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M E Shenton

Publications and source records attributed to M E Shenton.

90 records · Page 5Linked to original sources
PubMed1988

P300 in schizophrenia: confirmation and statistical validation of temporal region deficit in P300 topography.

Comparison of normal and medicated schizophrenic groups on the auditory P300 component of the event-related potential confirmed our earlier finding of a left temporal deficit in P300 amplitude in schizophrenia. A difference in P300 topography between groups was evident in both color mapping and in grand-averaged waveforms, which was statistically validated by the presence of a group-by-scalp region interaction (p less than 0.05). The left temporal area in schizophrenics was denoted as the region of greatest deficit and of maximal statistical separation (p less than 0.05) relative to normals by t statistic mapping (SPM), Hotelling's T-squared "protected" contrasts of individual scalp regions, and the relative ratio of left scalp amplitudes to right scalp amplitudes. The left temporal scalp region yielding maximal group separation in the previous study also statistically separated the schizophrenic group from the normal group. This feature correctly differentiated 9 of 11 schizophrenics and 7 of 9 controls. These findings are compatible with other histological, metabolic, and electrophysiological studies suggesting temporal lobe abnormality in schizophrenia.

Adult↗
PubMed1988

Patterns of thought disorder associated with right cortical damage, schizophrenia, and mania.

The authors used the Thought Disorder Index to measure thought disorder in 23 patients with unilateral right hemisphere cortical damage, 20 patients with bipolar mania, and 25 patients with schizophrenia. There were no differences in the total amount of thought disorder in these groups, but each showed a unique pattern of thought disorder. Patients with right hemisphere damage displayed fragmented thinking, manic patients displayed playful thinking, and schizophrenic patients displayed idiosyncratic thinking. These findings support the view that thought disorder is manifested in different forms that are relatively specific to psychiatric or neurological condition.

Adolescent↗
PubMed1988

Differentiation of schizophrenics and normal controls is enhanced by the Goodin subtraction procedure.

The P300 event-related potential as calculated by the Goodin subtraction procedure (P300g) combines attentive and inattentive condition waveforms in order to isolate components specifically related to target stimulus processing. The waveform was compared with the more commonly employed unsubtracted P300 waveform associated with attended infrequent stimuli (P300ia). The P300g produced the largest overall schizophrenic and control group differences in mean integrated amplitude compared with the P300ia. A group by scalp region interaction in the P300g, indicative of group topographic alterations, was also noted which was not present in the unsubtracted P300ia. Furthermore, the P300g pinpointed the single best scalp region (left temporal) for maximal group separation. This temporal asymmetry was found to originate in the inattentive condition waveforms, indicating a possible abnormality in "nonvoluntary" processing. We conclude that combining attentive and inattentive condition waveforms to form the P300g enhanced clinically relevant group differences between schizophrenics and normals compared with the P300ia.

Acoustic Stimulation↗
PubMed1987

Comparative studies of thought disorders. I. Mania and schizophrenia.

Thought disorder in 20 manic and 43 schizophrenic patients was examined using the Thought Disorder Index. To ensure the inclusion of patients with unambiguous mania and schizophrenia, the patients met Research Diagnostic Criteria, DSM-III criteria, and Washington University (St Louis) criteria. While the quantity of thought disorder did not differ significantly between the two groups, there were distinct qualitative differences. The thought disorder of manic patients was extravagantly combinatory, usually with humor, flippancy, and playfulness. The thought disorder of schizophrenic patients appeared disorganized, confused, and ideationally fluid, with many peculiar words and phrases.

Adult↗
PubMed1987

Comparative studies of thought disorders. II. Schizoaffective disorder.

We examined thought disorder in 22 patients with schizoaffective disorder (12 schizoaffective-manic and ten schizoaffective-depressed) using Research Diagnostic Criteria. The Thought Disorder Index was used to tag 22 categories of thought disorder that ranged from mild to severe. Qualitative patterns in the thought disorder of schizoaffective patients were compared with those of 20 manic and 43 schizophrenic patients. Manic and schizoaffective-manic patients produced a high number of combinatory responses, but those produced by the schizoaffective-manic patients lacked the humor and playfulness of those of the manics. The schizoaffective-manic patients, like the schizophrenic patients, produced a high number of responses in the categories of idiosyncratic verbalizations, autistic thinking, and confusion. Unlike the manic patients, schizoaffective-depressed patients generally produced a few absurd and idiosyncratic responses in a setting of constricted output. The data strongly suggest that the thinking disorders of schizoaffective patients are like those of the schizophrenic patients.

Adult↗
PubMed1986

Quality of thought disorder in differential diagnosis.

The authors used a reliable scale to assess quantity and quality of thought disorder in manic, schizophrenic, schizoaffective manic, and schizoaffective depressed patients. High levels of thought disorder occurred in all psychotic groups except in the schizoaffective depressed group. Manic patients produced thought disorders that revealed both prominent combinatory thinking and intrusions of irrelevant ideas into the stream of discourse, usually with flippancy and humor. The thinking of schizophrenic patients was confused and fluid, and usually peppered with many idiosyncratic and peculiar words and phrases. Although schizoaffective manic patients resembled manics in their tendency to show combinatory thinking, their productions lacked the jocularity of the manics. The schizoaffective manic patients more strongly resembled the schizophrenic patients in their production of idiosyncratic verbalizations and in confused thinking. Schizoaffective depressed patients showed a strikingly constricted output, but produced a few noteworthy absurd responses, and in that respect resembled the schizophrenic patients. The authors suggest that quality of thought disorder differs in schizophrenia and in mania, and that the thought disorder of schizoaffective conditions resembles that of schizophrenia.

Adult↗
PubMedDate not supplied

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

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.

Body Fluid Compartments↗
PubMedDate not supplied

The auditory N2 component in schizophrenia: relationship to MRI temporal lobe gray matter and to other ERP abnormalities.

The N2 component of the auditory event-related potential (ERP) indexes cognitive processes involved in the categorization of deviant stimuli. Although N2 amplitude and latency abnormalities have been reported in schizophrenia, their relationship to MRI structural changes, clinical status, and P3 abnormalities has not been defined. We therefore studied the auditory N2 and P3 components elicited by an oddball paradigm in 15 right-handed male subjects with schizophrenia and 14 control subjects who had quantitative MRI measures of temporal lobe gray-matter structures. To provide a methodological comparison, we measured the auditory N2 from both the target ERP (N2t) and the target-minus-frequent ERP difference (N2d) waveforms. Both N2t and N2d amplitude were bilaterally reduced in schizophrenics, with N2d showing a more pronounced reduction. Within the schizophrenic group, N2 amplitude reduction was associated with reduction in gray-matter volume of the left superior temporal gyrus (STG) and of medial temporal lobe structures bilaterally, and clinically, with greater chronicity. P3 amplitude, in contrast, correlated only with left posterior STG volume, and was more prominently associated with delusions and thought disorder. These findings suggest that the N2 and P3 components, though occurring sequentially in the ERP, tap separable anatomic and behavioral abnormalities in schizophrenia.

Adult↗
PubMedDate not supplied

Reversed temporal region asymmetries of P300 topography in left- and right-handed schizophrenic subjects.

The auditory P300 evoked potential was recorded in 36 subjects: left- (LH) and right-handed (RH) schizophrenic males and LH and RH normal controls. LH and RH normals showed no asymmetry in P300 scalp topography. LH and RH schizophrenics, however, showed lateralized asymmetries in temporal scalp regions: left < right P300 voltage asymmetry in RH schizophrenics and left > right P300 voltage asymmetry in LH schizophrenics. These data suggest that the schizophrenic pathology of P300 neural generators is lateralized according to handedness and provide the first evidence that LH and RH schizophrenics can be dissociated based on left-right voltage asymmetries in P300 topography. These findings further emphasize the need for control of handedness in P300 studies of schizophrenia.

Acoustic Stimulation↗
PubMedDate not supplied

P300 topographic asymmetries are present in unmedicated schizophrenics.

Our laboratory has repeatedly found a left < right auditory P300 temporal lobe topographic asymmetry in right-handed, medicated schizophrenics. To determine whether this asymmetry was attributable to the effects of antipsychotic medications, we collected auditory "odd-ball" P300 event-related potentials from 14 right-handed, unmedicated schizophrenics (withdrawn from medication for an average of 21 days) and 14 right-handed, normal controls. Analysis of normalized P300 amplitudes showed a statistically significant difference in the voltage distributions between groups (a group by temporal electrode site interaction) that was consistent with a left < right temporal voltage asymmetry in schizophrenics but not in the normal controls. We conclude that P300 topographic asymmetries are present in unmedicated schizophrenics. These data are compatible with the growing body of data suggesting left temporal lobe structural abnormalities in schizophrenia.

Acoustic Stimulation↗
PubMedDate not supplied

Measurement of visual sustained attention in schizophrenia using signal detection analysis and a newly developed computerized CPT task.

Sustained attention in schizophrenia was assessed with a newly developed, computer-controlled, modified version of the continuous performance test in which specific attentional effects can be empirically distinguished from nonspecific factors by signal detection theory (SDT). Results indicated that patients showed a more rapid decline in specific attentional, but not nonspecific processes, as measured by SDT parameters of A' and B", respectively.

Adult↗
PubMedDate not supplied

Event-related potentials in schizophrenia: their biological and clinical correlates and a new model of schizophrenic pathophysiology.

Evidence is growing that schizophrenic patients show significant structural damage in the temporal lobe limbic system. We review event-related potentials abnormalities (ERPs) in schizophrenia that may be related to dysfunction in this brain region or its inputs; ERPs discussed include the N100/P200, P300 and N400 components. Additional CT and clinical data have led our laboratory to a unifying working hypothesis of the presence of temporal lobe damage in schizophrenics that is evinced electrophysiologically as ERP alterations, structurally as tissue loss/derangement, and clinically as positive symptoms. The final section of this paper presents a new model of at least one form of schizophrenic pathology that, while speculative, incorporates experimentally based data from both our ERP work and from basic cellular physiology and pharmacology. The model proposes that positive symptoms of schizophrenia are related to limbic system pathology and in particular to a dysregulation of the NMDA form of excitatory amino acid transmission, potentiated by stress, and leading to cell damage and death due to 'excitotoxicity'.

Arousal↗
PubMedDate not supplied

Semantic disturbance in schizophrenia and its relationship to the cognitive neuroscience of attention.

We view schizophrenia as producing a failure of attentional modulation that leads to a breakdown in the selective enhancement or inhibition of semantic/lexical representations whose biological substrata are widely distributed across left (dominant) temporal and frontal lobes. Supporting behavioral evidence includes word recall studies that have pointed to a disturbance in connectivity (associative strength) but not network size (number of associates) in patients with schizophrenia. Paralleling these findings are recent neural network simulation studies of the abnormal connectivity effect in schizophrenia through 'lesioning' network connection weights while holding constant network size. Supporting evidence at the level of biology are in vitro studies examining N-methyl-D-aspartate (NMDA) receptor antagonists on recurrent inhibition; simulations in neural populations with realistically modeled biophysical properties show NMDA antagonists produce a schizophrenia-like disturbance in pattern association. We propose a similar failure of NMDA-mediated recurrent inhibition as a candidate biological substrate for attention and semantic anomalies of schizophrenia.

Attention↗
PubMedDate not supplied

Uniting Kraepelin and Bleuler: the psychology of schizophrenia and the biology of temporal lobe abnormalities.

Bleuler and Kraepelin are described as icons of the aggressively psychological and aggressively biologic approaches to schizophrenia. We suggest that methodologic advances in studying the function and structure of the brain now allow a reconciliation of these seemingly dissimilar approaches, particularly in the temporal lobe. We begin with a brief historic overview of these different approaches to schizophrenia and then describe structural (magnetic resonance imaging [MRI]), functional (event-related potential [ERP]), and neuropsychological studies in this disorder, including a summary of work conducted in our own laboratory. Recent MRI investigations agree on the presence of volume reductions in schizophrenia in the medial temporal lobe structures of the hippocampus-amygdala complex and of the para-hippocampal gyrus. Furthermore, two recent studies also indicate volume reductions in the superior temporal gyrus (STG). These volume reductions are most prominent in male patients and in the left hemisphere of right-handed patients with schizophrenia. Along with structural studies, there has been a burgeoning interest in MRI-clinical correlations, with volume reductions in the anterior STG being associated with hallucinations and those in the posterior STG being associated with thought disorder. Functional ERP studies also implicate the importance of the temporal lobe in schizophrenia; in addition, ERP abnormalities have been directly associated with a left greater than right MRI volume reduction of the posterior STG. Neuropsychological studies in nonpsychiatric patients are also consistent with a pattern of functional deficits shown to arise from temporal lobe abnormalities, whereas direct MRI-neuropsychological correlations in schizophrenic patients show that decreased performance on tests of verbal memory, abstraction, and categorization correlates with reduced MRI volume of left and right temporal lobe structures. Integration of these findings with those from basic neuroscience suggests a possible role of excitatory amino acid neurotransmission dysregulation and excitotoxicity in the pathology of schizophrenia. A data-based pathophysiologic characterization of schizophrenia is now becoming a reality, and the next few years should see a further unification of the Kraepelinian and Bleulerian approaches to this disorder.

Brain Mapping↗
PubMedDate not supplied

Temporal lobe abnormalities in a patient with schizophrenia who has word-finding difficulty: use of high-resolution magnetic resonance imaging and auditory P300 event-related potentials.

Postmortem, magnetic resonance, and event-related potential studies suggest the presence of temporal lobe abnormalities in schizophrenia. Analyses using convergent measurements of brain structure and function, however, have rarely been done in the same patients. We recently developed a protocol using high-spatial-resolution magnetic resonance scans, auditory P300 event-related potentials, and thought disorder scales to examine temporal lobe structure and function in the same patients. We report a case of schizophrenia that showed left-lateralized volume reduction in the superior temporal gyrus, hippocampus, and parahippocampal gyrus (also on right), with associated P300 amplitude reduction and thought disorder marked by word-finding difficulties and perseverations.

Anomia↗