PDF(Pubmed)
Abstract：
The existence of unconscious visually triggered behavior in patients with cortical blindness (e.g., homonymous hemianopia) has been amply demonstrated and the neural bases of this phenomenon have been thoroughly studied. However, a crosstalk between the two hemispheres as a possible mechanism of unconscious or partially conscious vision has not been so far considered. Thus, the aim of this study was to assess the relationship between structural and functional properties of the corpus callosum (CC), as shown by probabilistic tractography (PT), behavioral detection/discrimination performance and level of perceptual awareness in the blind field of patients with hemianopia. Twelve patients were tested in two tasks with black-and-white visual square-wave gratings, one task of movement and the other of orientation. The stimuli were lateralized to one hemifield either intact or blind. A PT analysis was carried out on MRI data to extract fiber properties along the CC (genu, body, and splenium). Compared with a control group of participants without brain damage, patients showed lower FA values in all three CC sections studied. For the intact hemifield we found a significant correlation between PT values and visual detection/discrimination accuracy. For the blind hemifield the level of perceptual awareness correlated with PT values for all three CC sections in the movement task. Importantly, significant differences in all three CC sections were found also between patients with above-vs. chance detection/discrimination performance while differences in the genu were found between patients with and without perceptual awareness. Overall, our study provides evidence that the properties of CC fibers are related to the presence of unconscious stimulus detection/discrimination and to hints of perceptual awareness for stimulus presentation to the blind hemifield. These results underline the importance of information exchange between the damaged and the healthy hemisphere for possible partial or full recovery from hemianopia.
摘要：
皮质盲患者存在无意识的视觉触发行为(例如，同义偏盲）已经得到了充分的证明，并且已经对这种现象的神经基础进行了彻底的研究。然而,到目前为止，尚未考虑将两个半球之间的串扰作为无意识或部分意识视觉的可能机制。因此，这项研究的目的是评估call体（CC）的结构和功能特性之间的关系，如概率纤维束成像(PT)所示，偏盲患者在盲区的行为检测/辨别表现和知觉意识水平。12名患者用黑白视觉方波光栅在两项任务中进行了测试，一个任务是运动，另一个任务是定向。刺激被横向化到一个半区域，无论是完整的还是盲目的。对MRI数据进行PT分析，以提取沿CC的纤维特性（genu，身体,和splenium）。与没有脑损伤的对照组相比，在所研究的所有3个CC切片中,患者的FA值均较低.对于完整的半球，我们发现PT值与视觉检测/辨别准确性之间存在显着相关性。对于盲半场，感知意识的水平与运动任务中所有三个CC部分的PT值相关。重要的是,上述患者与患者之间在所有三个CC切片中也发现了显着差异机会检测/辨别表现，而在有和没有知觉意识的患者之间发现了Genu的差异。总的来说,我们的研究提供了证据，表明CC纤维的特性与无意识刺激检测/辨别的存在以及对盲区的刺激呈现的感知意识的暗示有关。这些结果强调了受损半球和健康半球之间信息交换的重要性，以便可能从偏盲中部分或完全恢复。
