Saj Arnaud, Pierce Jordan, Caroli Alice, Ronchi Roberta, Thomasson Marine, Vuilleumier Patrik
Neurology Department, University Hospital of Geneva, Geneva, Switzerland; Neuroscience Department, Laboratory for Behavioral Neurology and Imaging of Cognition, University of Geneva, Switzerland; CRIR/Institut Nazareth et Louis-Braille du CISSS de la Montérégie-Centre, Longueuil, QC, Canada; Department of Psychology, University of Montréal, Québec, Canada.
Neuroscience Department, Laboratory for Behavioral Neurology and Imaging of Cognition, University of Geneva, Switzerland.
Cortex. 2020 Jan;122:187-197. doi: 10.1016/j.cortex.2019.10.002. Epub 2019 Oct 30.
Spatial remapping implies the updating and maintaining of the spatial position of objects in successive visual images across time, despite their displacement on the retina due to eye movements. In the parietal cortex, the representation of spatial locations appears to be partly centered on gaze direction, and thus modulated by current eye-gaze position. It has been suggested that short-term memory for spatial locations across delays might be impaired in right brain-injured patients with left spatial neglect, but more so after rightward than leftward gaze shifts - an asymmetry attributed to a loss of spatial representations normally transferred from left to right hemisphere during remapping. Because several studies point to a strong link between attentional and oculomotor circuits in the brain, we hypothesized that similar remapping effects might result from attentional displacements without overt eye movements. We tested this hypothesis in right-brain damaged patients with and without left neglect in a visuo-spatial memory task. As predicted, neglect patients showed a selective deficit in location memory following an exogenous attentional shift caused by a brief flash in the periphery of their right (but not left) visual field. We conclude that an attentional displacement without eye movements is sufficient to remap spatial representations across hemifields, and that this process is impaired in neglect patients when a location has to be transferred to the neglected/left side relative to current gaze or attention focus. More generally, these results support the notion of neural overlap between oculomotor and attentional mechanisms, and confirm a role for impaired remapping in the neglect syndrome, wherein spatial representations of contralesional locations may fail to be maintained during active attentional behavior.
空间重映射意味着，尽管物体因眼球运动而在视网膜上发生位移，但在连续的视觉图像中，其空间位置会随时间更新并得以维持。在顶叶皮层中，空间位置的表征似乎部分以注视方向为中心，因此会受到当前眼注视位置的调节。有人提出，患有左侧空间忽视的右脑损伤患者，在延迟期间对空间位置的短期记忆可能会受损，但向右注视转移后比向左注视转移后受损更严重——这种不对称性归因于在重映射过程中通常从左半球转移到右半球的空间表征丧失。由于多项研究指出大脑中注意力和眼动回路之间存在紧密联系，我们推测，在没有明显眼球运动的情况下，注意力的转移可能会产生类似的重映射效应。我们在一项视觉空间记忆任务中，对患有和未患有左侧忽视的右脑损伤患者进行了这一假设的测试。正如预期的那样，忽视患者在右侧（而非左侧）视野边缘的短暂闪光引起的外源性注意力转移后，在位置记忆方面表现出选择性缺陷。我们得出结论，没有眼球运动的注意力转移足以在半视野间重映射空间表征，并且当一个位置必须相对于当前注视或注意力焦点转移到被忽视的/左侧时，这个过程在忽视患者中会受损。更普遍地说，这些结果支持了眼动和注意力机制之间神经重叠的观点，并证实了重映射受损在忽视综合征中的作用，即在主动注意力行为期间，对侧病灶位置的空间表征可能无法维持。
