Traditional ways to examine and investigate the neural correlates of consciousness usually require the participants to actively report their perceptions and conscious contents. Having the participants actively report can confound the neural correlates with co-occurring processes. Instead, no-report paradigms try to remove the active process of reporting by either objectively trying to measure conscious content by tracking eye movements and pupil dilation, or retroactively inquire about the conscious states. The results of an fMRI experiment utilising tracking of optokinetic nystagmus and pupil dilation as an objective measure of conscious content highlight a difference in frontal areas while activation in posterior areas are similar to active report experiments. EEG experiments utilising the sustained inattentional blindness paradigm did not see the late positivity commonly seen when the participants were aware of the stimuli but it was not task relevant. Utilising no-report paradigms can provide unique insights into the discussion of theories of consciousness and further develop our understanding of consciousness.

The philosophical and scientific studies of consciousness are two disciplines having much to learn from one another. On the one hand, a science of consciousness involves taking an objective approach to what is essentially a subjective phenomenon, giving rise to tricky conceptual and methodological issues, ones an analytic philosopher is perhaps best equipped to handle. On the other hand, a wealth of data now exists concerning the neural basis of consciousness. Such data, interpreted properly, can confirm or disconfirm philosophical views on consciousness, helping adjudicate debates thus far intractable. This dissertation explores some ways in which the philosophy and science of consciousness can be of mutual benefit to one another.

Two theories of consciousness have different ideas about when consciousness happens and what neural processes enable conscious experience. The recurrent processing theory supports an early onset of consciousness caused by recurring loops of information between sensory areas. Contrary to this belief, the global workspace theory claims that consciousness appears later, through global recurrent loops of information between sensory and higher order brain areas such as the visual cortex and frontoparietal areas. Electrophysiological studies have found an event-related negativity arising in primary visual areas around 200 ms that correlates to awareness. This activity suits the predictions of an early onset of consciousness made by the recurrent processing theory. It is followed by a later positive amplitude appearing around 400 ms. This activity is in line with predictions made by the global workspace theory. The current study transition from visual to auditory awareness research in order to find the neural correlates of consciousness in audition. A sound detection task with tones calibrated to each participants threshold value was used in the experiment and two electrophysiological measurements of auditory awareness were found. An auditory awareness negativity that appears around 200 ms after stimulus onset and a late positivity appearing around 400 ms. Researchers disagree about if these event-related potentials correlate with awareness or unrelated cognitive mechanisms. In order to solve this problem, the current experiment was devised to test if they were affected by response conditions. A no-response paradigm with reversed response conditions was used to separate pre- and post-conscious mechanisms from the auditory awareness negativity and the late positivity. Results showed that auditory awareness negativity was independent of response condition and thus free from post-perceptual processes. The late positivity amplitude seems to be dependent on response condition but the result was inconclusive.

Two decades of event-related potential (ERP) research have established that the most consistent correlates of the onset of visual consciousness are the early visual awareness negativity (VAN), a negative component in the N2 time range over posterior electrode sites, and the late positivity (LP), a positive component in the P3 time range over fronto-parietal electrode sites. A review by Koivisto & Revonsuo (2010) had looked at 39 studies and concluded that the VAN is the earliest and most reliable correlate of visual phenomenal consciousness, whereas the LP probably reflects later processes associated with reflective/access consciousness. However, an “early” vs. “late” debate still persists. This thesis provides an update to that earlier review. All ERP and MEG studies that have appeared since 2010 and directly compared ERPs of aware and unaware conditions are considered. The result corroborates the view that VAN is the earliest and most consistent signature of visual phenomenal consciousness, and casts further doubt on the LP as an ERP correlate of consciousness. Important new methodological, empirical, and theoretical developments in the field are described, and the empirical results are related to the theoretical background debates.

Die sensorischen Informationen, die uns jederzeit zur Verfügung stehen, sind umfangreich, doch unsere bewusste Wahrnehmung erfasst nur einen kleinen Teil davon. Welche Faktoren entscheiden, welche Informationen bewusst wahrgenommen werden? Wie gestaltet sich der Übergang von unbewusster zu bewusster Verarbeitung? Diese Dissertation untersucht den Zugang visueller Informationen zur bewussten Wahrnehmung unter reduzierter Aufmerksamkeit sowie den Einfluss sozial-emotionaler Faktoren. In den Studien wurden Gesichter, die sich in ihrer wahrgenommenen Vertrauenswürdigkeit unterscheiden („Facial Trustworthiness“), mit negativem oder neutralem sozialem Wissen verknüpft und in einer Attentional-Blink-Aufgabe präsentiert. Studie 1 analysierte die Auswirkungen von affektivem Wissen und äußerlichen Merkmalen auf Verhaltensebene, während Studien 2 und 3 neuronale Prozesse mithilfe ereigniskorrelierter Potenziale (EKPs) untersuchten. Die Ergebnisse von Studie 2 zeigten einen graduellen Übergang zur bewussten Wahrnehmung, erkennbar an abgestuften Sichtbarkeitsbewertungen, der Aufgabenleistung und der Aktivität spezifischer EKP-Komponenten (N1-, N2- und P3-Komponenten). In den Studien 1 und 3 wurde eine verstärkte Wahrnehmung von Gesichtern festgestellt, die mit negativem Wissen assoziiert waren, während keine Effekte der Facial Trustworthiness nachgewiesen wurden. Der Einfluss affektiven Wissens war neurophysiologisch mit Unterschieden in der Early Posterior Negativity (EPN) verknüpft – einer Komponente, die mit erhöhter Aufmerksamkeit auf emotionale Reize assoziiert ist. Zusammenfassend stellt diese Arbeit das Konzept des Attentional-Blink als Alles-oder-Nichts-Phänomen infrage und legt nahe, dass graduelle Unterschiede in der bewussten Wahrnehmung bestehen. Sie liefert zudem Einblicke in den zeitlichen Verlauf und die Charakteristiken sozial-emotionaler Einflüsse auf die Wahrnehmung. Diese Befunde werden im Kontext aktueller Bewusstseinsforschung diskutiert. / The sensory information available to us at any given moment is extensive, yet our conscious perception only encompasses a fraction of it. What factors determine which information enters our conscious awareness? How is the transition from unconscious to conscious processing structured? This dissertation examines the access of visual information to conscious perception under conditions of reduced attention and the influence of socio-emotional factors. In the present studies, faces varying in perceived trustworthiness based on appearance (“facial trustworthiness”) were associated with negative or neutral social knowledge and presented in an attentional blink task. Study 1 analyzed the effects of affective knowledge and facial appearance on behavioral responses, while Studies 2 and 3 investigated neural processes using event-related potentials (ERPs). The results of Study 2 revealed a gradual transition to conscious perception, as reflected in graded visibility ratings, task performance, and ERP activity (N1, N2, and P3 components). Studies 1 and 3 found enhanced perception of faces associated with negative knowledge, while no effects of facial trustworthiness were observed. On a neurophysiological level, the influence of affective knowledge was linked to differences in the early posterior negativity (EPN), a component associated with increased attention to emotional stimuli. In summary, this work challenges the concept of the attentional blink as an all-or-nothing phenomenon and suggests the existence of graded differences in conscious perception. It further provides insights into the temporal dynamics and characteristics of socio-emotional influences on perception. These findings are discussed in the context of current consciousness research.