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S Rabe-Hesketh

Publications and source records attributed to S Rabe-Hesketh.

16 recordsLinked to original sources
PubMed2000

Common and distinct neural substrates for pragmatic, semantic, and syntactic processing of spoken sentences: an fMRI study.

Extracting meaning from speech requires the use of pragmatic, semantic, and syntactic information. A central question is: Does the processing of these different types of linguistic information have common or distinct neuroanatomical substrates? We addressed this issue using functional magnetic resonance imaging (fMRI) to measure neural activity when subjects listened to spoken normal sentences contrasted with sentences that had either (A) pragmatical, (B) semantic (selection restriction), or (C) syntactic (subcategorical) violations sentences. All three contrasts revealed robust activation of the left-inferior-temporal/fusiform gyrus. Activity in this area was also observed in a combined analysis of all three experiments, suggesting that it was modulated by all three types of linguistic violation. Planned statistical comparisons between the three experiments revealed (1) a greater difference between conditions in activation of the left-superior-temporal gyrus for the pragmatic experiment than the semantic/syntactic experiments; (2) a greater difference between conditions in activation of the right-superior and middle-temporal gyrus in the semantic experiment than in the syntactic experiment; and (3) no regions activated to a greater degree in the syntactic experiment than in the semantic experiment. These data show that, while left- and right-superior-temporal regions may be differentially involved in processing pragmatic and lexico-semantic information within sentences, the left-inferior-temporal/fusiform gyrus is involved in processing all three types of linguistic information. We suggest that this region may play a key role in using pragmatic, semantic (selection restriction), and subcategorical information to construct a higher representation of meaning of sentences.

Brain↗
PubMed2000

Meta-analysis of regional brain volumes in schizophrenia.

OBJECTIVE: The authors' goal was to determine whether patients with schizophrenia differ from comparison subjects in regional brain volumes and whether these differences are similar in male and female subjects. METHOD: They conducted a systematic search for structural magnetic resonance imaging (MRI) studies of patients with schizophrenia that reported volume measurements of selected cortical, subcortical, and ventricular regions in relation to comparison groups. They carried out a meta-analysis of the volumes of these regions in the patients with schizophrenia and the comparison subjects using a random effects model; they also used random effects regression analysis to examine the influence of gender on effect sizes. RESULTS: Fifty-eight studies were identified as suitable for analysis; these studies included 1,588 independent patients with schizophrenia. Assuming a volume of 100% in the comparison group, they found that the mean cerebral volume of the subjects with schizophrenia was smaller (98%), but the mean total ventricular volume of the subjects with schizophrenia was greater (126%). Relative to the cerebral volume differences, the regional volumes of the subjects with schizophrenia were 94% in the left and right amygdala, 94% in the left and 95% in the right hippocampus/amygdala, and 93% in the left and 95% in the right parahippocampus. Relative to the global ventricular system differences, the largest differences in ventricular subdivisions were in the right and left body of the lateral ventricle, where the volumes of schizophrenic subjects were 116% and 116%, respectively. For most regions, effect size was not significantly related to gender. CONCLUSIONS: Regional structural differences in patients with schizophrenia include bilaterally reduced volume of medial temporal lobe structures. There is a need for greater integration of results from structural MRI studies to avoid redundant research activity.

Adult↗
PubMed1999

School performance in Finnish children and later development of schizophrenia: a population-based longitudinal study.

BACKGROUND: We examined whether children who are diagnosed as having schizophrenia in adulthood could be distinguished from their peers on performance in elementary school. METHODS: We used a case-control study design nested within a population-based birth cohort of all individuals born in Helsinki, Finland, between January 1, 1951, and December 31, 1960. Case ascertainment was from 3 national health care registers. Elementary school records were obtained for 400 children who were diagnosed as having schizophrenia in adulthood and for 408 controls. Results were analyzed for the 4 years of schooling (ages 7-11 years) that were common to all pupils. School subjects were entered into a principal components analysis and produced 3 factors: academic, nonacademic, and behavioral. These factors were compared between cases and controls after adjusting for sex and social group. Eligibility for high school and progression to high school were investigated among cases and controls. RESULTS: Cases performed significantly worse than controls only on the nonacademic factor (which loaded sports and handicrafts). There were no differences between the groups on the academic or behavioral factors, and there were no significant clinical correlates of factor scores. Cases were significantly less likely than controls to progress to high school, despite similar eligibility. CONCLUSIONS: Poor performance in sports and handicrafts during elementary school, which may indicate a motor coordination deficit, appears to be a risk factor for later schizophrenia. Poor academic performance in elementary school was not a risk factor for schizophrenia in this study. Lack of expected progression to high school among cases, despite good academic grades, provides evidence for deteriorating premorbid functional adjustment in schizophrenia.

Achievement↗
PubMed1999

Life events, ethnicity and perceptions of discrimination in patients with severe mental illness.

BACKGROUND: Whilst it is commonly believed that black and ethnic minority (B&EM) people living in the UK experience social disadvantage compared with the white British (WB) population, no study has specifically addressed this issue in patients with severe mental illness. We sought to test the hypothesis that B&EM patients experience more negative life events than their WB counterparts, and to examine the extent to which they attribute these events to discrimination. METHOD: Thirty-four WB, 78 African Caribbean (AC) and 35 other ethnic minority patients with psychotic illnesses, defined using Research Diagnostic Criteria, were asked to complete a Racial Life Event Questionnaire examining life events and perceptions of discrimination at baseline and 12 and 24 months later. RESULTS: African Caribbean patients experienced more 'Financial' life events across the study period, otherwise there were no significant differences between patient groups in number of life events experienced. The B&EM group collectively (n = 113), however, were significantly more likely than the WB group (n = 34) to attribute 'Assault', and 'Legal' life events to discrimination. The AC patient group were significantly more likely than the other two ethnic groups to attribute the 'Financial' and 'Health' life events they experienced to discrimination. The B&EM group was also significantly more likely, and particularly the AC patient group, to report that members of their own ethnic group are adversely affected by discrimination. Further analyses showed skin colour rather than ethnicity or nationality to be the major contributing factor to perception of discrimination; thus, the Irish (n = 11) had similar scores to the WB while Africans (n = 16) scored like the ACs. CONCLUSION: Our study shows that B&EM patients do not experience significantly more life events than WB patients; however, their perception of these events is clearly different, and significantly more often attributed to racism. It is reasonable to suppose that patients may be disinclined to utilise services they believe to be prejudiced against them on the basis of their skin colour, and service providers need to be aware of this in order to create health care services that B&EM patients feel confident to use.

Adult↗
PubMed1999

Global, voxel, and cluster tests, by theory and permutation, for a difference between two groups of structural MR images of the brain.

We describe almost entirely automated procedures for estimation of global, voxel, and cluster-level statistics to test the null hypothesis of zero neuroanatomical difference between two groups of structural magnetic resonance imaging (MRI) data. Theoretical distributions under the null hypothesis are available for 1) global tissue class volumes; 2) standardized linear model [analysis of variance (ANOVA and ANCOVA)] coefficients estimated at each voxel; and 3) an area of spatially connected clusters generated by applying an arbitrary threshold to a two-dimensional (2-D) map of normal statistics at voxel level. We describe novel methods for economically ascertaining probability distributions under the null hypothesis, with fewer assumptions, by permutation of the observed data. Nominal Type I error control by permutation testing is generally excellent; whereas theoretical distributions may be over conservative. Permutation has the additional advantage that it can be used to test any statistic of interest, such as the sum of suprathreshold voxel statistics in a cluster (or cluster mass), regardless of its theoretical tractability under the null hypothesis. These issues are illustrated by application to MRI data acquired from 18 adolescents with hyperkinetic disorder and 16 control subjects matched for age and gender.

Adolescent↗
PubMed1999

Cerebral blood flow velocity during neonatal seizures.

AIM: To determine if cerebral blood flow velocity increases during all types of neonatal seizure, and whether the effect is due solely to an increase in blood pressure, transmitted to the cerebral circulation when autoregulation is impaired. METHODS: Seizures were diagnosed in 11 high risk neonates using cotside 16 channel video-EEG polygraphy. EEG, cerebral blood flow velocity (CBFV) using transcranial Doppler ultrasound, and arterial blood pressure (ABP) measurements were made. At least two 5-10 minute epochs of simultaneous measurements were performed on each infant. These epochs were then reviewed to eliminate artefacts, and one minute data periods containing a clear seizure onset were created. Each period contained 20 seconds before the seizure. Data periods without seizures from the same infants were also analysed and compared with seizure periods. RESULTS: Four infants had purely electrographic seizures-without clinical manifestations. Six infants had electroclinical seizures. One infant displayed both seizure types. A random effects linear regression analysis was used to determine the effect of seizures on CBFV and ABP. A significant increase was found in mean CBFV in those periods containing seizures. The mean percentage change in velocity for all infants was 15.6%. Three infants showed a significant increase in mean ABP after seizures but the overall increase in ABP for all infants was not significant. CONCLUSION: Electroclinical and electrographic neonatal seizures produce an increase in CBFV. In some infants the increase is not associated with an increase in blood pressure. These preliminary results suggest that electrographic seizures are associated with disturbed cerebral metabolism. Treatment of neonatal seizures until electrographic seizure activity is abolished may improve outcome for these infants.

Blood Flow Velocity↗
PubMed1999

Methods for diagnosis and treatment of stimulus-correlated motion in generic brain activation studies using fMRI.

Movement-related effects in realigned fMRI timeseries can be corrected by regression on linear functions of estimated positional displacements of an individual subject's head during image acquisition. However, this entails biased (under)estimation of the experimental effect whenever subject motion is not independent of the experimental input function. Methods for diagnosing such stimulus-correlated motion (SCM) are illustrated by application to fMRI data acquired from 5 schizophrenics and 5 normal controls during periodic performance of a verbal fluency task. The schizophrenic group data were more severely affected by SCM than the control group data. Analysis of covariance (ANCOVA) was used, with a voxelwise measure of SCM as a covariate, to estimate between-group differences in power of periodic signal change while controlling for variability in SCM across groups. Failure to control for SCM in this way substantially exaggerated the number of voxels, apparently demonstrating a between-group difference in task response.

Adult↗
PubMed1998

Reviewing the reviews: the example of chronic fatigue syndrome.

OBJECTIVE: To test the hypothesis that the selection of literature in review articles is unsystematic and is influenced by the authors' discipline and country of residence. DATA SOURCES: Reviews in English published between 1980 and March 1996 in MEDLINE, EMBASE (BIDS), PSYCHLIT, and Current Contents were searched. STUDY SELECTION: Reviews of chronic fatigue syndrome (CFS) were selected. Articles explicitly concerned with a specialty aspect of CFS and unattributed, unreferenced, or insufficiently referenced articles were discarded. DATA EXTRACTION: Record of data sources in each review was noted as was the departmental specialty of the first author and his or her country of residence. The references cited in each index paper were tabulated by assigning them to 6 specialty categories, by article title, and by assigning them to 8 categories, by country of journal publication. DATA SYNTHESIS: Of 89 reviews, 3 (3.4%) reported on literature search and described search method. Authors from laboratory-based disciplines preferentially cited laboratory references, while psychiatry-based disciplines preferentially cited psychiatric literature (P = .01). A total of 71.6% of references cited by US authors were from US journals, while 54.9% of references cited by United Kingdom authors were published in United Kingdom journals (P = .001). CONCLUSION: Citation of the literature is influenced by review authors' discipline and nationality.

Authorship↗
PubMed1998

Does dysplasia cause anatomical dysconnectivity in schizophrenia?

Evidence is reviewed that dysplastic brain development in the second half of pregnancy predisposes to schizophrenia. We suggest that an important corollary of aberrant development at this stage of ontogenesis is abnormal afferentation of the cortical plate, and that this may be macroscopically measurable in terms of abnormal correlational structure in adult brain imaging data. This prediction is tested by analysis of multiple cortical volume measures on magnetic resonance imaging data acquired from 35 male right-handed schizophrenics and 35 matched controls. There are no significant differences between groups in global, intra-hemispheric or inter-hemispheric correlational structure; but schizophrenics are shown to have significantly reduced dependencies between frontal and temporal lobe volumes, and frontal and hippocampal volumes, in the left hemisphere. We conclude that anatomical dysconnectivity (between frontal and temporal cortex) in schizophrenia may be caused by dysplasia.

Adult↗
PubMed1998

Do antiarthritic drugs decrease the risk for cognitive decline? An analysis based on data from the MRC treatment trial of hypertension in older adults.

We ascertained nonsteroidal anti-inflammatory drug (NSAID) use in 2,651 participants in the UK MRC treatment trial of hypertension in older adults and measured change in cognitive function over the subsequent 54 months. There was a significant, although modest, association between change in the Paired Associate Learning Test score over time and NSAID use, which was modified by age. NSAID users showed less decline, with younger subjects seeming to benefit more than older. We found no relationship between NSAID use and time taken to complete the Trail Making Test and also no relationship between anti-indigestion drug use and either cognitive outcome. These analyses highlight the need for larger studies with prospective classification of NSAID use and adequate control of confounding, including exposure to other medications. A randomized controlled trial of NSAIDs, in those known to be at risk of cognitive decline or dementia, may be indicated in the future.

Adrenergic beta-Antagonists↗
PubMed1997

Generic brain activation mapping in functional magnetic resonance imaging: a nonparametric approach.

We report a novel method to identify brain regions generically activated by periodic experimental design in functional magnetic resonance imaging data. This involves: 1) registering each of N individual functional magnetic resonance imaging datasets in a standard space; 2) computing the median standardised power of response to the experimental design; 3) testing median standardised power at each voxel against its nonparametrically ascertained distribution under the null hypothesis of no experimental effect; and 4) constructing a generic brain activation map. The method is validated by analysis of 6 null images, acquired under conditions when the null hypothesis was known to be true; 8 images acquired during periodic auditory-verbal stimulation; and 6 images acquired during periodic performance of a covert verbal fluency task.

Acoustic Stimulation↗
PubMed1997

The analysis of functional magnetic resonance images.

Functional magnetic resonance imaging (fMRI) is a powerful technique for measuring brain activity associated with the performance of different mental tasks. We briefly describe this technique and the images it produces and review methods of analysis that have been applied to fMRI data. Throughout the paper, we illustrate various points on an fMRI dataset.

Brain Mapping↗
PubMed1996

Statistical methods of estimation and inference for functional MR image analysis.

Two questions arising in the analysis of functional magnetic resonance imaging (fMRI) data acquired during periodic sensory stimulation are: i) how to measure the experimentally determined effect in fMRI time series; and ii) how to decide whether an apparent effect is significant. Our approach is first to fit a time series regression model, including sine and cosine terms at the (fundamental) frequency of experimental stimulation, by pseudogeneralized least squares (PGLS) at each pixel of an image. Sinusoidal modeling takes account of locally variable hemodynamic delay and dispersion, and PGLS fitting corrects for residual or endogenous autocorrelation in fMRI time series, to yield best unbiased estimates of the amplitudes of the sine and cosine terms at fundamental frequency; from these parameters the authors derive estimates of experimentally determined power and its standard error. Randomization testing is then used to create inferential brain activation maps (BAMs) of pixels significantly activated by the experimental stimulus. The methods are illustrated by application to data acquired from normal human subjects during periodic visual and auditory stimulation.

Acoustic Stimulation↗
PubMed1996

Functional magnetic resonance image analysis of a large-scale neurocognitive network.

Many "higher-order" mental functions are subserved by large-scale neurocognitive networks comprising several spatially distributed and functionally specialized brain regions. We here report statistical and graphical methods of functional magnetic resonance imaging data analysis which can be used to elucidate the functional relationships (i.e., connectivity and distance) between elements of a neurocognitive network in a single subject. Data were acquired from a normal right-handed volunteer during periodic performance of a task which demanded visual and semantic processing of words and subvocalization of a decision about the meaning of each word. Major regional foci of activation were identified (by sinusoidal regression modeling and spatiotemporal randomization tests) in left extrastriate cortex, angular gyrus, supramarginal gyrus, superior and middle temporal gyri, lateral premotor cortex, and Broca's area. Principal component (PC) analysis was initially undertaken by singular value decomposition (SVD) of the "raw" time series observed at 170 activated voxels. This revealed a large functional distance (negative connectivity) between visual processing systems and all other brain regions in the space of the first PC. SVD of a matrix of fitted time series, and a matrix of six sinusoidal regression parameters estimated at each activated voxel, were developed as less noisy (more informative) alternatives to SVD of the "raw" data. Canonical variate analysis of denoised data was then used to clarify functional relationships between the major regional foci. Visual input analysis systems (extrastriate cortex and angular gyrus) were colocalized in the space of the first canonical variate (CV) and significantly separated from all other brain regions. Semantic analysis systems (supramarginal and temporal gyri) were colocalized and significantly separated in the space of the second CV from the subvocal output system (Broca's area). These results are provisionally interpreted in terms of underlying hemodynamic events and cognitive psychological theory.

Adult↗