Investigation of Visual awareness and its neural mechanism in macaque model of blindsight

据报道，V1单侧病变的猕猴表现出与人类盲视患者相似的行为（Cowey和Stoerig，1995）。在这里，我们研究了单侧V1病变的猴子使用扫视任务的视觉意识的行为报告，并寻求特定于盲视的神经活动。首先，我们研究了猴子是否能够维持短期记忆的刺激呈现在他们的对侧（受影响）hemifield。这些猴子被测试了一个记忆引导的扫视任务，延迟2秒。成功率超过80%，明显高于偶然。然后，我们记录了在记忆引导的扫视任务中上级丘（SC）的神经元活动。我们发现，大多数记录自同侧SC的神经元表现出对目标空间位置的选择性延迟活动。另一方面，在对侧损伤的SC中，具有延迟活动的神经元的比例较低。 ...更多信息 V1损伤的猴子保留了一定水平的视觉意识，并且在SC中表现出来。然后，我们通过比较强迫窒息（FC）任务的表现，更直接地检查了它们的视觉意识。其中需要定位目标位置，以及其中需要检测目标的是非（YN）任务。当刺激呈现在受影响的半野时，FC任务的表现优于YN任务。当在同侧（“正常”）半视野中呈现具有低亮度对比度的刺激时，没有观察到这种解离和表现，这表明解离是特定于V1病变的，而不是发生在近阈值视觉中的一般现象。然后我们研究了在YN任务中SC的神经活动是否依赖于猴子对视觉意识的报告。我们发现，在同病灶SC，在受影响的半野的视觉刺激的神经反应较大时，猴子成功地检测到的目标比当猴子错过了他们。这种调制没有发现在正常hemifield的近阈值刺激的神经反应时，我们记录从contralisional SC。这些结果表明，调制的神经活动中发现的isilisional SC是一个神经相关的视觉意识降低，具体引起V1病变。少

It has been reported that macaque monkeys with unilateral lesions in V1 exhibited analogous behavior to the human blindsight patients (Cowey and Stoerig, 1995). Here we examined behavioral report of visual awareness in monkeys with unilateral V1 lesions using saccade tasks and sought neural activity specific to blindsight. First, we examined whether the monkeys are able to maintain short-term memory of the stimuli presented in their contralateral (affected) hemifield. The monkeys were tested with a memory-guided saccade task with a 2 sec-delay. The success ratio was over 80%, significantly higher than chance. Then we recorded the neuronal activity from the superior colliculus (SC) during the memory-guided saccade task We found that a majority of the neurons recorded from the ipsilesional SC showed a delay activity selective for spatial locations of targets. On the other hand, the ratio of neurons with a delay activity was lower in the contralesional SC. These results suggest that the m … More onkeys with V1 lesion retain a certain level of visual awareness and that it was represented in the SC. Then we examined their visual awareness more directly using comparison between the performance of a forced-choke (FC) task., in which localization of target positions was required, and that of a yes-no (YN) task, in which detection of the targets was required. The performance of the FC task was better than that of the YN task when stimuli were presented in the affected hemifield. Such a dissociation &performance was not observed when stimuli with low luminance contrasts were presented in the ipsilateral ('normal') hemifield, indicating that the dissociation is specific to the V1 lesion, not a general phenomena occurring in near threshold vision. Then we examined whether the neural activity of SC during the YN task is dependent on the monkeys' report on visual awareness. We found that, in the ipsilesional SC, the neural response to the visual stimuli in the affected hemifield was larger when the monkeys successfully detect the targets than when the monkeys missed them. Such modulation was not found in the neural response to the near threshold stimuli in the normal hemifield when we recorded from the contralesional SC. These results suggest that the modulation of neural activity found in the ipsilesional SC is a neural correlate of reduced visual awareness that specifically induced by V1 lesion. Less