Approaches to Measuring Language Lateralisation: An Exploratory Study Comparing Two fMRI Methods and Functional Transcranial Doppler Ultrasound.

In this exploratory study we compare and contrast two methods for deriving a laterality index (LI) from functional magnetic resonance imaging (fMRI) data: the weighted bootstrapped mean from the LI Toolbox (toolbox method), and a novel method that uses subtraction of activations from homologous regions in left and right hemispheres to give an array of difference scores (mirror method). Data came from 31 individuals who had been selected to include a high proportion of people with atypical laterality when tested with functional transcranial Doppler ultrasound (fTCD). On two tasks, word generation and semantic matching, the mirror method generally gave better agreement with fTCD laterality than the toolbox method, both for individual regions of interest, and for a large region corresponding to the middle cerebral artery.

Artificial intelligence-based decision support software to improve the efficacy of acute stroke pathway in the NHS: an observational study.

Introduction: In a drip-and-ship model for endovascular thrombectomy (EVT), early identification of large vessel occlusion (LVO) and timely referral to a comprehensive center (CSC) are crucial when patients are admitted to an acute stroke center (ASC). Several artificial intelligence (AI) decision-aid tools are increasingly being used to facilitate the rapid identification of LVO. This retrospective cohort study aimed to evaluate the impact of deploying e-Stroke AI decision support software in the hyperacute stroke pathway on process metrics and patient outcomes at an ASC in the United Kingdom.

Impact of e-ASPECTS software on the performance of physicians compared to a consensus ground truth: a multi-reader, multi-case study.

Background: The Alberta Stroke Program Early CT Score ASPECTS) is used to quantify the extent of injury to the brain following acute ischemic stroke (AIS) and to inform treatment decisions. The e-ASPECTS software uses artificial intelligence methods to automatically process non-contrast CT (NCCT) brain scans from patients with AIS affecting the middle cerebral artery (MCA) territory and generate an ASPECTS. This study aimed to evaluate the impact of e-ASPECTS (Brainomix, Oxford, UK) on the performance of US physicians compared to a consensus ground truth.

Generalized models for quantifying laterality using functional transcranial Doppler ultrasound.

We consider how analysis of brain lateralization using functional transcranial Doppler ultrasound (fTCD) data can be brought in line with modern statistical methods typically used in functional magnetic resonance imaging (fMRI). Conventionally, a laterality index is computed in fTCD from the difference between the averages of each hemisphere's signal within a period of interest (POI) over a series of trials. We demonstrate use of generalized linear models (GLMs) and generalized additive models (GAM) to analyze data from individual participants in three published studies (N = 154, 73 and 31), and compare this with results from the conventional POI averaging approach, and with laterality assessed using fMRI (N = 31).

Inconsistent language lateralisation - Testing the dissociable language laterality hypothesis using behaviour and lateralised cerebral blood flow.

Background: Most people have strong left-brain lateralisation for language, with a minority showing right- or bilateral language representation. On some receptive language tasks, however, lateralisation appears to be reduced or absent. This contrasting pattern raises the question of whether and how language laterality may fractionate within individuals.

Orthographic neighborhood effects during lateralized lexical decision are abolished with bilateral presentation.

Words presented to the right visual field (RVF) are processed more rapidly than those in the left visual field (LVF), presumably because of more direct links to the language dominant left cerebral hemisphere. This effect is moderated by a word's orthographic neighborhood size (N), with LVF facilitation and RVF inhibition for words with a large N. Across two experiments, we sought to further examine lateralized N effects.

Cerebral lateralisation of first and second languages in bilinguals assessed using functional transcranial Doppler ultrasound.

: Lateralised language processing is a well-established finding in monolinguals. In bilinguals, studies using fMRI have typically found substantial regional overlap between the two languages, though results may be influenced by factors such as proficiency, age of acquisition and exposure to the second language. Few studies have focused specifically on individual differences in brain lateralisation, and those that have suggested reduced lateralisation may characterise representation of the second language (L2) in some bilingual individuals.

The role of orthographic neighbourhood effects in lateralized lexical decision: a replication study and meta-analysis.

The effect of orthographic neighbourhood size (N) on lexical decision reaction time differs when words are presented in the left or right visual fields. Evidence suggests a facilitatory N effect (i.e.

An updated investigation of the multidimensional structure of language lateralization in left- and right-handed adults: a test-retest functional transcranial Doppler sonography study with six language tasks.

A previous study we reported in this journal suggested that left and right-handers may differ in their patterns of lateralization for different language tasks (Woodhead 2019 , 181801. (doi:10.1098/rsos.

Reading and alexia.

Alexia refers to a reading disorder caused by some form of acquired brain pathology, most commonly a stroke or tumor, in a previously literate subject. In neuropsychology, a distinction is made between central alexia (commonly seen in aphasia) and peripheral alexia (a perceptual or attentional deficit). The prototypical peripheral alexia is alexia without agraphia (pure alexia), where patients can write but are impaired in reading words and letters.

Investigating the effects of handedness on the consistency of lateralization for speech production and semantic processing tasks using functional transcranial Doppler sonography.

The left hemisphere is dominant for language in most people, but lateralization strength varies between different tasks and individuals. A large body of literature has shown that handedness is associated with lateralization: left handers have weaker language lateralization on average, and a greater incidence of atypical (right hemisphere) lateralization; but typically, these studies have relied on a single measure of language lateralization. Here we consider the relationships between lateralization for two different language tasks.

Assessing the reliability of an online behavioural laterality battery: A pre-registered study.

Studies of cerebral lateralization often involve participants completing a series of perceptual tasks under laboratory conditions. This has constrained the number of participants recruited in such studies. Online testing can allow for much larger sample sizes but limits the amount of experimental control that is feasible.

Measurement of language laterality using functional transcranial Doppler ultrasound: a comparison of different tasks.

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. Using fTCD, we evaluated a sentence generation task that has shown good reliability and strong left lateralisation in fMRI.

Testing the interhemispheric deficit theory of dyslexia using the visual half-field technique.

A deficit in interhemispheric transfer has been proposed as a neuropsychological theory of dyslexia. Interactions between the hemispheres during word recognition can be studied using the visual half-field paradigm. The well-established recognition advantage for right visual field (RVF) words over left visual field (LVF) words is thought to reflect the additional processing costs associated with callosal transfer of LVF word representations to the language-specialised left hemisphere.

Investigation into inconsistent lateralisation of language functions as a potential risk factor for language impairment.

Disruption to language lateralisation has been proposed as a cause of developmental language impairments. In this study, we tested the idea that consistency of lateralisation across different language functions is associated with language ability. A large sample of adults with variable language abilities (N = 67 with a developmental disorder affecting language and N = 37 controls) were recruited.

How Does iReadMore Therapy Change the Reading Network of Patients with Central Alexia?

Central alexia (CA) is an acquired reading disorder co-occurring with a generalized language deficit (aphasia). The roles of perilesional and ipsilesional tissue in recovery from poststroke aphasia are unclear. We investigated the impact of reading training (using iReadMore, a therapy app) on the connections within and between the right and left hemisphere of the reading network of patients with CA.

Testing the unitary theory of language lateralization using functional transcranial Doppler sonography in adults.

Hemispheric dominance for language can vary from task to task, but it is unclear if this reflects error of measurement or independent lateralization of different language systems. We used functional transcranial Doppler sonography to assess language lateralization within the middle cerebral artery territory in 37 adults (seven left-handers) on six tasks, each given on two occasions. Tasks taxed different aspects of language function.

Dorsal and ventral visual stream contributions to preserved reading ability in patients with central alexia.

We investigated the role of the left temporo-parietal regions in supporting reading abilities of 23 patients with central alexia (CA). For the behavioural data, we employed principal components analysis (PCA), which identified two components: 'reading aloud' and 'reading for meaning'. Voxel-based morphometry of the PCA results showed an association between reading aloud and grey matter density in the left supramarginal gyrus, part of the dorsal visual stream.

Randomized trial of iReadMore word reading training and brain stimulation in central alexia.

Central alexia is an acquired reading disorder co-occurring with a generalized language deficit (aphasia). We tested the impact of a novel training app, 'iReadMore', and anodal transcranial direct current stimulation of the left inferior frontal gyrus, on word reading ability in central alexia. The trial was registered at www.

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

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.

Methodological considerations in assessment of language lateralisation with fMRI: a systematic review.

The involvement of the right and left hemispheres in mediating language functions has been measured in a variety of ways over the centuries since the relative dominance of the left hemisphere was first known. Functional magnetic resonance imaging (fMRI) presents a useful non-invasive method of assessing lateralisation that is being increasingly used in clinical practice and research. However, the methods used in the fMRI laterality literature currently are highly variable, making systematic comparisons across studies difficult.

Auditory training changes temporal lobe connectivity in 'Wernicke's aphasia': a randomised trial.

Introduction: Aphasia is one of the most disabling sequelae after stroke, occurring in 25%-40% of stroke survivors. However, there remains a lack of good evidence for the efficacy or mechanisms of speech comprehension rehabilitation.

Trial Design: This within-subjects trial tested two concurrent interventions in 20 patients with chronic aphasia with speech comprehension impairment following left hemisphere stroke: (1) phonological training using 'Earobics' software and (2) a pharmacological intervention using donepezil, an acetylcholinesterase inhibitor.

Psychogenic and neural visual-cue response in PD dopamine dysregulation syndrome.

Introduction: Dopamine dysregulation syndrome (DDS) in Parkinson's disease (PD) patients refers to the compulsive use of dopaminergic replacement therapy and has serious psycho-social consequences. Mechanisms underlying DDS are not clear although has been linked to dysfunctional brain reward networks.

Methods: With fMRI, we investigate behavioral and neural response to drug-cues in six PD DDS patients and 12 PD control patients in both the ON and OFF medication state.