Vaessen Maarten J, Saj Arnaud, Lovblad Karl-Olof, Gschwind Markus, Vuilleumier Patrik
Laboratory for Neurology and Imaging of Cognition, Department of Neurosciences, University Medical Centre, Geneva, Switzerland; Department of Clinical Neurology, University Hospital of Geneva, Geneva, Switzerland.
Laboratory for Neurology and Imaging of Cognition, Department of Neurosciences, University Medical Centre, Geneva, Switzerland; Department of Clinical Neurology, University Hospital of Geneva, Geneva, Switzerland.
Cortex. 2016 Apr;77:54-68. doi: 10.1016/j.cortex.2015.12.008. Epub 2016 Jan 19.
Spatial neglect is a neuropsychological syndrome in which patients fail to perceive and orient to stimuli located in the space contralateral to the lesioned hemisphere. It is characterized by a wide heterogeneity in clinical symptoms which can be grouped into distinct behavioral components correlating with different lesion sites. Moreover, damage to white-matter (WM) fiber tracts has been suggested to disconnect brain networks that mediate different functions associated with spatial cognition and attention. However, it remains unclear what WM pathways are associated with functionally dissociable neglect components. In this study we examined nine patients with a focal right hemisphere stroke using a series of neuropsychological tests and diffusion tensor imaging (DTI) in order to disentangle the role of specific WM pathways in neglect symptoms. First, following previous work, the behavioral test scores of patients were factorized into three independent components reflecting perceptual, exploratory, and object-centered deficits in spatial awareness. We then examined the structural neural substrates of these components by correlating indices of WM integrity (fractional anisotropy) with the severity of deficits along each profile. Several locations in the right parietal and frontal WM correlated with neuropsychological scores. Fiber tracts projecting from these locations indicated that posterior parts of the superior longitudinal fasciculus (SLF), as well as nearby callosal fibers connecting ipsilateral and contralateral parietal areas, were associated with perceptual spatial deficits, whereas more anterior parts of SLF and inferior fronto-occipital fasciculus (IFOF) were predominantly associated with object-centered deficits. In addition, connections between frontal areas and superior colliculus were found to be associated with the exploratory deficits. Our results provide novel support to the view that neglect may result from disconnection lesions in distributed brain networks, but also extend these notions by highlighting the role of dissociable circuits in different functional components of the neglect syndrome. However these preliminary findings require replication with larger samples of patients.
空间忽视是一种神经心理学综合征，患者无法感知和定向位于受损半球对侧空间的刺激。其临床症状具有广泛的异质性，可分为与不同病变部位相关的不同行为成分。此外，有人认为白质（WM）纤维束的损伤会切断介导与空间认知和注意力相关的不同功能的脑网络。然而，尚不清楚哪些WM通路与功能可分离的忽视成分相关。在本研究中，我们对9名右侧半球局灶性中风患者进行了一系列神经心理学测试和弥散张量成像（DTI），以厘清特定WM通路在忽视症状中的作用。首先，根据之前的研究，将患者的行为测试分数分解为三个独立成分，反映空间意识中的感知、探索和以物体为中心的缺陷。然后，我们通过将WM完整性指标（分数各向异性）与每个特征曲线的缺陷严重程度进行关联，来研究这些成分的结构神经基础。右侧顶叶和额叶WM的几个位置与神经心理学分数相关。从这些位置投射出的纤维束表明，上纵束（SLF）的后部以及连接同侧和对侧顶叶区域的胼胝体纤维与感知空间缺陷相关，而SLF的更前部和额枕下束（IFOF）主要与以物体为中心的缺陷相关。此外，发现额叶区域与上丘之间的连接与探索性缺陷相关。我们的结果为忽视可能源于分布式脑网络中的连接中断性病变这一观点提供了新的支持，但也通过强调可分离回路在忽视综合征不同功能成分中的作用扩展了这些概念。然而，这些初步发现需要在更大的患者样本中进行重复验证。
