Browsing by Author "Elvevåg, Brita"
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- ItemAutomated computerized analysis of speech in psychiatric disorders.(2014-03-25) Cohen, Alex S; Elvevåg, BritaDisturbances in communication are a hallmark feature of severe mental illnesses Recent technological advances have paved the way for objectifying communication using automated computerized semantic linguistic and acoustic analyses We review recent studies applying various computer based assessments to the natural language produced by adult patients with severe mental illness
- ItemCategory fluency, latent semantic analysis and schizophrenia: a candidate gene approach.(2014-05-29) Nicodemus, Kristin K; Elvevåg, Brita; Foltz, Peter W; Rosenstein, Mark; Diaz-Asper, Catherine; Weinberger, Daniel RCategory fluency is a widely used task that relies on multiple neurocognitive processes and is a sensitive assay of cortical dysfunction including in schizophrenia The test requires naming of as many words belonging to a certain category e g animals as possible within a short period of time The core metrics are the overall number of words produced and the number of errors namely non members generated for a target category We combine a computational linguistic approach with a candidate gene approach to examine the genetic architecture of this traditional fluency measure
- ItemA computational language approach to modeling prose recall in schizophrenia.(2014-05-29) Rosenstein, Mark; Diaz-Asper, Catherine; Foltz, Peter W; Elvevåg, BritaMany cortical disorders are associated with memory problems In schizophrenia verbal memory deficits are a hallmark feature However the exact nature of this deficit remains elusive Modeling aspects of language features used in memory recall have the potential to provide means for measuring these verbal processes We employ computational language approaches to assess time varying semantic and sequential properties of prose recall at various retrieval intervals immediate 30 min and 24 h later in patients with schizophrenia unaffected siblings and healthy unrelated control participants First we model the recall data to quantify the degradation of performance with increasing retrieval interval and the effect of diagnosis i e group membership on performance Next we model the human scoring of recall performance using an n gram language sequence technique and then with a semantic feature based on Latent Semantic Analysis These models show that automated analyses of the recalls can produce scores that accurately mimic human scoring The final analysis addresses the validity of this approach by ascertaining the ability to predict group membership from models built on the two classes of language features Taken individually the semantic feature is most predictive while a model combining the features improves accuracy of group membership prediction slightly above the semantic feature alone as well as over the human rating approach We discuss the implications for cognitive neuroscience of such a computational approach in exploring the mechanisms of prose recall
- ItemDeriving semantic structure from category fluency: clustering techniques and their pitfalls.(2014-05-29) Voorspoels, Wouter; Storms, Gert; Longenecker, Julia; Verheyen, Steven; Weinberger, Daniel R; Elvevåg, BritaAssessing verbal output in category fluency tasks provides a sensitive indicator of cortical dysfunction The most common metrics are the overall number of words produced and the number of errors Two main observations have been made about the structure of the output first that there is a temporal component to it with words being generated in spurts and second that the clustering pattern may reflect a search for meanings such that the clustering is attributable to the activation of a specific semantic field in memory A number of sophisticated approaches to examining the structure of this clustering have been developed and a core theme is that the similarity relations between category members will reveal the mental semantic structure of the category underlying an individual s responses which can then be visualized by a number of algorithms such as MDS hierarchical clustering ADDTREE ADCLUS or SVD Such approaches have been applied to a variety of neurological and psychiatric populations and the general conclusion has been that the clinical condition systematically distorts the semantic structure in the patients as compared to the healthy controls In the present paper we explore this approach to understanding semantic structure using category fluency data On the basis of a large pool of patients with schizophrenia n 204 and healthy control participants n 204 we find that the methods are problematic and unreliable to the extent that it is not possible to conclude that any putative difference reflects a systematic difference between the semantic representations in patients and controls Moreover taking into account the unreliability of the methods we find that the most probable conclusion to be made is that no difference in underlying semantic representation exists The consequences of these findings to understanding semantic structure and the use of category fluency data in cortical dysfunction are discussed
- ItemLanguage, computers and cognitive neuroscience.(2014-05-29) Garrard, Peter; Elvevåg, Brita
- ItemNeural correlates of the relationship between discourse coherence and sensory monitoring in schizophrenia.(2014-05-29) Tagamets, Malle A; Cortes, Carlos R; Griego, Jacqueline A; Elvevåg, BritaUnusual language use is a core feature of psychosis but the nature and significance of this are not understood In particular thought disorder in schizophrenia SZ is characterized by markedly bizarre speech but the cognitive components that contribute to this and the brain correlates of these components are unknown A number of studies have demonstrated language abnormalities in single word processing but few have examined speech in SZ at the discourse level This has been at least partly due to the difficulty in quantifying content of discourse Recently methods in computational linguistics have been found to be useful for detecting differences in semantic coherence during discourse between different clinical groups We build on this work by demonstrating how these methods can be combined with funtional magnetic resonance imaging fMRI in order to tease apart factors that underlie free discourse and its deviations and how they relate to brain activity Eleven volunteers with SZ and eleven controls participated in an interview during which they were asked to talk as much as they could about religious belief These same participants underwent fMRI during a word monitoring task during which modality of monitoring was manipulated by varying the congruence of auditory and visual stimuli Semantic coherence scores measured from free discourse were examined for their relationship to brain activations during fMRI In healthy controls regions associated with executive function were related to coherence In persons with SZ coherence was mainly related to auditory and visual regions depending on the modality of monitoring but superior middle temporal cortex related to coherence regardless of task These findings are consistent with existing evidence for a role of superior temporal cortex in thought disorder and demonstrate that computational measures of semantic content capture objective measures of coherence in speech that can be usefully related to underlying neurophysiological processes
- ItemWhat do we really know about blunted vocal affect and alogia? A meta-analysis of objective assessments.(2014-12-03) Cohen, Alex S; Mitchell, Kyle R; Elvevåg, BritaDeficits in nonverbal vocal expression e g blunted vocal affect alogia are a hallmark of schizophrenia and are a focus of the Research Domain Criteria initiative from the National Institute of Mental Health Results from studies using symptom rating scales suggest that these deficits are profound on the order of four to six standard deviations To complement this endeavor we conducted a meta analysis of studies employing objective analysis of natural speech in patients with schizophrenia and nonpsychiatric controls Thirteen studies collectively including 480 patients with schizophrenia and 326 nonpsychiatric controls were identified There was considerable variability across studies in which aspects of vocal communication were examined and in the magnitudes of deficit Overall speech production reflecting alogia was impaired at a large effects size level d 80 k 13 whereas speech variability reflecting blunted affect was much more modest d 36 k 2 Regarding the former this was largely driven by measures of pause behavior as opposed to other aspects of speech e g number of words utterances On the other hand ratings of negative symptoms across these studies suggested profound group differences d 3 54 k 4 These data suggest that only certain aspects of vocal expression are affected in schizophrenia and highlight major discrepancies between symptom rating and objective based measures The discussion centers on advancing objective analysis for understanding vocal expression in schizophrenia and for identifying and defining more homogenous patient subsets for study