Visibility, type of masking, prime duration and task as determinants of effects of masked stimuli

最近的理论认为，意识与信息的整合和可获得性有关。由此推论，精神功能是存在的，当意识受损时，这些功能根本不运作，或者至少以受损的方式运作。更具体地说，简单(非整合)刺激特征的加工应该独立于意识，而复杂(整合)特征的语义加工应该随着对刺激的意识的增加而增加。一系列实证报告支持这一观点。因此，早期的知觉或运动启动效应并不依赖于最高可见度，而语义启动效应似乎依赖于最高可见度。然而，在许多研究中，质数可见度的操纵与质数的持续时间被混淆了，因为素数持续时间短和长的试验分别被比较为无意识和有意识的情况。此外，语义研究最常使用的是模式掩蔽，这可能会在启动效应和最佳可见性之间产生人为的关联。在使用元对比掩蔽的研究中，运动启动效应和可见性的独立性经常被报道。事实上，我们的初步研究表明，当使用模式掩蔽时，语义和运动启动效应取决于最高可见度，而不是元对比掩蔽。除此之外，启动效果和主可见度之间的关系也可能取决于产生启动效果所需的启动处理。计划中的项目包括13个实验，系统地比较了三种不同的掩蔽程序(模式掩蔽、元对比和拥挤)在不同任务中使用相同刺激时的效果。在每个实验中，初级能见度因特定类型的面具而有所不同，但具有不同的掩蔽强度，并记录启动效果和可见度之间的关系。如果某项任务中启动的加工依赖于启动的意识，那么启动效应也应该依赖于启动可见性。为了也掌握不连续的关系，给予素数以产生其影响的时间是不同的。功能磁共振成像被用来检查视觉层次结构中较晚处理水平的起始诱导的皮质激活是否由所使用的掩蔽程序的类型系统地确定。通过这种方式，可以直接研究掩蔽刺激在大脑中的作用范围和掩蔽轨迹。该项目的研究有助于限制对意识功能的探索，提高我们对启动效应产生机制和不同类型的掩蔽效应的理解。

Recent theories state that consciousness is related to the integration and accessibility of information. From this it follows that mental functions exist which do not operate at all or at least operate in an impaired way when consciousness is impaired. More specifically, processing of simple (non-integrated) stimulus features should be independent from consciousness whereas semantic processing of complex (integrated) features should increase with an increasing consciousness of the stimuli. A series of empirical reports support this view. Thus, early perceptual or motor priming effects do not depend on the prime visibility whereas semantic priming effects seem to depend on prime visibility. However, in many studies the manipulation of prime visibility has been confounded with the duration of the primes because trials with short and long prime durations have been compared as unconscious and conscious conditions, respectively. Additionally, semantic studies most often used pattern masking which might produce an artificial correlation between priming effects and prime visibility. Independence of motor priming effects and visibility has been reported frequently from studies that used metacontrast masking. And indeed, our pilot studies show that semantic and motor priming effects depend on prime visibility when pattern masking is used, but not with metacontrast masking. Beyond this, the relation between priming effects and prime visibility could also depend on the processing of the primes which is needed to generate priming effects. The planned project comprises 13 experiments which systematically compare the effects of three different masking procedures (pattern masking, metacontrast, and crowding) when the same stimuli are used in different tasks. Within each experiment, prime visibility is varied by masks of a specific type but with different masking strength and the relationship between priming effects and visibility is recorded. If the processing of the primes in a certain task depends on consciousness of the primes the priming effect should also depend on prime visibility. To grasp also discontinuous relationships, the time that is given to the prime to generate its effects is varied. Functional magnetic resonance imaging is used to examine whether the prime induced cortical activation at later levels of processing in the visual hierarchy is systematically determined by the type of masking procedure used. In this way the expansion of the effects of masked stimuli in the brain and the loci of masking can be directly investigated. The studies of this project contribute to confine the search for the function of consciousness and to improve our understanding of the mechanisms that produce priming effects and the different types of masking effects.