Schizophrenia and the Neglect Syndrome: Parietal Contributions to Cognitive Dysfunction in Schizophrenia

Abstract

Many of the positive symptoms of schizophrenia, including hallucinations and passivity phenomena, have been related to dysfunction within association cortices. In addition, many of the cognitive deficits observed in patients with schizophrenia can also be characterised as impairments of higher level cognitions known to depend on these same association cortices. While most attention has been directed towards dysfunction of the frontal and temporal cortices, there is mounting evidence for impaired functioning of the parietal cortices as well. That is, there is a substantial body of research demonstrating impaired spatial and motor behaviours in patients with schizophrenia -behaviours known to depend on the parietal cortex. In this selective review we contrast some of these impairments with a neurological syndrome that commonly arises from damage to the right parietal cortex, known as unilateral neglect. Although the spatial impairments characteristic of neglect are far more severe than those observed in patients with schizophrenia, there are some important parallels that make the comparison worthwhile. We intend to outline those parallels and highlight ways in which they may inform models of schizophrenia.

Anti-Extinction in Patients With Schizophrenia

“…It should be mentioned that both findings of this study, right hemi-neglect and anti-extinction effect, support other studies that have suggested parietal lobe dysfunction in patients with schizophrenia (21,30,31). Indeed, right hemi-spatial neglect might indicate either impairment of the left parietal lobe in allocation of attention to the right visual space, or hyperactivity of right parietal lobe leading to more saliency of the left visual field (21). In support of this, Posner et al (1988) found that patients demonstrated attentional deficits to the targets in the right visual field similar to patients, who had a left hemisphere lesion (32).…”

“…Moreover, in the task design, the distance between the 2 targets was small (less than 15°), thus grouping effect in this distance might have better helped patients detect bilateral stimuli (29). It should be mentioned that both findings of this study, right hemi-neglect and anti-extinction effect, support other studies that have suggested parietal lobe dysfunction in patients with schizophrenia (21,30,31). Indeed, right hemi-spatial neglect might indicate either impairment of the left parietal lobe in allocation of attention to the right visual space, or hyperactivity of right parietal lobe leading to more saliency of the left visual field (21).…”

“…Particularly, researchers have reported evidence of visual and representational hemispatial neglect in these patients, as evidence for parietal lobe dysfunction (21)(22)(23)(24). However, to date no study has examined extinction and anti-extinction in patients with schizophrenia.…”

Asymmetries of Visuospatial Attention in Schizophrenia

“…This hypothesis was supported by previous literature implicating right parietal abnormalities in schizophrenia [57][58][59][60][61]. Zhou et al [62], using highresolution magnetic resonance imaging (MRI), evaluated volume features of parietal subregions (postcentral gyrus, precuneus, superior parietal gyrus, supramarginal gyrus, and angular gyrus) and found that gray matter volumes were reduced in these regions in PS as compared with healthy controls.…”

Exceptional visuospatial imagery in schizophrenia; implications for madness and creativity

“…Based on previous literature implicating parietal abnormalities in SZ in general (Torrey, 2007 for a review) and spatial neglect in particular (Cavezian et al, 2006), we predicted that SZ would demonstrate greater magnitude of LB biases compared with HC (i.e., more right biases). Furthermore, since previous neuroimaging research has demonstrated a relationship between passivity delusions and right parietal abnormalities (Maruff et al, 2005), we predicted that right LB deviations would be related to delusional ideation as quantified by the Peters' et al Delusions Inventory (PDI).…”