175 research outputs found
A semantic network dictionary for dysphasia therapy
With the use of computer-assisted teaching and learning programs the speech therapy of children with dysphasia can be planned more effectively, than with the traditional, so-called prompted-image method employed by logopaedists. Our aim is the creation of a semantic network dictionary - on the basis of a huge quantity empirical database -, which predicts what other concepts will link to a concept in the STM of 4—7 year old children, i.e. what other concepts can the most easily be associated with an already existing one by the therapeut. Furthermore, the semantic network dictionary will enable the already literate child - on the basis of the idea of András Kocsor - to take a virtual tour through the connected words of the network dictionary by merely saying words into a microphone. Hence the software will help children develop and maintain semantic structures
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Single-Route and Dual-Route Approaches to Reading Aloud Difficulties Associated with Dysphasia.
The study of reading aloud is currently informed by two main types of theory: modular dual-route and connectionist single-route. One difference between the
theories is the type of word classification system which they favour. Dual-route theory employs the regular-irregular dichotomy of classification, whereas single
route considers body neighbourhoods to be a more informative approach. This thesis explores the reading aloud performance of a group of people with dysphasia from the two theoretical standpoints by employing a specifically prepared set of real and pseudoword stimuli. As well as being classified according to regularity and body neighbourhood, all the real word stimuli were controlled for frequency. The pseudowords were divided into two groups, common pseudowords and pseudohomophones, and classified according to body neighbourhood. There were two main phases to the study. In the first phase, the stimuli were piloted and the response time performances of a group of people with dysphasia and a group of matched control people were compared. In the second phase, a series of tasks was developed to investigate which means of word classification best explained the visual lexical decision and reading aloud performance of people with dysphasia. The influence of word knowledge was also considered. The data was analysed both quantitatively and qualitatively. The quantitative analysis of the number of errors made indicated that classification of items by body neighbourhood and frequency provided the more comprehensive explanation of the data. Investigation of the types of errors that were made did not find a significant
relationship between word type and error type, but again the results indicated that the influence of frequency and body neighbourhood was stronger than that of regularity. The findings are discussed both in terms of their implications for the two theories of reading aloud and their relevance to clinical practice
Repetition-imitation and aphasia: Neural Basis and treatment
Study 2: a single-case study was developed. Repetition performance was widely assessed in a patient with crossed conduction aphasia and striatal/capsular vascular lesions encompassing the right arcuate fasciculus (AF) and inferior frontal-occipital fasciculus (IFOF), the temporal stem and the white matter underneath the supramarginal gyrus. He showed lexicality effects repeating better words than non-words, but manipulation of other lexical-semantic variables exerted less influence on repetition performance. Imageability and frequency effects, production of meaning-based paraphrases during sentence repetition, or better performance on repeating novel sentences than overlearned clichés were hardly ever observed in this patient. Diffusion tensor imaging disclosed damage to the right long direct segment of the AF and IFOF with relative sparing of the anterior indirect and posterior segments of the AF, together with fully developed left perisylvian white matter pathways. These findings suggest that striatal/capsular lesions extending into the right AF and IFOF in some individuals with right hemisphere language dominance are associated with atypical repetition patterns which might reflect reduced interactions between phonological and lexical-semantic processes.
Study 3: A within-patient design, with multiple assessments, was developed with the same patient as in Study 2A. The initial dose of Donepezil (5 mg/day) was titulated up to 10 mg/day and administered alone (without aphasia therapy) during 3 months (Endpoint 1). Then, the drug was combined with a verbal repetition-imitation therapy (Look-Listen and Repeat - LLR) (1 hour/day) during 2 months (Endpoint 2). Language evaluations, diffusion tensor imaging (DTI) and voxel-based morphometry (VBM) were performed at baseline and at both endpoints. Donepezil alone and combined with LLR induced marked improvement in measures of speech production (Correct Information Units/minute during picture description, and repetition of word lists, idiomatic-novel phrases and sentences). Greater benefits were observed after combined therapy and the obtained gains in speech production remained well-above baseline scores even four months after combined therapy interruption. Longitudinal DTI showed structural plasticity in the right frontal aslant tract (FAT) with both interventions and VBM additionally revealed increased grey matter density in cortical areas connected through the FAT. Donepezil alone and combined with LLR improved speech production deficits by inducing structural plastic changes in white matter tracts and grey matter areas spared by the lesion in the injured hemisphere. Conclusions: Cholinergic modulation and intensive verbal repetition-imitation therapy improve speech production deficits in crossed conduction aphasia by inducing right hemisphere structural plasticity.
Conclusions: MSRT become a simultaneous training of attention, auditory and visual input processing with the activation of different semantic fields, STM, executive processing, and language production. Treatment with donepezil has a positive effect in communication skills of CA patient. We observe a summative effect between donepezil and MSRT. The improvement associates neuroplasticity changes in neuroimaging.In the past two decades, single-case studies evaluated the effect of massed repetition training to improve speech production and short-term memory deficits in conduction aphasia (CA). Improvements were reported in treated language and memory domains with modest generalisation of gains to spontaneous speech or auditory comprehension. Although these results are encouraging, sentence repetition training has not been compared with distributed speech-language therapy, and no studies have examined the role of pharmacological interventions to enhance gains promoted by these behavioural interventions in CA. To explore repetition and imitation in the context of neural basis and treatment of aphasia, we developed three studies (STUDY 1, 2 & 3).
Study 1:
The effects of massed sentence repetition therapy (MSRT) were compared to those of distributed speech-language therapy (DSLT) in measures of verbal output, short-term memory and repetition in patients with chronic post-stroke CA receiving treatment with the cholinesterase inhibitor donepezil (DP). Both interventions improved performance in speech production tasks, but better improvements were found with DP-MSRT than with DP-DSLT. Larger treatment effects were found for DP-MSRT in comparison with baselines and DP-DSLT in repetition of word pairs and triplets, and novel and experimental sentences with generalisation of gains to aphasia severity, connected speech and non-treated control sentences
Contributions of memory circuits to language: The declarative/procedural model
The structure of the brain and the nature of evolution suggest that, despite its uniqueness, language likely depends on brain systems that also subserve other functions. The declarative/procedural (DP) model claims that the mental lexicon of memorized word-specific knowledge depends on the largely temporal-lobe substrates of declarative memory, which underlies the storage and use of knowledge of facts and events. The mental grammar, which subserves the rule-governed combination of lexical items into complex representations, depends on a distinct neural system. This system, which is composed of a network of specific frontal, basal-ganglia, parietal and cerebellar structures, underlies procedural memory, which supports the learning and execution of motor and cognitive skills, especially those involving sequences. The functions of the two brain systems, together with their anatomical, physiological and biochemical substrates, lead to specific claims and predictions regarding their roles in language. These predictions are compared with those of other neurocognitive models of language. Empirical evidence is presented from neuroimaging studies of normal language processing, and from developmental and adult-onset disorders. It is argued that this evidence supports the DP model. It is additionally proposed that "language" disorders, such as specific language impairment and non-fluent and fluent aphasia, may be profitably viewed as impairments primarily affecting one or the other brain system. Overall, the data suggest a new neurocognitive framework for the study of lexicon and grammar
Augmentative communication device design, implementation and evaluation
The ultimate aim of this thesis was to design and implement an advanced software based Augmentative Communication Device (ACD) , or Voice Output Communication Aid NOCA), for non-vocal Learning Disabled individuals by applying current psychological models, theories, and experimental techniques. By taking account of potential user's cognitive and linguistic abilities a symbol based device (Easy Speaker) was produced which outputs naturalistic digitised human speech and sound and makes use of a photorealistic symbol set. In order to increase the size of the available symbol set a hypermedia style dynamic screen approach was employed. The relevance of the hypermedia metaphor in relation to models of knowledge representation and language processing was explored.Laboratory based studies suggested that potential user's could learn to productively operate the software, became faster and more efficient over time when performing set conversational tasks. Studies with unimpaired individuals supported the notion that digitised speech was less cognitively demanding to decode, or listen to.With highly portable, touch based, PC compatible systems beginning to appear it is hoped that the otherwise silent will be able to use the software as their primary means of communication with the speaking world. Extensive field trials over a six month period with a prototype device and in collaboration with user's caregivers strongly suggested this might be the case.Off-device improvements were also noted suggesting that Easy Speaker, or similar software has the potential to be used as a communication training tool. Such training would be likely 10 improve overall communicative effectiveness.To conclude, a model for successful ACD development was proposed
Neural substrate of emotion in man : a study in methodology
Emotional behaviour has several components, which include
emotional perception, emotional expression, autonomic reactivity, and inner
subjective experience. It is hypothesised that these different processes can be
selectively disturbed after brain damage. However, emotional and cognitive
deficits usually co-exist in a particular patient, and the relationship between
cognition and emotion is discussed.
Animal data indicate that, following an initial sensory analysis in
primary and association cortex, a stimulus acquires emotional significance by
interfacing with "limbic" processes through multimodal cortex. Emotional
expressions also develop in the course of similar multistage integrations
between motor and limbic processes. This suggests three possible relationships
between cognitive and emotional deficit. First, an inability to either perceive or
express emotion may be directly due to various primary "non-emotional"
perceptuo-motor deficits. Secondly, damage to neural sites where limbic and
sensori-motor systems interface may produce deficits which are
simultaneously cognitive and emotional. For example, perseverative behaviour
in the Wisconsin Card Sorting Test and inability to control emotional impulses
may be different aspects of a single deficit, which is indissociably cognitive and
emotional. Thirdly, there may be a class of "pure" emotional deficits, which are
not associated with perceptuo-motor or cognitive deficit.
Tests based on the above classification approach were used to
assess the effect of lesion site on emotional functioning. Cognitive function,
emotional perception, emotional expression, subjective response, and
autonomic reactivity were assessed in 48 patients with focal brain lesions, and
10 matched non-brain injured controls. Patients with anterior lesions were
impaired relative to posteriors and controls in emotional perception and
expression. These frontal deficits remained after statistical control of lesion
variables (size, aetiology, and degree of bilateral involvement), and
non-emotional perceptual, motor or cognitive impairments. Though such
statistical controls provide suggestive evidence of a specific emotional deficit,
they cannot completely eliminate the possibility that the frontal deficit is
secondary to perceptuo-motor or cognitive impairment. Experimental
strategies designed to provide more positive evidence of a specific emotional
disorder were employed, and met with partial success.
Dysphasia affected performance on tests of emotional perception
and expression after left brain damage. Following right hemisphere damage,
visual perceptual deficit contributed to impairment in emotional perception.
There were indications that hemispheric perceptual-cognitive asymmetries may
not account for all right-left differences on the emotional subtests. However no
current model of hemispheric emotional asymmetries could fully explain the
present findings. For example, the data on emotional perception supported the
view that the right hemisphere is specialised for attentional/emotional
processes (Heilman et al, 1983), but neglect and emotional expression were not
correlated. Also, the present data generally contradicted the hypothesis that
positive and negative emotions are lateralised in the left and right hemispheres,
respectively.
The final chapter assesses the extent to which the data fit the
proposed system for categorising emotional disorder. Limitations to the
methods used in making this evaluation were discussed, and possible ways of
overcoming these restrictions were briefly considered
The Value of Seizure Semiology in Epilepsy Surgery: Epileptogenic-Zone Localisation in Presurgical Patients using Machine Learning and Semiology Visualisation Tool
Background
Eight million individuals have focal drug resistant epilepsy worldwide. If their epileptogenic focus is identified and resected, they may become seizure-free and experience significant improvements in quality of life. However, seizure-freedom occurs in less than half of surgical resections.
Seizure semiology - the signs and symptoms during a seizure - along with brain imaging and electroencephalography (EEG) are amongst the mainstays of seizure localisation. Although there have been advances in algorithmic identification of abnormalities on EEG and imaging, semiological analysis has remained more subjective.
The primary objective of this research was to investigate the localising value of clinician-identified semiology, and secondarily to improve personalised prognostication for epilepsy surgery.
Methods
I data mined retrospective hospital records to link semiology to outcomes. I trained machine learning models to predict temporal lobe epilepsy (TLE) and determine the value of semiology compared to a benchmark of hippocampal sclerosis (HS).
Due to the hospital dataset being relatively small, we also collected data from a systematic review of the literature to curate an open-access Semio2Brain database. We built the Semiology-to-Brain Visualisation Tool (SVT) on this database and retrospectively validated SVT in two separate groups of randomly selected patients and individuals with frontal lobe epilepsy.
Separately, a systematic review of multimodal prognostic features of epilepsy surgery was undertaken.
The concept of a semiological connectome was devised and compared to structural connectivity to investigate probabilistic propagation and semiology generation.
Results
Although a (non-chronological) list of patients’ semiologies did not improve localisation beyond the initial semiology, the list of semiology added value when combined with an imaging feature. The absolute added value of semiology in a support vector classifier in diagnosing TLE, compared to HS, was 25%. Semiology was however unable to predict postsurgical outcomes. To help future prognostic models, a list of essential multimodal prognostic features for epilepsy surgery were extracted from meta-analyses and a structural causal model proposed.
Semio2Brain consists of over 13000 semiological datapoints from 4643 patients across 309 studies and uniquely enabled a Bayesian approach to localisation to mitigate TLE publication bias. SVT performed well in a retrospective validation, matching the best expert clinician’s localisation scores and exceeding them for lateralisation, and showed modest value in localisation in individuals with frontal lobe epilepsy (FLE).
There was a significant correlation between the number of connecting fibres between brain regions and the seizure semiologies that can arise from these regions.
Conclusions
Semiology is valuable in localisation, but multimodal concordance is more valuable and highly prognostic. SVT could be suitable for use in multimodal models to predict the seizure focus
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Inner speech in post-stroke aphasia : a behavioural and imaging study
Patients with aphasia often complain that there is a poor correlation between the words they think (inner speech) and the words they say (overt speech). Previous studies show that there are some cases in which inner speech is preserved while overt speech is impaired, and vice versa. However, these studies have various methodological and theoretical drawbacks. In cognitive models of language processing, inner speech is described as either dependent on both speech production and speech comprehension, or on the speech production system alone. Lastly, imaging studies show that inner speech is correlated with activation in various language areas. However, these studies are sparse and many have methodological caveats. Moreover, studies looking at inner speech in stroke patients are rare.
This study examined inner speech in post-stroke aphasia using three different methodological approaches. Using cognitive behavioural methods, inner speech was characterised in healthy participants and stroke patients with aphasia. Using imaging, the brain structures which support inner speech were investigated. Two different methods were employed in this instance: Voxel based Lesion Symptom Mapping (VLSM) and Voxel Based Morphometry (VBM). Lastly, functional magnetic resonance imaging (fMRI) was used to study the dynamics of functional activations supporting inner speech production.
The study showed that inner speech can remain intact while there is a marked deficit in overt speech. Structural studies suggested an involvement of the dorsal language route in inner speech processing, together with systems supporting motor feedback and executive functions. Functional imaging showed that inner speech processing in stroke is correlated with compensatory peri-lesional and contra-lesional activations. Activations outside the language network might reflect increase in effort or attention, or the use of feed forward and feedback mechanisms to support inner speech production. These results have implications for diagnosis, prognosis and therapy of certain patients with post-stroke aphasia
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