Abstract
Functional magnetic resonance imaging (fMRI) is a neuroimaging tool which has been applied extensively to explore the pathophysiological mechanisms of neurological disorders. Spatial neglect is considered to be the failure to attend or respond to stimuli on the side of the space or body opposite a cerebral lesion. In this review, we summarize and analyze fMRI studies focused specifically on spatial neglect. Evidence from fMRI studies have highlighted the role of dorsal and ventral attention networks in the pathophysiological mechanisms of spatial neglect, and also support the concept of interhemispheric rivalry as an explanatory model. fMRI studies have shown that several rehabilitation methods can induce activity changes in brain regions implicated in the control of spatial attention. Future investigations with large study cohorts and appropriate subgroup analyses should be conducted to confirm the possibility that fMRI might offer an objective standard for predicting spatial neglect and tracking the response of brain activity to clinical treatment, as well as provide biomarkers to guide rehabilitation for patients with SN.
Highlights
spatial neglect (SN) can occur subsequent to neurodegenerative disease [3, 4], cancer [5], trauma [6], but it occurs most commonly subsequent to stroke [7, 8]
FMRI opens the way for greater understanding of the pathophysiological mechanisms underlying SN and potentially improves our ability to evaluate the effect of rehabilitation methods. Functional magnetic resonance imaging (fMRI) studies have demonstrated that SN might result from abnormal changes in attention networks and other brain functional networks, including the default mode network (DMN) and motor network
Several promising interventions (PA, non-invasive brain stimulation (NIBS), motor imagery (MI), optokinetic stimulation (OKS), and virtual reality (VR)) could modulate the cortical regions implicated in spatial cognition measured by fMRI, which might contribute to a beneficial effect to the clinical presentation of SN
Summary
“Spatial neglect” (SN) is a contralesional spatial bias (i.e., the failure to attend or respond to stimuli on the side of the space or body opposite the lesion) [1]. Lesions in parts of the VAN have been shown to evoke profound activation changes in parts of the structurally intact DAN measured by resting-state functional connectivity MRI which, in turn, correlates with SN severity in stroke patients [39, 49]. The fractional amplitude of lowfrequency fluctuations of the BOLD signal in resting-state fMRI in the structurally intact right SPL (as part of the DAN) is strongly correlated with the SN-related functional impairment and pathological attention bias in SN patients with structural damage to the VAN [39]. Wang and colleagues, using repetitive TMS and resting-state functional connectivity fMRI, indicated that a TMS-induced unbalanced interaction between the interhemispheric top–down network of posterior SPL and V1 correlated with lateralization of visuospatial attention in healthy individuals [57]. The interhemispheric-rivalry model has been supported by evidence showing that behavioral deficits of SN patients were improved when TMS over the left PPC or left frontal cortex was employed to normalize the overexcitability of the contralesional hemisphere for interhemispheric rebalance [58, 59]
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