Kaufmann Brigitte Charlotte, Knobel Samuel Elia Johannes, Nef Tobias, Müri René Martin, Cazzoli Dario, Nyffeler Thomas
Perception and Eye Movement Laboratory, Departments of Neurology and BioMedical Research, Inselspital, Bern University Hospital, University of Bern, Bern, Switzerland.
Neurocenter, Luzerner Kantonsspital, Lucerne, Switzerland.
Front Neurosci. 2020 Jan 22;13:1412. doi: 10.3389/fnins.2019.01412. eCollection 2019.
Video-oculography during free visual exploration (FVE) is a valuable tool to evaluate visual attention spatial allocation in neglect patients after right-hemispheric stroke. In conventional FVE analyses, the position of a visual fixation is conceived as a single point in space. Here, we describe a new complementary method to analyze FVE data based on foveal vision, leading to an accurate estimate of the portion of the picture that was effectively explored. In 15 neglect patients and 20 healthy controls, visual exploration areas (i.e., considering 1° visual angle around every single fixation) were computed. Furthermore, the proportion of single and overlapping fixations was analyzed. Overlapping fixations were further categorized into capture fixations (successive overlapping fixation, putatively reflecting problem of disengagement) and re-capture fixations (temporally distant overlapping fixations, putatively reflecting spatial working memory deficits). The results of this new analysis approach were compared to the ones of conventional approaches. Conventional analyses showed the typical visual attention deficits in neglect patients versus healthy controls: significantly less fixations and time spent within the left and significantly more fixations and time spent within the right screen half. According to the results of our new approach, patients showed a significantly smaller visual exploration area within the left screen half. However, the right visual exploration area did not differ between groups. Furthermore, in neglect patients, the proportion of overlapping fixations within the right screen half was significantly higher than within the left screen half, as well as significantly higher than in healthy controls within either screen halves. Whereas neglect patients showed significantly more capture fixations than healthy controls, the number of re-capture fixations did not differ between groups. These results suggest that, in neglect patients, the efficiency of visual exploration is also reduced within the right screen half and that impaired disengagement might be an important mechanism leading to overlapping fixations. Our new analysis of the visual exploration area, based on foveal vision, may be a promising additional approach in visual attention research. It allows to accurately measure the portion of the picture that was effectively explored, disentangle single from overlapping fixations, and distinguish between capture and re-capture fixations.
在自由视觉探索（FVE）过程中进行视频眼动描记术，是评估右半球卒中后忽视患者视觉注意力空间分配的一项重要工具。在传统的FVE分析中，视觉注视点的位置被视为空间中的一个单点。在此，我们描述了一种基于中央凹视觉分析FVE数据的新的补充方法，从而能够准确估计有效探索的图片部分。对15名忽视患者和20名健康对照者计算了视觉探索区域（即考虑每个注视点周围1°视角）。此外，还分析了单个注视点和重叠注视点的比例。重叠注视点进一步分为捕获注视点（连续重叠注视点，推测反映脱离困难问题）和重新捕获注视点（时间上相隔较远的重叠注视点，推测反映空间工作记忆缺陷）。将这种新分析方法的结果与传统方法的结果进行了比较。传统分析显示，与健康对照者相比，忽视患者存在典型的视觉注意力缺陷：左半侧屏幕内的注视点和停留时间明显减少，右半侧屏幕内的注视点和停留时间明显增多。根据我们新方法的结果，患者左半侧屏幕内的视觉探索区域明显更小。然而，右半侧视觉探索区域在两组之间并无差异。此外，在忽视患者中，右半侧屏幕内重叠注视点的比例明显高于左半侧屏幕内，也明显高于健康对照者在任一屏幕半侧内的比例。忽视患者的捕获注视点明显多于健康对照者，而重新捕获注视点的数量在两组之间并无差异。这些结果表明，在忽视患者中，右半侧屏幕内的视觉探索效率也有所降低，且脱离困难可能是导致重叠注视点的一个重要机制。我们基于中央凹视觉对视觉探索区域进行的新分析，可能是视觉注意力研究中一种很有前景的补充方法。它能够准确测量有效探索的图片部分，区分单个注视点和重叠注视点，并区分捕获注视点和重新捕获注视点。
