Hemispheric asymmetry and callosal integration of visuospatial attention in schizophrenia: A tachistoscopic line bisection study

Abstract

Background-A hallmark of visuospatial neglect syndrome is that patients with lesions to right parietal cortex misbisect horizontal lines far rightward of veridical center. Neurologically normal subjects misbisect lines with a systematic leftward bias (pseudoneglect). Both phenomena, as well as neuroimaging studies, disclose a predominant right hemisphere control of spatial attention. Numerous studies of patients with schizophrenia have implicated global deficits of either right or left hemisphere function, as well as compromised integrity of the corpus callosum.Methods-To better understand the functional implications of schizophrenia we utilized a forcedchoice tachistoscopic line bisection task to probe the status of right hemisphere control of spatial attention, and compared left-versus right-hand unimanual responses to index the degree of callosal transfer of visuospatial information in both patient and control groups.Results-In contrast to the significant leftward bisection errors of control subjects, patients exhibit no significant leftward error. Whereas control subjects evince a significant correlation between leftand right-hand bisection errors, patients lack a significant intermanual correlation.Conclusions-The lack of significant leftward bisection error of patients implies a deficit of right hemisphere function. The lack of a significant correlation between left-and right-hand bisection errors in patients implies a loss of callosal integrity.

Right fronto-parietal dysfunction underlying spatial attention in bipolar disorder

“…The present study confirms previous studies that have used the visual line bisection task as a valuable tool for assessing the functional brain organization associated with the pathophysiology of different neuropsychiatric disorders (Barnett, 2006;McCourt et al, 2008). For example, line bisection studies in children with attention-deficit hyperactivity disorder have consistently shown a rightward bias in spatial attention, suggesting a right hemisphere inefficiency associated with symptoms of severe impulsivity and/or hyperactivity (Sheppard et al, 1999;Manly et al, 2005;Rolfe et al, 2008;Waldie and Hausmann, 2010).…”

“…Also, the leftward bias in line bisection (i.e., pseudoneglect) that usually characterizes the right-hemisphere dominance for the allocation of visuospatial attention observed in neurologically normal subjects was increased in dependent personality disorder (Wang et al, 2003), and similar to the present study, significantly reduced in schizophrenia (Mather et al, 1990;Barnett, 2006;Zivotofsky et al, 2007;McCourt et al, 2008). Thus, these findings suggest that the visual line bisection is sensitive to atypical functional brain organization across different neuropsychiatric disorders.…”

Visual sensory processing deficits in Schizophrenia and their relationship to disease state

“…An association between the reduced P1 amplitude and impairment in the magnocellular (M) pathway has also been drawn [7,9,23] and evidence from behavioural studies has also pointed to impairments in this system [33,45,57). The M pathway is the part of the visual system responsible for the rapid conduction of low-resolution visual information to the cortex and is involved in processing of overall stimulus organization [46,62,66].…”

Lateralization of Brain Functions: A Randomized Single-Blinded Observational Study

“…However, there has been numerous several other studies and attempts, for correlating the effect of cerebral lateralization and visual analytic skills, using other investigative tools, including: tachistoscopic recognition; facial recognition; visuospatial attention; written verbal commands; Japanese kanji; and reaction-time studies; and functional MRI (fMRI) (19)(20)(21)(22)(23)(24)(25). Other parallel studies also examined subject with some neurological pathologies, including dyslexia; developmental disorders; and autism (26)(27)(28).…”