Matthew A. Lambon Ralph's research while affiliated with MRC Cognition and Brain Sciences Unit and other places
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Publications (481)
Knowledge about the consequences of stroke on high-level vision comes primarily from single case studies of patients selected based on their behavioural profiles, typically patients with specific stroke syndromes like pure alexia or prosopagnosia. There are, however, no systematic, detailed, large-scale evaluations of the more typical clinical beha...
Verbal fluency is widely used as a clinical test, but its utility in differentiating between neurodegenerative dementias and progressive aphasias, and from healthy controls, remains unclear. We assessed whether various measures of fluency performance could differentiate between Alzheimer’s disease, behavioural variant of frontotemporal dementia, no...
Alzheimer's disease spans a heterogeneous collection of typical and atypical phenotypes. Posterior cortical atrophy represents one of the most striking examples, characterised by prominent impairment in visual and other posterior functions in contrast to typical, predominantly amnestic Alzheimer's disease. Whilst putative posterior cortical atrophy...
Running title: Impaired social behaviour in frontotemporal dementia Keywords: frontotemporal dementia, semantic dementia, social-semantic knowledge, social control, social behaviour, anterior temporal lobe, orbitofrontal cortex 2 Abbreviations: bvFTD = behavioural-variant frontotemporal dementia; SD = semantic dementia; ATL = anterior temporal lobe...
A key goal for cognitive neuroscience is to understand the neurocognitive systems that support semantic memory. Recent multivariate analyses of neuroimaging data have contributed greatly to this effort, but the rapid development of these novel approaches has made it difficult to track the diversity of findings and to understand how and why they som...
Two common clinical variants of frontotemporal dementia are the behavioural variant frontotemporal dementia presenting with behavioural and personality changes attributable to prefrontal atrophy, and semantic dementia displaying early semantic dysfunction primarily due to anterior temporal degeneration. Despite representing independent diagnostic e...
Cerebral achromatopsia is an acquired colour perception impairment caused by brain injury, and is generally considered to be rare. Both hemispheres are thought to contribute to colour perception, but most published cases have had bilateral or right hemisphere lesions. In contrast to congenital colour blindness that affects the discrimination betwee...
Primary progressive aphasia (PPA) is a group of neurodegenerative disorders featuring primary-language impairments and typically classified into three-variants: semantic, non-fluent and logopenic. Yet their language profiles significantly overlap. Language deficits can also occur in other frontotemporal dementias (FTD) like progressive supranuclear...
Focal brain damage caused by stroke can result in aphasia and advances in cognitive neuroscience suggest that impairment may be associated with network-level disorder rather than just circumscribed cortical damage. A number of studies have shown meaningful relationships between brain-behaviour using lesions; however only a handful of studies have i...
It is increasingly acknowledged that patients with aphasia following a left-hemisphere stroke often have difficulties in other cognitive domains. One of these domains is attention, the very fundamental ability to detect, select, and react to the abundance of stimuli present in the environment. Basic and more complex attentional functions are usuall...
Neuro-cognitive models of semantic memory have proposed that the ventral anterior temporal lobes (vATLs) encode a graded, distributed, and multidimensional semantic space—yet neuroimaging studies seeking brain regions that encode semantic structure rarely identify these areas. In computer simulations we show that this discrepancy may arise from lim...
The posterior lateral temporal cortex is implicated in many verbal, nonverbal, and social cognitive domains and processes. Yet without directly comparing these disparate domains, the region’s organization remains unclear; do distinct processes engage discrete subregions, or could different domains engage shared neural correlates and processes? Here...
Speech and language therapy can be an effective tool in improving language in post-stroke aphasia. Despite an increasing literature on the efficacy of language therapies, there is a dearth of evidence about the neurocognitive mechanisms that underpin language re-learning, including the mechanisms implicated in neurotypical learning. Neurotypical wo...
Semantic control is the capability to operate on meaningful representations, selectively focusing on certain aspects of meaning while purposefully ignoring other aspects based on one's behavioral aim. This ability is especially vital for comprehending figurative/am-biguous language. It remains unclear why and how regions involved in semantic contro...
Language comprehension involves the construction of complex mental representations, i.e., “event representations”, reflecting current events or situation models. The construction of these representations requires manipulation of both semantic and episodic content and has been widely associated with the functioning of the posterior medial network, a...
Objective: Verbal fluency is clinically widely used but its utility in differentiating between neurodegenerative dementias and progressive aphasias, and from healthy controls, remains unclear. We assessed whether the total number of words produced, their psycholinguistic properties, and production order effects could differentiate between Alzheimer...
Objective
Multi-assessment batteries are necessary for diagnosing and quantifying the multifaceted deficits observed post-stroke. Extensive batteries are thorough but impractically long for clinical settings or large-scale research studies. Clinically-targeted “shallow” batteries superficially cover a wide range of language skills relatively quickl...
Tractography is widely used in human studies of connectivity with respect to every brain region, function, and is explored developmentally, in adulthood, aging, and in disease. However, the core issue of how to systematically threshold, taking into account the inherent differences in connectivity values for different track lengths, and to do this i...
The logopenic variant of primary progressive aphasia is characterized by early deficits in language production and phonological short-term memory, attributed to left-lateralized temporoparietal, inferior parietal and posterior temporal neurodegeneration. Despite patients primarily complaining of language difficulties, emerging evidence points to pe...
Patients with semantic aphasia have impaired control of semantic retrieval, often accompanied by executive dysfunction following left hemisphere stroke. Many but not all of these patients have damage to the left inferior frontal gyrus, important for semantic and cognitive control. Yet semantic and cognitive control networks are highly distributed,...
This study investigates the dynamics of speech envelope tracking during speech production, listening and self listening. We use a paradigm in which participants listen to natural speech (Listening), produce natural speech (Speech Production), and listen to the playback of their own speech (Self-Listening), all while their neural activity is recorde...
Semantic control allows us to focus semantic activation on currently relevant aspects of knowledge, even in the face of competition or when the required information is weakly encoded. Diverse cortical regions, including left prefrontal and posterior temporal cortex, are implicated in semantic control, however; the relative contribution of these reg...
Although impaired discourse production is one of the prominent features of aphasia, only a handful of investigations have addressed the cognitive, linguistic and neural processes that support the production of coherent discourse. In this study, we investigated the cognitive and neural correlates of discourse coherence in a large mixed cohort of pat...
Repetitive transcranial magnetic stimulation (rTMS) is a non-invasive technique used to modulate cortical excitability in the human brain. However, one major challenge with rTMS is that the responses to stimulation are highly variable across individuals. The underlying reasons why responses to rTMS are highly variable between individuals still rema...
Semantic cognition is a complex multifaceted brain function involving multiple processes including sensory, semantic, and domain-general cognitive systems. However, it remains unclear how these systems cooperate with each other to achieve effective semantic cognition. Here, we used independent component analysis (ICA) to investigate the functional...
Knowledge about the consequences of stroke on high level vision comes primarily from single case studies of patients selected based on their behavioural profiles with deficits in the recognition of a specific visual category such as faces or words. There are, however, no systematic, detailed, large-scale evaluations of the more typical clinical beh...
It is increasingly acknowledged that, often, patients with post-stroke aphasia not only have language impairments but also deficits in other cognitive domains (e.g. executive functions) that influence recovery and response to therapy. Many assessments of executive functions are verbally based and therefore usually not administered in this patient g...
Research of social neuroscience establishes that regions in the brain's default-mode network (DN) and semantic network (SN) are engaged by socio-cognitive tasks. Research of the human connectome shows that DN and SN regions are both situated at the transmodal end of a cortical gradient but differ in their loci along this gradient. Here we integrate...
A long history of neuropsychology and neuroimaging has implicated the angular gyrus (AG) with a myriad of cognitive functions. We investigated the functional engagement of AG by three forms of memory: 1) episodic/autobiographical memory 2) object semantic-memory, and 3) event-semantic processing using the previously under-examined naturalistic task...
Control processes are critical for the generation of task-appropriate behaviour across cognitive domains, yet children have a long developmental period with reduced executive control. Traditionally, this is viewed as a negative but necessary consequence of the time taken to learn control processes and develop the prefrontal cortex. Here, we exploit...
Background: Collation of aphasia research data across settings, countries and study designs using big data principles will support analyses across different language modalities, levels of impairment, and therapy interventions in this heterogeneous population. Big data approaches in aphasia research may support vital analyses, which are unachievable...
Cerebral achromatopsia is an acquired colour perception impairment caused by brain injury. Although we lack precise knowledge about prevalence, acquired colour perception deficits are considered to be rare. While both hemispheres contribute to colour perception, most published cases have had bilateral or right hemisphere lesions. In contrast to con...
Language is not a single function, but instead results from interactions between neural representations and computations that can be damaged independently of each other. Although there is now clear evidence that the language profile in post-stroke aphasia reflects graded variations along multiple underlying dimensions (‘components’), it is still en...
![Figure 4. Dosage (total speech and language therapy [SLT] hours) and...](profile/Louise-Williams-2/publication/356691652/figure/fig2/AS:1098222319738880@1638848013990/Dosage-total-speech-and-language-therapy-SLT-hours-and-associated-gains-from-baseline_Q320.jpg)
![Figure 4. Dosage (total speech and language therapy [SLT] hours) and...](profile/Louise-Williams-2/publication/356691652/figure/fig4/AS:1098469259378694@1638906888933/Dosage-total-speech-and-language-therapy-SLT-hours-and-associated-gains-from-baseline_Q320.jpg)
Background and Purpose
Optimizing speech and language therapy (SLT) regimens for maximal aphasia recovery is a clinical research priority. We examined associations between SLT intensity (hours/week), dosage (total hours), frequency (days/week), duration (weeks), delivery (face to face, computer supported, individual tailoring, and home practice), c...
The human dorsolateral prefrontal cortex (DLPFC, approximately corresponding to Brodmann areas 9 and 46) has demonstrable roles in diverse executive functions such as working memory, cognitive flexibility, planning, inhibition, and abstract reasoning. However, it remains unclear whether this is the result of one functionally homogeneous region or w...
Decades of research have highlighted the importance of lateral parietal cortex (LPC) across a myriad of cognitive domains. Yet, the underlying function of LPC remains unclear. Two domains that have emphasized LPC involvement are semantic memory and episodic memory retrieval. From each domain, sophisticated functional models have been proposed, as w...
New results from Popham et al. generate ‘semantic maps’ from spoken narratives and movies that appear remarkably aligned near visual cortex. We consider whether such findings are consistent with the hub-and-spokes view of semantic representation or whether they require a rethinking of the cortical knowledge system.
The posterior lateral temporal cortex is implicated in many verbal, nonverbal and social cognitive domains and processes. Yet without directly comparing these disparate domains, the region's organisation remains unclear; do distinct processes engage discrete subregions, or could different domains engage shared neural correlates and processes? Here,...
There are few available methods for qualitatively evaluating patients with primary progressive aphasia. Commonly adopted approaches are time-consuming, of limited accuracy, or designed to assess different patient populations. This paper introduces a new clinical test - the Mini Linguistic State Examination - which was designed uniquely to enable a...
The effect of repetitive transcranial magnetic stimulation can vary considerably across individuals, but the reasons for this still remain unclear. Here, we investigated whether the response to continuous theta-burst stimulation (cTBS) - an effective protocol for decreasing cortical excitability, is related to individual differences in glutamate an...
The Complementary Learning Systems (CLS) theory provides a powerful framework for considering the acquisition, consolidation, and generalization of new knowledge. We tested this proposed neural division of labor in adults through an investigation of the consolidation and long-term retention of newly learned native vocabulary with post-learning func...
Patients with semantic aphasia have impaired control of semantic retrieval, often accompanied by executive dysfunction following left hemisphere stroke. Many but not all of these patients have damage to the left inferior frontal gyrus, important for semantic and cognitive control. Yet semantic and cognitive control networks are highly distributed,...
The cerebrum comprises a set of specialised systems that tile across the cortical sheet, forming a tapestry-like configuration. For example, the multiple-demand and language-specific systems occupy largely separate neural estates and exhibit disparate functional profiles. Although delimiting the boundary between systems informs where cortical sheet...
Two common clinical variants of frontotemporal dementia (FTD) are the behavioural variant (bvFTD) presenting with behavioural and personality changes attributable to prefrontal atrophy, and semantic dementia (SD) displaying early semantic dysfunction primarily due to anterior temporal degeneration. Despite representing independent diagnostic entiti...
How does the human brain encode semantic information about objects? This paper reconciles two seemingly contradictory views. The first proposes that local neural populations independently encode semantic features; the second, that semantic representations arise as a dynamic distributed code that changes radically with stimulus processing. Combining...
Semantic diversity refers to the degree of semantic variability in the contexts in which a particular word is used. We have previously proposed a method for measuring semantic diversity based on latent semantic analysis (LSA). In a recent paper, Cevoli et al. (2020) attempted to replicate our method and obtained different semantic diversity values....
Although limited and reduced connected speech production is one, if not the most, prominent feature of aphasia, few studies have examined the properties of content words produced during discourse in aphasia, in comparison to the many investigations of single-word production. In this study, we used a distributional analysis approach to investigate t...
Fast periodic visual stimulation (FPVS) allows the recording of objective brain responses of human face categorization (i.e., generalizable face-selective responses) with high signal-to-noise ratio. This approach has been successfully employed in a number of scalp electroencephalography (EEG) studies but has not been used with magnetoencephalograph...
Semantic cognition is a complex brain function involving multiple processes from sensory systems, semantic systems, to domain-general cognitive systems, reflecting its multifaceted nature. However, it remain unclear how these systems cooperate with each other to achieve effective semantic cognition. Here, we investigated the neural networks involve...
Background : Progressive supranuclear palsy (PSP) and corticobasal syndrome (CBS) affect speech and language as well as motor functions. Clinical and neuropathological data indicate a close relationship between these two disorders and the non-fluent variant of primary progressive aphasia (nfvPPA). We use the recently developed Mini Linguistic State...
Recent evidence demonstrates that activation-dependent neuroplasticity on a structural level can occur in a short time (2 hour or less) in the human brain. However, the exact time scale of structural plasticity in the human brain remains unclear. Using voxel-based morphometry (VBM), we investigated changes in grey matter (GM) after one session of c...
Understanding the different neural networks that support human language is an ongoing challenge for cognitive neuroscience. Which divisions are capable of distinguishing the functional significance of regions across the language network? A key separation between semantic cognition and phonological processing was highlighted in early meta-analyses,...
Background: Despite the clinical importance of assessing the efficiency and accuracy of fluency in terms of content words production during connected speech, assessments based on discourse tasks are very time-consuming and thus not clinically feasible.
Aims (1) Examine the relationship between single-word naming and word retrieval during discourse...
The human dorsolateral prefrontal cortex (DLPFC, approximately corresponding to Brodmann areas 9 and 46) has demonstrable roles in diverse executive functions such as working memory, cognitive flexibility, planning, inhibition, and abstract reasoning. However, it remains unclear whether this is the result of one functionally homogeneous region or w...
The purpose of this study was to explore an important research goal in cognitive and clinical neuroscience: What are the neurocomputational mechanisms that make cognitive systems "well engineered" and thus resilient across a range of performance demands and to mild levels of perturbation or even damage? A new hypothesis called 'variable neuro-displ...
The flexible retrieval of knowledge is critical in everyday situations involving problem solving, reasoning and social interaction. Current theories emphasise the importance of a left-lateralised semantic control network (SCN) in supporting flexible semantic behaviour, while a bilateral multiple-demand network (MDN) is implicated in executive funct...
We employ a reverse-engineering approach to illuminate the neurocomputational building blocks that combine to support controlled semantic cognition: the storage and context-appropriate use of conceptual knowledge. By systematically varying the structure of a computational model and assessing the functional consequences, we identified the architectu...
Limb apraxia, a disorder of skilled action not consequent on primary motor or sensory deficits, has traditionally been defined according to errors patients make on neuropsychological tasks. Previous models of the disorder have failed to provide a unified account of patients’ deficits, due to heterogeneity in the patients and tasks used. In this stu...
Conceptual knowledge allows the categorisation of items according to their meaning beyond their physical similarities. This ability to respond to different stimuli (e.g., a leek, a cabbage, etc.) based on similar semantic representations (e.g., belonging to the vegetable category) is particularly important for language processing, because word mean...
Computational modelling has served as a powerful tool to advance our understanding of language processes by making theoretical ideas rigorously specified and testable (a form of 'open science' for theory building). In reading research, one of the most influential computational modelling frameworks is the triangle model of reading that characterises...
The Complementary Learning Systems (CLS) theory provides a powerful framework for considering the acquisition, consolidation and generalisation of new knowledge. We tested this proposed neural division of labour in adult humans through an investigation of the consolidation and long-term retention of newly learned native vocabulary. Over three weeks...
Rearch of social neuroscience establishes that regions in the brain's default network (DN) and semantic network (SN) are engaged by socio-cognitive tasks. Research of the human connectome shows that DN and SN regions are both situated at the high-order end of cortical gradient but differ in their positions on this gradient. In the present study, we...
Hyperscanning is an emerging technique that allows for the study of brain similarities between interacting individuals. This methodology has powerful implications for understanding the neural basis of joint actions, such as conversation; however, it also demands precise time-locking between the different brain recordings and sensory stimulation. Su...
