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.
"Intriguingly, a dysfunction of this area has been linked to schizophrenia in a structural, neurophysiological and functional way. Parietal volume reductions are common morphological characteristics in schizophrenia spectrum disorders (Zhou et al. 2007), and interestingly, a relation between first rank symptoms and an existing significant deficit in right inferior parietal lobule cortical thickness was found (Venkatasubramanian et al. 2011). This supports the notion that a deficit in the posterior parietal region is critical for the manifestation of overt psychotic symptoms. "
[Show abstract][Hide abstract] ABSTRACT: The phenomenon known as "perceptual pseudoneglect" refers to the leftward bias in visuospatial attention in non-clinical samples, possibly as a consequence of right hemisphere dominance for visuospatial attention. The degree of such a lateralized visuospatial attention bias is often assessed using the line bisection task. Interestingly, various psychiatric disorders may influence the expression of this phenomenon. The aim of this paper was to perform a critical appraisal of the literature on the expression of the perceptual pseudoneglect across all psychiatric disorders accompanied by meta-analytical evaluation of the data. Moreover, we will discuss whether this phenomenon may be considered as a trait marker across different psychiatric disorders.
"To the best of our knowledge, only a few structural MRI studies have investigated PoCG in SCZ patients using a region of interest (ROI) method, with the results being inconclusive (Niznikiewicz et al., 2000; Nierenberg et al., 2005; Zhou et al., 2007). Zhou et al. (2007) reported a reduction of PoCG gray and white matter in patients with SCZ compared to healthy subjects. Alterations in white matter connectivity may reflect abnormalities at the level of the gray matter (Brambilla and Tansella, 2007). "
[Show abstract][Hide abstract] ABSTRACT: The post-central gyrus (PoCG) has received little attention in brain imaging literature. However, some magnetic resonance imaging (MRI) studies have detected the presence of PoCG abnormalities in patients with schizophrenia. Fifty-six first-episode schizophrenia patients, selected through the PAFIP Program and carefully assessed for dimensional psychopathology and cognitive functioning, and 56 matched healthy controls were scanned twice over 1-year follow-up. PoCG gray matter volumes were measured at both time-points and compared between the groups. Differences in volume change over time and the relationship between PoCG volume and clinical and cognitive variables were also investigated. The right PoCG volume was significantly smaller in patients than in controls at the 1-year follow-up; furthermore, it was significantly smaller in male patients compared with male controls, with no differences in female. Although there was no significant time by group interaction in the overall sample, a trend-level interaction was found for the right PoCG in males. This is the first study, as per our knowledge, to focus on PoCG in first-episode schizophrenia patients. The presence of PoCG abnormalities in the first year of schizophrenia suggests a possible contribution to the pathophysiology of the illness, probably as part of a more extensive network of abnormalities.
"This result has been hypothesized as being linked to a reduced or reversed brain asymmetry with a deficit of right hemisphere functions (Michel et al., 2007; Zivotofsky et al., 2007; McCourt et al., 2008; Rao et al., 2010; Ribolsi et al., 2013) and in particular of the right parietal cortex in SCZ (Petty, 1999; Malhotra et al., 2009; Venkatasubramanian et al., 2011). Intriguingly a dysfunction of this area has been linked to schizophrenia in a structural, neurophysiological and functional way (Zhou et al., 2007; Kato et al., 2011; Venkatasubramanian et al., 2011). Interestingly, in a recent study conducted by our research group, selective transcranial direct current stimulation (tDCS) of right posterior parietal cortex was able to determine a partial correction of the lack of leftward bias in a group of medicated SCZ, confirming the hypothesis of the involvement of this area in the onset of this phenomenon (Ribolsi et al., 2013). "
[Show abstract][Hide abstract] 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).
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.
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 11/2013; 4:846. DOI:10.3389/fpsyg.2013.00846 · 2.80 Impact Factor
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