Parietal lobe volume deficits in schizophrenia spectrum disorders.
ABSTRACT There has been little attention given to whether parietal lobe structural deficits are present in patients with schizophrenia and related personality disorders. The current study was designed to examine parietal volume alterations between schizophrenia and schizotypal personality disorder. Twenty-five patients with schizotypal disorder, 53 patients with schizophrenia, and 59 healthy volunteers were scanned using high-resolution magnetic resonance imaging (MRI). Volume measurements of the postcentral gyrus (PoCG), precuneus, superior parietal gyrus (SuPG), supramarginal gyrus (SMG), and angular gyrus (AGG) were performed on consecutive 1-mm coronal slices. Gray matter volumes were reduced in all parietal subregions in patients with schizophrenia compared with healthy controls. White matter volumes were also reduced in the SuPG and PoCG. In contrast, the schizotypal subjects had gray matter reductions only in the PoCG, while other regions were not affected. In addition, there was a lack of normal significant-leftward asymmetry in the SMG in schizophrenia. These findings demonstrate that volume reductions in the somatosensory cortices are common morphological characteristics in schizophrenia spectrum disorders. The additional volume alterations in schizophrenia may support the notion that a deficit in the posterior parietal region is critical for the manifestation of overt psychotic symptoms.
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ABSTRACT: Saccades to peripheral targets require a direct visuomotor transformation. In contrast, antisaccades, saccades in opposite direction of a peripheral target, require more complex transformation processes due to the inversion of the spatial vector. Here, the differential neural mechanisms underlying sensorimotor control in saccades and antisaccades were investigated using functional magnetic resonance imaging (fMRI) at 3T field strength in 22 human volunteers. We combined a task factor (prosaccades: look towards target; antisaccades: look away from target) with a parametric factor of transformation demand (single vs. multiple peripheral targets) in a two-factorial block design. Behaviourally, a greater number of peripheral targets resulted in decreased spatial accuracy and increased reaction times in antisaccades. No effects were seen on the percentage of antisaccade direction errors or on any prosaccade measures. Neurally, a greater number of targets led to increased BOLD signal in the posterior parietal cortex (PPC) bilaterally. This effect was partially qualified by an interaction that extended into somatosensory cortex, indicating greater increases during antisaccades than prosaccades. The results implicate the PPC as a sensorimotor interface that is especially important in nonstandard mapping for antisaccades and point to a supportive role of somatosensory areas in antisaccade sensorimotor control, possibly by means of proprioceptive processes.NeuroImage 08/2014; · 6.13 Impact Factor
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ABSTRACT: Background and Objectives: Alterations and deficits of oligodendrocytes reported in the grey and white matter in schizophrenia may contribute to neuronal disconnectivity. Prefrontal-parietal functional disconnections have been implicated in diverse clinical symptoms of schizophrenia, including poor insight. We studied the effects of schizophrenia diagnosis and insight on numerical density (Nv) of oligodendrocytes in the inferior parietal lobule (IPL). Methods: Nissl-stained sections from the Stanley "Parietal Collection" from male schizophrenia subjects (n = 24) having poor, fair, or good insight and healthy matched controls (n = 24) were examined. The Nv of oligodendrocytes was estimated in layer 3 of BA 39 and BA 40 of the IPL and in white matter underlying layer 6 by optical dissector method. Results: In BA 39 we found a significant 15% decrease in the Nv of oligodendrocytes in layer 3 in the schizophrenia group. Nv of oligodendrocytes in the poor+fair insight subgroup was 20% lower compared to controls (p< 0.05) and to good insight subgroup (p = 0.055). Nv of oligodendrocytes in the good insight subgroup did not differ from the control group. A significant lateralization of oligodendrocyte density was detected in layer 3 (L>R) only in the control group. There were no significant group differences in the Nv of oligodendrocytes in BA 40 or in the white matter underlying BA 39/40 areas. Conclusions: Lack of insight in schizophrenia may be associated with a deficit of oligodendroglia in the grey matter of IPL.European Journal of Psychiatry 06/2013; 27(2):111-121. · 0.46 Impact Factor
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ABSTRACT: Introduction: Recent studies have found a lack of normal pseudoneglect in schizophrenia patients and in their first degree relatives. Similarly, several contributions have reported that measures of schizotypy in the healthy population may be related to signs of right-sided lateralization, but most of these studies differ greatly in methodology (sample size, choice of schizotypy scales, and laterality tasks) and, consequently, the results cannot be compared and so definitive conclusion cannot be drawn. In this study, our purpose is to investigate whether some tasks of spatial attention may be related to different dimensions of schizotypy not only in a larger sample of healthy subjects (HS), but testing the same people with several supposedly related measures several times. Materials and Methods: In the first part of the study (Part I), the performance on "paper and pencil" line bisection (LB) tasks in 205 HS was investigated. Each task was repeated three times. In the second part of the study (Part II), a subgroup of 80 subjects performed a computerized version of the LB test and of the mental number line bisection (MNL) test. In both parts of the study, every subject completed the 74-item version of the Schizotypal Personality Questionnaire (SPQ) and the Edinburgh Handedness Inventory (EHI). Results: In both parts of the study, high scores on the subscale "magical thinking" of SPQ have resulted in being closely linked to a decreased pseudoneglect as assessed by the LB task. On the contrary, right handedness is related to an increased leftward bias at the same task. No association was found between MNL and the other variables. Discussion: The main finding of this study is that a decreased spatial leftward bias at the LB task correlates with positive schizotypy in the healthy population. This finding supports the hypothesis that a deviation from leftward hemispatial visual preference may be related to the degree of psychosis-like schizotypal signs in non-clinical population and should be investigated as a possible marker of psychosis.Frontiers in Psychology 01/2013; 4:846. · 2.80 Impact Factor