Abstract
The right hemispheric dominance in visuospatial attention in human brain has been well established. Converging evidence has documented that ventral posterior parietal cortex (PPC) plays an important role in visuospatial attention. The role of dorsal PPC subregions, especially the superior parietal lobule (SPL) in visuospatial attention is still controversial. In the current study, we used repetitive transcranial magnetic stimulation (rTMS) and diffusion magnetic resonance imaging (MRI) techniques to test the role of posterior SPL in visuospatial attention and to investigate the potential neuroanatomical basis for right hemisphere dominance in visuospatial function. Transcranial magnetic stimulation (TMS) results unraveled that the right SPL predominantly mediated visuospatial attention compared to left SPL. Anatomical connections analyses between the posterior SPL and the intrahemispheric frontal subregions and the contralateral PPC revealed that right posterior SPL has stronger anatomical connections with the ipsilateral middle frontal gyrus (MFG), with the ipsilateral inferior frontal gyrus (IFG), and with contralateral PPC than that of the left posterior SPL. Furthermore, these asymmetric anatomical connections were closely related to behavioral performances. Our findings indicate that SPL plays a crucial role in regulating visuospatial attention, and dominance of visuospatial attention results from unbalanced interactions between the bilateral fronto-parietal networks and the interhemispheric parietal network.
Highlights
Cerebral asymmetry, which has been characterized by both its functions and its connections, is a fundamental property of the human brain and a marker of successful development (Liu et al, 2009; Bishop, 2013)
Mapping the Anatomical Connections between the superior parietal lobule (SPL) and the Ipsilateral Frontal Subregions To detect whether unbalanced interhemispheric interaction between the bilateral fronto-parietal networks results in asymmetric visuospatial ability, we studied whether asymmetry of visuospatial attention was related to asymmetric anatomical connections between the bilateral posterior SPLs with their ipsilateral frontal subregions
Anatomical connectivity mapping analyses revealed that the asymmetry of visuospatial attention was mediated by both the fronto-parietal network and the contralateral posterior parietal cortex (PPC) network via the superior longitudinal fasciculus (SLF) II, extreme capsule (EmC) and posterior corpus callosum (CC)
Summary
Cerebral asymmetry, which has been characterized by both its functions and its connections, is a fundamental property of the human brain and a marker of successful development (Liu et al, 2009; Bishop, 2013). Neuropsychological and transcranial magnetic stimulation (TMS) studies have revealed that visuospatial attention was primarily controlled by the right ventral posterior parietal cortex (PPC; Arrington et al, 2000; Corbetta et al, 2000; Driver and Vuilleumier, 2001; Hilgetag et al, 2001; Vallar, 2001; Bjoertomt et al, 2002; Mort et al, 2003; Kincade et al, 2005), whereas the role of the dorsal PPC subregions, especially the superior parietal lobule (SPL) in visuospatial attention has not been well studied. A recent study using intraoperative electrical stimulation which is considered to be the gold standard to determine the brain function in awake patients during brain tumor surgery showed that stimulation of the right posterior SPL resulted in visuospatial neglect (Vallar et al, 2014). The discrepancy between the neuropsychological findings and the findings obtained from brain damaged patients raises the question what’s the role of posterior SPL in visuospatial attention
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