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

据报道，单侧V1区损害的猕猴表现出与人类盲人相似的行为(Cowey和Stoerig，1995)。在这里，我们使用眼跳任务检查了单侧V1损伤的猴子的视觉意识的行为报告，并寻找了盲目特有的神经活动。首先，我们检查了猴子是否能够保持对其对侧(受影响的)半脑的刺激的短期记忆。这些猴子接受了一项记忆引导的眼跳任务，测试时间为2秒。成功率在80%以上，明显高于机率。然后，我们记录了记忆引导的眼跳任务中上丘(SC)的神经元活动，我们发现从自体SC记录到的大部分神经元表现出对目标的空间位置有选择性的延迟活动。另一方面，对侧SC中延迟活动的神经元比例较低。这些结果表明，m…更多患有V1病变的猴子保留了一定程度的视觉意识，并在SC中表现出来。然后，我们通过比较强迫窒息(FC)任务和是-否(YN)任务的表现，更直接地检验了他们的视觉知觉。在FC任务中，需要定位目标位置，而在YN任务中，需要检测目标。当刺激出现在患侧时，FC任务的成绩要好于YN任务。当低亮度对比度的刺激出现在同侧(‘正常’)半视野时，没有观察到这样的分离和表现，这表明这种分离是V1损伤所特有的，而不是在接近阈值的视觉中发生的普遍现象。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知觉的报告。我们发现，在单侧SC中，当猴子成功探测到目标时，受累半球对视觉刺激的神经反应比猴子错过目标时更大。当我们从对侧SC记录时，在正常半球对近阈值刺激的神经反应中没有发现这种调制。这些结果表明，损毁SC中神经活动的调节与V1损毁引起的视觉知觉减退有关。较少

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