ABSTRACT Background / Purpose: The cingulum bundle is the major white matter tract connecting the... more ABSTRACT Background / Purpose: The cingulum bundle is the major white matter tract connecting the cortex and limbic system, and is involved in memory, reasoning and emotion. It has been observed to be abnormal in patients with chronic schizophrenia (Kubicki et al 2007), but it has been less studied in first episode (FE).18 patients with FE schizophrenia, 20 patients with chronic schizophrenia (CSZ) and 20 controls were matched to each patient group (FENC and CSZNC), and received diffusion imaging on a 3T GE MRI. Two regions of interest, anterior and posterior portions of the cingulum bundle, were manually placed for each subject to initiate streamlined tractography. After successful fiber tracking, mean trace (TR), fractional anisotropy (FA), axial and radial diffusivity (AD and RD) were calculated for each subject. Main conclusion: FE exhibited higher TR in comparison to FENC in both hemispheres and on the left in comparison to CSZ. AD was increased in the FE bilaterally in comparison to FENC and CSZ. RD was higher in FE compared to FENC bilaterally and was correlated with delusions of reference.These results suggest that both axial and radial diffusivity contribute to the change in overall white matter health and organization between first episode and chronic schizophrenia, reflecting abnormalities in both axon integrity and myelination. In particular anomalies in myelin integrity may be related to the severity of delusions of reference. This is consistent with abnormal myelin development that results in partial degeneration of the underlying axons.
Seeking to unite psychological and biological approaches, this paper links cognitive and cellular... more Seeking to unite psychological and biological approaches, this paper links cognitive and cellular hypotheses and data about thought and language abnormalities in schizophrenia. The common thread, it is proposed, is a dysregulated suppression of associations (at the behavioral and functional neural systems level), paralleled by abnormalities of inhibition at the cellular and molecular level, and by an abnormal anatomical substrate (reduced MRI gray matter volume) in areas subserving language. At the level of behavioral experiments and connectionist modeling, data suggest an abnormal semantic network connectivity (strength of associations) in schizophrenia, but not an abnormality of network size (number of associates). This connectivity abnormality is likely to be a preferential processing of the dominant (strongest) association, with the neglect of preceding contextual information. At the level of functional neural systems, the N400 event-related potential amplitude is used to index ...
Despite its potential for visualizing white matter fiber tracts in vivo, diffusion tensor tractog... more Despite its potential for visualizing white matter fiber tracts in vivo, diffusion tensor tractography has found only limited applications in clinical research in which specific anatomic connections between distant regions need to be evaluated. We introduce a robust method for fiber clustering that guides the separation of anatomically distinct fiber tracts and enables further estimation of anatomic connectivity between distant brain regions. Line scanning diffusion tensor images (LSDTI) were acquired on a 1.5T magnet. Regions of interest for several anatomically distinct fiber tracts were manually drawn; then, white matter tractography was performed by using the Runge-Kutta method to interpolate paths (fiber traces) following the major directions of diffusion, in which traces were seeded only within the defined regions of interest. Next, a fully automatic procedure was applied to fiber traces, grouping them according to a pairwise similarity function that takes into account the sha...
The perception of a visual stimulus can be inhibited by occipital transcranial magnetic stimulati... more The perception of a visual stimulus can be inhibited by occipital transcranial magnetic stimulation. This visual suppression effect has been attributed to disruption in the cortical gray matter of primary visual cortex or in the fiber tracts leading to V1 from the thalamus. However, others have suggested that the visual suppression effect is caused by disruption in secondary visual cortex. Here the authors used a figure-eight coil, which produces a focal magnetic field, and a Quadropulse stimulator to produce visual suppression contralateral to the stimulated hemisphere in five normal volunteer subjects. The authors coregistered the stimulation sites with magnetic resonance images in these same subjects using optical digitization. The stimulation sites were mapped onto the surface of the occipital lobes in three-dimensional reconstructions of the cortical surface to show the distribution of the visual suppression effect. The results were consistent with disruption of secondary visual cortical areas.
Postmortem, magnetic resonance, and event-related potential studies suggest the presence of tempo... more 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.
ABSTRACT Background / Purpose: The cingulum bundle is the major white matter tract connecting the... more ABSTRACT Background / Purpose: The cingulum bundle is the major white matter tract connecting the cortex and limbic system, and is involved in memory, reasoning and emotion. It has been observed to be abnormal in patients with chronic schizophrenia (Kubicki et al 2007), but it has been less studied in first episode (FE).18 patients with FE schizophrenia, 20 patients with chronic schizophrenia (CSZ) and 20 controls were matched to each patient group (FENC and CSZNC), and received diffusion imaging on a 3T GE MRI. Two regions of interest, anterior and posterior portions of the cingulum bundle, were manually placed for each subject to initiate streamlined tractography. After successful fiber tracking, mean trace (TR), fractional anisotropy (FA), axial and radial diffusivity (AD and RD) were calculated for each subject. Main conclusion: FE exhibited higher TR in comparison to FENC in both hemispheres and on the left in comparison to CSZ. AD was increased in the FE bilaterally in comparison to FENC and CSZ. RD was higher in FE compared to FENC bilaterally and was correlated with delusions of reference.These results suggest that both axial and radial diffusivity contribute to the change in overall white matter health and organization between first episode and chronic schizophrenia, reflecting abnormalities in both axon integrity and myelination. In particular anomalies in myelin integrity may be related to the severity of delusions of reference. This is consistent with abnormal myelin development that results in partial degeneration of the underlying axons.
Seeking to unite psychological and biological approaches, this paper links cognitive and cellular... more Seeking to unite psychological and biological approaches, this paper links cognitive and cellular hypotheses and data about thought and language abnormalities in schizophrenia. The common thread, it is proposed, is a dysregulated suppression of associations (at the behavioral and functional neural systems level), paralleled by abnormalities of inhibition at the cellular and molecular level, and by an abnormal anatomical substrate (reduced MRI gray matter volume) in areas subserving language. At the level of behavioral experiments and connectionist modeling, data suggest an abnormal semantic network connectivity (strength of associations) in schizophrenia, but not an abnormality of network size (number of associates). This connectivity abnormality is likely to be a preferential processing of the dominant (strongest) association, with the neglect of preceding contextual information. At the level of functional neural systems, the N400 event-related potential amplitude is used to index ...
Despite its potential for visualizing white matter fiber tracts in vivo, diffusion tensor tractog... more Despite its potential for visualizing white matter fiber tracts in vivo, diffusion tensor tractography has found only limited applications in clinical research in which specific anatomic connections between distant regions need to be evaluated. We introduce a robust method for fiber clustering that guides the separation of anatomically distinct fiber tracts and enables further estimation of anatomic connectivity between distant brain regions. Line scanning diffusion tensor images (LSDTI) were acquired on a 1.5T magnet. Regions of interest for several anatomically distinct fiber tracts were manually drawn; then, white matter tractography was performed by using the Runge-Kutta method to interpolate paths (fiber traces) following the major directions of diffusion, in which traces were seeded only within the defined regions of interest. Next, a fully automatic procedure was applied to fiber traces, grouping them according to a pairwise similarity function that takes into account the sha...
The perception of a visual stimulus can be inhibited by occipital transcranial magnetic stimulati... more The perception of a visual stimulus can be inhibited by occipital transcranial magnetic stimulation. This visual suppression effect has been attributed to disruption in the cortical gray matter of primary visual cortex or in the fiber tracts leading to V1 from the thalamus. However, others have suggested that the visual suppression effect is caused by disruption in secondary visual cortex. Here the authors used a figure-eight coil, which produces a focal magnetic field, and a Quadropulse stimulator to produce visual suppression contralateral to the stimulated hemisphere in five normal volunteer subjects. The authors coregistered the stimulation sites with magnetic resonance images in these same subjects using optical digitization. The stimulation sites were mapped onto the surface of the occipital lobes in three-dimensional reconstructions of the cortical surface to show the distribution of the visual suppression effect. The results were consistent with disruption of secondary visual cortical areas.
Postmortem, magnetic resonance, and event-related potential studies suggest the presence of tempo... more 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.
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Papers by M. Shenton