subnetworks without explicit knowledge of each subnetwork's timing. We hypothesized that subnetworks corresponding to distinct components of task-related processing could be identified as groups of interactions with co-varying strengths. In this study, five subjects implanted with ECoG grids over language areas performed word repetition and picture naming. We estimated the interaction strength between each pair of electrodes during each task using a time-varying dynamic Bayesian network (tvDBN) model constructed from the power of high gamma (70-110Hz) activity, a surrogate for population firing rates. We then reduced the dimensionality of this model using principal component analysis (PCA) to identify groups of interactions with co-varying strengths, which we term functional network components (FNCs). This data-driven technique estimates both the weight of each interaction's contribution to a particular subnetwork, and the temporal profile of each subnetwork's activation during the task. We found FNCs with temporal and anatomical features consistent with articulatory preparation in both tasks, and with auditory and visual processing in the word repetition and picture naming tasks, respectively. These FNCs were highly consistent between subjects with similar electrode placement, and were robust enough to be characterized in single trials. Furthermore, the interaction patterns uncovered by FNC analysis correlated well with recent literature suggesting important functional-anatomical distinctions between processing external and self-produced speech. Our results demonstrate that subnetwork decomposition of event-related cortical interactions is a powerful paradigm for interpreting the rich dynamics of large-scale, distributed cortical networks during human cognitive tasks.

Project description:Policy Points: Investigations on systematic methodologies for measuring integrated care should coincide with the growing interest in this field of research. A systematic review of instruments provides insights into integrated care measurement, including setting the research agenda for validating available instruments and informing the decision to develop new ones. This study is the first systematic review of instruments measuring integrated care with an evidence synthesis of the measurement properties. We found 209 index instruments measuring different constructs related to integrated care; the strength of evidence on the adequacy of the majority of their measurement properties remained largely unassessed.Integrated care is an important strategy for increasing health system performance. Despite its growing significance, detailed evidence on the measurement properties of integrated care instruments remains vague and limited. Our systematic review aims to provide evidence on the state of the art in measuring integrated care.Our comprehensive systematic review framework builds on the Rainbow Model for Integrated Care (RMIC). We searched MEDLINE/PubMed for published articles on the measurement properties of instruments measuring integrated care and identified eligible articles using a standard set of selection criteria. We assessed the methodological quality of every validation study reported using the COSMIN checklist and extracted data on study and instrument characteristics. We also evaluated the measurement properties of each examined instrument per validation study and provided a best evidence synthesis on the adequacy of measurement properties of the index instruments.From the 300 eligible articles, we assessed the methodological quality of 379 validation studies from which we identified 209 index instruments measuring integrated care constructs. The majority of studies reported on instruments measuring constructs related to care integration (33%) and patient-centered care (49%); fewer studies measured care continuity/comprehensive care (15%) and care coordination/case management (3%). We mapped 84% of the measured constructs to the clinical integration domain of the RMIC, with fewer constructs related to the domains of professional (3.7%), organizational (3.4%), and functional (0.5%) integration. Only 8% of the instruments were mapped to a combination of domains; none were mapped exclusively to the system or normative integration domains. The majority of instruments were administered to either patients (60%) or health care providers (20%). Of the measurement properties, responsiveness (4%), measurement error (7%), and criterion (12%) and cross-cultural validity (14%) were less commonly reported. We found <50% of the validation studies to be of good or excellent quality for any of the measurement properties. Only a minority of index instruments showed strong evidence of positive findings for internal consistency (15%), content validity (19%), and structural validity (7%); with moderate evidence of positive findings for internal consistency (14%) and construct validity (14%).Our results suggest that the quality of measurement properties of instruments measuring integrated care is in need of improvement with the less-studied constructs and domains to become part of newly developed instruments.

Dataset Information

Measuring language lateralisation with different language tasks: a systematic review.

Publications

Measuring language lateralisation with different language tasks: a systematic review.

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