Showing papers by "Martha E. Shenton published in 1992"

Abnormalities of the left temporal lobe and thought disorder in schizophrenia. A quantitative magnetic resonance imaging study.

Abstract: Background. Data from postmortem, CT, and magnetic resonance imaging (MRI) studies indicate that patients with schizophrenia may have anatomical abnormalities of the left temporal lobe, but it is unclear whether these abnormalities are related to the thought disorder characteristic of schizophrenia. Methods. We used new MRI neuroimaging techniques to derive (without knowledge of the diagnosis) volume measurements and three-dimensional reconstructions of temporal-lobe structures in vivo in 15 right-handed men with chronic schizophrenia and 15 matched controls. Results. As compared with the controls, the patients had significant reductions in the volume of gray matter in the left anterior hippocampus—amygdala (by 19 percent [95 percent confidence interval, 3 to 36 percent]), the left parahippocampal gyrus (by 13 percent [95 percent confidence interval, 3 to 23 percent], vs. 8 percent on the right), and the left superior temporal gyrus (by 15 percent [95 percent confidence interval, 5 to 25 percent]...

Routine quantitative analysis of brain and cerebrospinal fluid spaces with MR imaging

Abstract: A computerized system for processing spin-echo magnetic resonance (MR) imaging data was implemented to estimate whole brain (gray and white matter) and cerebrospinal fluid volumes and to display three-dimensional surface reconstructions of specified tissue classes. The techniques were evaluated by assessing the radiometric variability of MR volume data and by comparing automated and manual procedures for measuring tissue volumes. Results showed (a) the homogeneity of the MR data and (b) that automated techniques were consistently superior to manual techniques. Both techniques, however, were affected by the complexity of the structure, with simpler structures (eg, the intracranial cavity) showing less variability and better spatial correlation of segmentation results between raters. Moreover, the automated techniques were completed for whole brain in a fraction of the time required to complete the equivalent segmentation manually. Additional evaluations included interrater reliability and an evaluation that included longitudinal measurement, in which one subject was imaged sequentially 24 times, with reliability computed from data collected by three raters over 1 year. Results showed good reliability for the automated segmentation procedures.

Unsupervised tissue type segmentation of 3D dual-echo MR head data

Abstract: The visualization of 3D phenomena and the extraction of quantitative information from magnetic resonance (MR) image data require efficient semiautomated or automated segmentation techniques. The application of multivariate statistical classification to the segmentation of dual-echo volume data of the human head into tissue types (grey matter, white matter and fluid spaces) is studied in this paper. Tests of the radiometric variability of tissue classes within the data volume demonstrate the improvement of the image acquisition technology and the suitability of statistical methods to perform brain tissue segmentation. Supervised classification is successfully applied to a study of 16 MR volume images of the human head, illustrating the robustness of this method in segmenting brain (white and grey matter) and cerebrospinal fluid (CSF). To avoid subjective criteria involved in the supervised approach, ISODATA clustering as well as clustering based on nonparametric probability density estimation were tested. Both methods performed well (success rates 93.8% and 87.5%, respectively), indicating that the classification procedure can be completely automated. The reproducibility and reliability of supervised and unsupervised classfication were studied by comparing results of segmentation performed by five expert operators. Results suggest that the interoperator and intraoperator variations could be reduced using automated clustering techniques. The accuracy of the volume calculations was quantified by applying the MR imaging and segmentation process to a phantom resembling shape and tissue characteristics of brain tissue. The segmented brain objects are displayed using 3D surface rendering.

Attentional cues in chronic schizophrenia : abnormal disengagement of attention

Abstract: Posner's (1980) reaction time (RT) paradigm was used to examine the engagement and disengagement operations of visual selective attention in patients with schizophrenia. In the 1st experiment, 14 medicated, chronic schizophrenic subjects (diagnosed by criteria of the Diagnostic and Statistical Manual of Mental Disorders', American Psychiatric Association, 1987) and 15 age-matched normal control subjects made a speeded response to a target preceded by a valid, an invalid, or no cue. Control subjects showed the expected advantage and disadvantage in RT for valid and invalid cues, which suggests intact engagement and disengagement operations. For schizophrenic patients, valid cues also enhanced RT, but invalid cues did not slow RT. Similar results were found in the 2nd experiment. The failure of unpredictable, invalid cues to inhibit RT in chronic schizophrenia may be related to an abnormality in the disengagement operation of selective attention.

In Vivo Occupancy of Dopamine Receptors by Antipsychotic Drugs-Reply

Abstract: In Reply.— We do not agree that the raters in the study by Berenbaum were able to distinguish normal subjects from schizophrenic patients on the thought disorder scale that Berenbaum used. Berenbaum was able to show differences between hospitalized schizophrenic twins and nonschizophrenic cotwins 1(p12) on three categories of thought disorder on the scale he used: "nonsequitur," "derailment," and "tangential responses." Only one of the nine categories of thought disorder (tangential responses) tested produced differences between nonhospitalized schizophrenic twins and the unaffected cotwins. 1 But one cannot re- gard the unaffected cotwins of schizophrenic patients as a normal control group. Indeed, there was no normal control group in that study, which Berenbaum et al also point out as a "limitation." 1 We previously noted, 2 in response to the initial letter by Berenbaum, 3 several other methodologic problems in his study. First, the thought disorder raters were minimally trained American undergraduate