An ever-growing body of literature indicates that the segregation of neural processing into specialized neural regions is an essential aspect of cerebral organization. However, the integrative, multi-modal nature of cognitive processes which occur within the realm of conscious awareness appear to require a functional architecture which overcomes this modular segregation of function. We present a model which attempts to span this dichotomy, proposing that conscious experience emerges from the dynamic interactions of specialized component processes via a distributed neuronal network. Such a model offers a promising mechanism to explain a variety of empirical observations of the neural correlates of perceptual awareness, cognitive function, and symptoms of neurological damage.
The processing of emotion-laden information is often described as “automatic”, namely, independent of attention and even visual awareness. In a series of studies we have sought to carefully test this idea with both behavioral and fMRI methods. Our findings do not favor the “automaticity” assumption and, instead, reveal that both attention and task relevance (whether a stimulus was a target or a distractor) strongly modulate responses evoked by emotional faces. In more recent studies we have investigated the neural correlates of near-threshold emotional perception. Unlike previous studies, we did not find evidence for differential responses to masked fearful faces. In addition, responses were reliably driven by the subject’s percept, and less so by the physical stimulus per se – this was the case even in the amygdala. Finally, we will present recent results on the neural correlates of perceptual decision making while subjects performed difficult detection and discrimination tasks. Collectively, these studies show that while emotional stimuli may comprise a privileged stimulus category, their processing is highly dynamic and depends on the interplay of a host of factors that sculpt the associated neural responses, including task context, attention, awareness, and perceptual interpretation./p>
What is it like to be a baby? I will suggest that neurological and psychological
findings can provide insight into infant phenomenology. In adults we see an association
between vivid consciousness, plasticity and attention. In the adult system this
attention is typically focused on a small part of the external or internal world
and involves inhibition of consciousness of other parts of the world. I will
suggest that infants have a similar vivid phenomenology, also associated with
plasticity, but that it is distributed across their entire field and does not
lead to inhibition. This state may be similar to certain meditative states.
Recent advances in brain imaging have given psychologists and neuroscientists unprecedented access to the inner workings of the human mind. Because brain imaging techniques can probe representations without relying on verbal report or overt behavior, they can reveal the unconscious percepts, thoughts, memories, and emotions that influence our thoughts and actions. My lab has used such techniques to characterize high-level perceptual processing without awareness. We are also interested in the factors that govern when perceived events become encoded into conscious and unconscious memory.
Defining the extent of unconscious processing is an important step for our understanding of consciousness. It is usually assumed that conscious and unconscious perception should be explicitly distinguished. However, several studies suggest that this distinction should be abolished. In particular, studies of subliminal priming have argued that a masked stimulus can reach the highest levels of processing. In this talk, I will focus on whether there are limits to unconscious perception. I will present several behavioral and brain imaging studies aimed at characterizing the depth of processing associated with unconscious stimuli. I will present the patterns of neural activity associated with subliminal priming in several domains (written words, faces, speech) and how they differ from those induced by visible stimuli. In addition, I will present evidence for an intermediate, preconscious level of processing in which stimuli receive deeper processing compared to subliminal perception, but remain unavailable for conscious report. I will argue not only that the distinction between conscious and unconscious processing should be maintained, but also that it should include an intermediate preconscious step. I will explain why maintaining this taxonomy is essential in order to make sense of the growing neuroimaging data on the neural correlates of consciousness.
It is plain that an individual's being conscious and an individual's being
conscious of various things are both crucial for successful functioning. But
it is far less clear how, if at all, it is also useful for an individual's
psychological states to occur consciously, as against their occurring but
without being conscious. Restricting attention to cognitive and desiderative
states, a number of suggestions are current about how the consciousness of
those states may be useful. It has been thought that such consciousness enhances
processes of rational thought and planning, intentional action, executive
function, and the correction of complex reasoning. I examine these proposals
in the light of various empirical findings and theoretical considerations,
and conclude that the consciousness of cognitive and desiderative states is
unlikely to be useful in these or related ways. This undermines a reliance
on evolutionary selection pressures in explaining why such states so often
occur consciously in humans. I briefly conclude with an alternative explanation,
on which cognitive and desiderative states come to be conscious as a result
of other highly useful psychological developments involving language use.
But on this explanation the consciousness of these states adds no significant
functionality to that of those other developments.