Patients with blindsight are blind due to an early visual cortical lesion, but they can discriminate stimuli presented to the blind visual field better than chance. Studies using transcranial magnetic stimulation (TMS) of early visual cortex have tried to induce blindsight-like behaviour in neurologically healthy individuals, but the studies have yielded varied results. We hypothesized that previous demonstrations of TMS-induced blindsight may result from degraded awareness of the stimuli due to the use of dichotomous visibility scales in measuring awareness. In the present study, TMS was applied to early visual cortex during an orientation discrimination task and the subjective scale measuring awareness was manipulated: The participants reported their conscious perception either using a dichotomous scale or a 4-point Perceptual Awareness Scale. Although the results with the dichotomous scale replicated previous reports of blindsight-like behaviour, there was no evidence of TMS-induced blindsight for orientation when the participants used the lowest rating of the 4-point graded scale to indicate that they were not aware of the presence of the stimulus. Moreover, signal detection analyses indicated that across participants, the individual’s sensitivity to consciously discriminate orientation predicted behaviour on reportedly unconscious trials. These results suggest that blindsight-like discrimination of orientation in neurologically healthy individuals does not occur for completely invisible stimuli, that is, when the observers do not report any kind of consciousness of the stimulus. TMS-induced blindsight for orientation is likely degraded conscious vision.

盲视患者由于早期视觉皮层病变而失明，但他们比偶然更能区分呈现给盲人视野的刺激。使用早期视觉皮层的经颅磁刺激 (TMS) 的研究试图在神经系统健康的个体中诱导类似盲视的行为，但这些研究产生了不同的结果。我们假设之前的 TMS 诱导的盲视演示可能是由于在测量意识时使用二分能见度量表而导致对刺激的意识下降。在本研究中，TMS 在方向辨别任务期间应用于早期视觉皮层，并操纵测量意识的主观量表：参与者使用二分量表或 4 点感知意识量表报告他们的意识感知。尽管二分法的结果复制了之前关于盲视行为的报告，但当参与者使用 4 点分级量表的最低评分来表明他们不知道 TMS 引起的定向盲视时，没有证据刺激的存在。此外，信号检测分析表明，在参与者之间，个体对有意识区分方向的敏感性预测了据报道的无意识试验的行为。这些结果表明，对于完全不可见的刺激，即当观察者没有报告任何类型的刺激意识时，神经系统健康个体中的类似盲视的方向歧视不会发生。TMS 引起的定向盲视可能是意识视力下降。