ASSC 14

SYMPOSIUM 1

Conscious Awareness, Perceptual Decision making & the Bayesian Brain

Chair: Hakwan Lau (Columbia University, USA)

Speakers: Stanislas Dehaene (College de France, FRANCE)
Hakwan Lau (Columbia University, USA)
Imogene Dickie (University of Toronto, CANADA)
Ned  Block (New York University, USA)

Summary: There is a long tradition in psychophysics to characterize perception as a decision process. This is because neurons are noisy, and in the face of uncertainty the brain must "decide" what is the object of perception, based on imperfect information. One idea that has recently gained popularity is the Bayesian Brain Hypothesis, which states that the brain takes into account the uncertainty and makes optimal decisions based on probability theory. What does this mean for consciousness? Do these ideas apply equally to conscious and unconscious perception? What are the possible differences? One possibility could be that conscious perception is based on decisions with strong signals and high certainty. Alternatively, it could be that conscious perception depends on sensory evidence from specific channels; other channels contributes to the decision process but cannot yield conscious awareness. Two cognitive neuroscientists (Dehaene and Lau) present brain stimulation, imaging and lesion data to argue for these different models. Some of the models make use of modern computational concepts and can account for the fine-grained dynamics of perception (diffusion models). Arbitrating between these models may prove crucial to theoretical development. E.g. some models support the higher-order representational theory, whereas others don't. These new exciting ideas from neuroscience may also have interesting philosophical implications. E.g. if perception is to be considered as a decision making process, perhaps consciousness could be considered as the "justification" of the perceptual decision. Two philosophers (Dickie and Block) discuss and elaborate on these ideas.

SYMPOSIUM 2

Possible Contributions of Research on Meditation to the Neuroscience of Consciousness

Chair: Antoine Lutz (University of Wisconsin, USA)

Speakers: John D. Dunne (Emory University, USA),
Antoine Lutz (University of Wisconsin, USA),
Heleen Slagter (University of Amsterdam, The Netherlands)

Summary: Various meditative practices induce a wide variety of altered states of consciousness.  It is thus frequently claimed that the study of meditation will contribute to our general understanding of the neural basis of consciousness. This symposium aims to move beyond this general claim and illustrate how specific Buddhist practices might provide research opportunities to glean new insights about some of the brain mechanisms contributing to consciousness. More precisely, this symposium aims at (1) defining meditation as a scientific explanandum, (2) proposing a theoretical framework, based on traditional meditation texts and modern neuroscientific conceptions of some standard meditation practices, and (3) illustrating the usefulness of meditation as a tool in the neuroscientific study of consciousness using empirical data. The symposium will in particular address how meditation is of great interest in the study of a) the physical substrate of subjectivity or the self; b) the functional role of the spontaneous brain baseline; and c) the relationship between attention and awareness. This symposium brings together researchers who have examined meditation from the view point of Buddhist epistemology and phenomenology, and cognitive neuroscience.

SYMPOSIUM 3

Mechanisms in crowding and blink: what can they tell us about consciousness?

Chair: Ramakrishna Chakravarthi (CNRS -, FRANCE)

Speakers: Jeremy Freeman (New York University, USA)
Timothy Vickery (Yale University, USA)
Ramakrishna Chakravarthi (CNRS -, FRANCE)  
Mark Nieuwenstein (University of Groningen, The Netherlands)

Summary: Our conscious experience involves the perception of a rich visual world. A central part of this experience is our ability to effortlessly isolate and recognize objects in a given scene. Visual crowding is a dramatic breakdown of this object recognition process. An otherwise easily identifiable object is rendered unidentifiable if it is surrounded by other objects. In this phenomenon, the observer can clearly detect the presence of a target object, yet its identity never reaches awareness. This is true even if the observer is allowed to view the scene or attend to the target location for an indefinite period of time. Similarly, if a target is surrounded temporally by other targets, it becomes hard to identify. Determining the causes for this blockage can provide a window into the necessary conditions for the awareness of object identity. This symposium explores the underlying mechanisms of crowding and related phenomena such as attentional blink and delves into their implications for visual consciousness research. Timothy Vickery will present evidence for supercrowding, where object features are forced to combine over extremely large distances both in the periphery and the fovea. Mark Nieuwenstein will discuss the causes and implications of attentional blink. Finally, Jeremy Freeman will describe a computational combined with a uniquely ‘visual’ approach to crowding and visual perception.

SYMPOSIUM 4

Neurophysiological approaches within the scientific study of consciousness

Chair: Alexander Maier (NIH, Bethesda, USA)

Speakers: Alexander Maier (NIH, Bethesda, USA)
Naotsugu Tsuchiya, (Caltech, USA & Tamagawa University, Japan)
Melanie Wilke (Caltech, USA)

Summary: The study of brain activity is a cornerstone for constructing and testing scientifically founded theories of consciousness.  Non-invasive imaging techniques such as fMRI and MEG have become invaluable research tools, but they often stop short due to their limited space- and time resolution.  Some of these limitations can be overcome by measuring neuronal activity with probes that penetrate the skull.  We will discuss how invasive neurophysiological techniques can help answer fundamental questions in the scientific study of consciousness, such as: Is activity in the face-sensitive cortex necessary and sufficient for producing the subjective experience of a face? What kind of neuronal activities are correlated with the construction of a conscious visual percept?  Is activity in primary sensory areas correlated with the conscious percept?  Is the interaction between the thalamus and the cortex necessary and sufficient for having conscious experience? And, are attention and awareness just two different aspects of the same neural processes, or are they the products of separate neural circuits?  Our symposium focuses on the relationship between neural processing and the contents of consciousness by exploring the neuronal underpinnings of perceptual experience. Towards this aim, each speaker will present empirical findings from electrophysiological recordings in trained monkeys or human epileptic patients. Following the talks, the session will be wrapped up with a brief discussion on the benefits of intracranial recordings for the search of neural correlates of consciousness.