Qualitative individual differences in metacontrast masking: An instrument to investigate mechanisms of visual consciousness.

导致对视觉刺激产生有意识的主观体验的条件是当前有意识知觉研究的重点。在过去的几年里，我们采用了元对比掩蔽作为一种范式来研究有助于视觉刺激体验的过程。目前对超对比掩蔽的大多数解释都假设了一种或两种机制。我们发现被掩盖的目标刺激的可见性存在个体差异，并利用这一事实来研究有助于在后对比掩蔽中感知的机制。我们最初的研究提供了证据，证明在这种范式中，至少有三个过程是不同意识体验的基础。然而，我们最近的研究指出，参与者可以在元对比掩蔽中可靠地区分至少七种不同的主观感知。有趣的是，大多数这些感知都显示出一种清晰的时间动态，这种动态在受试者之间非常相似。基于感知经验必须由某些（神经）过程产生的假设，这些数据表明，超过两三个过程有助于形成元对比掩蔽。这里提出的建议包括两个进一步的研究，我们认为有必要成功地完成目前所做的项目。在第一项研究中，我们想要检验两个表现出相同时间动态但质量不同的感知是否实际上相互依赖，这将指向一个共同的生成过程。在第二个实验中，我们想利用受试者在相同刺激下报告两种质量不同的感知这一事实，通过比较具有相同刺激和不同主观体验的试验来识别这些主观体验的电生理特征。这个实验既可以回答每个知觉是否有自己的产生过程的问题，也可以回答关于视觉刺激的有意识主观体验的时间和地形特征的问题。

The conditions that lead to a conscious subjective experience of visual stimuli are in the focus of current research on conscious perception. In the last years we have employed metacontrast masking as a paradigm to examine the processes that contribute to the experience of visual stimuli. Most current accounts of metacontrast masking assume one or two mechanisms. We found individual differences in visibility of the masked target stimulus and took advantage of this fact to examine the mechanisms that contribute to perception in metacontrast masking. Our initial studies provided evidence for the contribution of at least three processes underlying the different conscious experiences in this paradigm. However, our more recent studies point to a number of at least seven qualitatively different subjective percepts that participants can reliably distinguish in metacontrast masking. Interestingly, most of these percepts show a clear temporal dynamic that is very similar across subjects. Based on the assumption that the experience of a percept has to be generated by some (neural) processes, these data suggest that more than two or three processes contribute to metacontrast masking. The here presented proposal comprises two further studies that we deem necessary to successfully complete the project done so far. In the first study we want to examine whether two percepts that show the same temporal dynamic but differ in quality do in fact depend on each other, which would point to a common generating process. In the second experiment we want to take advantage of the fact that subjects report two qualitatively different percepts in trials with identical stimulation to identify the electrophysiological signature of these subjective experiences by comparing trials with identical stimulation and different subjective experiences. This experiment could contribute both to the question whether each percept has its own generating process and to issues regarding the time and topographical signature of conscious subjective experiences of visual stimuli.