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Following up on the highly successful experiences of previous ASSC conferences,
ASSC4 will again be preceded by a full day of workshops designed to allow researchers and students alike to gain a background in
potentially relevant areas that they may know little about.
Each workshop is intended to last approximately three hours. The sizes of workshops will vary between a
minimum of 10 to a maximum of around 25 people, thus enabling close interaction between workshop presenters and participants.
For further information about workshops, please contact the workshop coordinator, Patrick Wilken: patrickw@cs.monash.edu.au.
To register for one or (maximum) two workshops, please see the registration pages.
| W01 |
Chris Frith & Geraint Rees:
On the Use of Brain Imaging to Study the Neural Correlates of Consciousness
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In this workshop we will:
- Describe the principles of the four main brain imaging techniques: EEG,
MEG, PET, fMRI
- Describe the theoretical and practical limitations of these techniques
with particular reference to the environment in which experiments must be
conducted and the measures that can be derived.
- Provide a framework for conducting brain imaging studies that distinguish
neural correlates of consciousness from neural activity that is not related
to consciousness and to provide examples of experimental designs that have
been used for this purpose.
Further information and papers for further reading can be found at:
http://www.fil.ion.ucl.ac.uk/groups/Frith.main.html
http://www.klab.caltech.edu/~geraint/
Chris Frith - University College London
Geraint Rees - California Institute of Technology
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| W02 |
Paul J. Reber & Ken A. Paller:
Neural Correlates of Conscious and Nonconscious Memory
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One particularly fruitful way to try to understand the contrast between
conscious and nonconscious processing has been to study dissociations in
memory functions.
Evidence for distinct neural substrates for two
types of memory, declarative and nondeclarative, has been principally
drawn from a large number of studies of patients with memory disorders
due to neurological damage. Measuring the activity of the human brain
can provide many clues about the neurophysiological mechanisms
responsible for conscious and unconscious memory. In particular, the
subjective experience of remembering appears to be closely associated
with the ability to recall and recognize facts and events, often termed
declarative or explicit memory. This workshop will consider a rapidly
growing body of investigations using ERPs and fMRI to explore brain
mechanisms of multiple forms of memory and consciousness. Evidence that
patterns of neural activity associated with conscious and nonconscious
memory can be differentiated not only reinforces the neuropsychological
dissociations but is also helpful for generating and testing new
hypotheses about the operation of these types of memory. This work may
thus lead to a better understanding of the enigmatic border between
conscious and unconscious memory. The application of neuroimaging
techniques to the study of memory systems should also serve to
illustrate how neuroscientific study of the brain can provide insight
into cognitive phenomena that are associated with conscious and
nonconscious processing.
Paul J. Reber - Northwestern University
Ken A. Paller - Northwestern University
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| W03 |
Thomas Metzinger & Andreas Engel:
Constraining Consciousness: Towards a Systematic Catalogue of Explananda
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From a methodological point of view, the newly emerged field of
consciousness research has two main characteristics. First, it is currently
in a 'preparadigmatic' stage: There is no single,
comprehensive theory of consciousness in existence, which could function as
a unified background for research or as a shared departure point for
constructive criticism. Second, there is no accepted canon of explananda: We
still don't have a systematic catalogue of what it is that is to be
explained, a clear and rigorous list of research targets, which can be
continuously refined and developed as work progresses. Therefore, the
process of hypothesis generation takes place in a completely unsystematic manner. This workshop
will make a first attempt of tackling the second problem, adopting a
"theory-of-science" stance to the field.
Hour One (Thomas Metzinger):
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Analysanda and explananda: Conceptual and empirical aspects.
- The four main levels of description: Conscious systems and their
properties under phenomenological, representationalist, functionalist and
neuroscientific descriptions. Conscious experience as a "level of
organization".
- Six examples for fundamental constraints on the phenomenological level of
description. Methodological issues concerning the epistemic asymmetry,
ineffability and perspectivalness.
- Developing constraints on the representationalist level of description
(current philosophical ideas about the "hegemony of representation").
The notion of "phenomenal content", and the strategy of developing a
representationalist analysis of specific types
of phenomenal content.
Hour Two (Andreas Engel):
- Developing constraints on the functional and physiological levels of
description: Potential explananda at the neurobiological level and goals of
a theory of the NCC.
- Components of the NCC. Discussion of a tentative list of relevant neural
processes. These include arousal, sensory segmentation, attentional, working
memory, all of which seem required for sensory awareness as a basic form of
consciousness, as well as processes like motivation, action planning,
declarative memory and, in humans, symbol processing. It will be suggested
that, from the viewpoint of contemporary empirical research, all items on
this list must be envisaged as genuine explananda for future research, since
for all these physiological processes current theories are, at best,
incomplete.
- From correlation to explanation. Examples will be discussed for
neurobiological evidence relating to basic mechanisms of conscious
awareness. It will be suggested that for many of the processes listed above,
binding mechanisms are required. Any consciousness theory must account for
how activity in multiple neural modules can be integrated and how
large-scale coherence can emerge within distributed neural systems.
Furthermore, such a theory must specify mechanisms for the dynamic selection
of subsets of neuronal responses, since only a fraction of all available
information gains access to consciousness. We will propose that both
requirements, cross-systems coherence and dynamic response selection, can be
met by one and the same binding mechanism based on the synchronization of
neuronal discharges. Recent evidence from both animal and human studies
supports this hypothesis, demonstrating that neuronal synchrony covaries
with perceptual integration, buildup of coherent representations,
attentional selection, and awareness. These data suggest that
synchronization, particularly if accompanied by fast oscillations in the
gamma-frequency band, may be one of the necessary conditions for the
emergence of conscious mental states.
Hour Three (Andreas Engel & Thomas Metzinger):
- Discussion with participants: potential relevance of physiological
mechanisms for a (1) 'access conscious' states, and (2) for constraining a
representational theory of phenomenal consciousness.
- Discussion with participants: Directions for future research (e.g. role
of animal models in NCC research, optimizing interdisciplinary cooperation,
etc.). Necessary steps towards a systematic research program for
consciousness.
Materials will be provided.
Thomas Metzinger - Universität GH Essen
Andreas K. Engel - Max-Planck-Institüt für Hirnforschung
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| W04 |
Jonathan Cole, Natalie Depraz & Shaun Gallagher:
Unity and Disunity in Bodily Awareness: Phenomenology and Neuroscience
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In this workshop we explore how one's body, and especially motor behavior,
shapes conscious experience. To what extent, and in what precise way is
the body present in perceptual experience? Is it possible to have a
non-perceptual present awareness of one's body? To what extent does the
unity of perceptual consciousness depend on the phenomenological
transparency of the body? How does motoric behavior, much of which is not
conscious, affect conscious experience? What is the relationship between
consciousness and gestural movement? We address these issues from several
perspectives, including:
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Phenomenology: A phenomenological approach allows us to consider issues
pertaining to body-image and to investigate the question of perceptual and
non-perceptual awareness.
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Clinical Studies: We explore the contrasting characteristics of unilateral
neglect and deafferentation. We detail one particular rare case (IW)
involving loss of proprioception and touch from the neck down.
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PET and magnetic stimulation studies: The results of PET studies of IW
involving self-movement and visual monitoring help to identify brain areas
responsible for movements under visual control and those made without
apparent feedback.
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Experimental studies: Results of experiments we conducted on IW's ability
to gesture indicate to what extent gesture depends on proprioceptive
feedback, and suggest precise conclusions concerning the relationship
between motor and communicative aspects of gestural behavior.
Outline of workshop:
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Phenomenological description of normal bodily experience. Awareness of
the body during intentional action. Perceptual and non-perceptual
awareness of the body. The status of proprioception. The distinction
between body image and body schema. Questions and Discussion.
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Empirical evidence for the distinction between body image and body
schema. The case of unilateral neglect. Loss of body image. The case of
deafferentation: IW. The effects of a loss of proprioception and touch
from the neck down. Loss of body schema. Difficulties with motor control;
the visual and cognitive monitoring of movement. Questions and Discussion.
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Results of magnetic stimulation studies of IW. Visual and imaginative
control as replacement for proprioceptive body schema. Task: small movement
of thumb; superimposed magnetic stimulation. Evidence against perception of
movement based on central corollary discharge. Questions and Discussion.
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Results of PET scans of IW. The experiment involved a simple sequential
finger/thumb apposition task. Four conditions of movement were investigated:
(a) Self-movement and visual monitoring
(b) Self-movement without visual monitoring
(c) No self-movement and visual perception of other's movement
(d) No self-movement and no visual perception of movement
By comparison of the patterns of activation within the brain
for these conditions in IW and controls conclusions may be made about
the brain areas involved in movement without peripheral
feedback. The areas activated during visual control of movement and
during movement without visual or peripheral feedback may be analysed
and from this the roles of parietal cortex and cerebellum in corollary
discharge considered. Questions and Discussion.
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Experiments on gesture. To what extent does gestural movement
depend on conscious monitoring? What does the motor system contribute to
language? Is it purely central or based on sensory feedback?
Experiments with deaf unilateral neglect patients (Bellugi and Klima
1997) and with IW show to what extent and in what way embodiment is a
necessary condition for linguistic behavior, and to what extent language
transcends embodiment and shapes our thought.
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Conclusions: The phenomenology of neglect and deafferentation as
well as the experimental results allow us to draw conclusions about the
need for body awareness during various motor tasks. Work from PET
studies suggest the brain areas involved in movements under visual
control and those made without apparent feedback. We discuss the
implications of the empirical data for the question of the unity of
consciousness, and outline a distinction between the phenomenal unity
and the prenoetic unity of consciousness.
Jonathan Cole - Southampton University
Natalie Depraz - Université de Paris
Shaun Gallagher - Canisius College
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| W05 |
David Rosenthal:
Consciousness and the Philosophy of Mind
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The workshop will provide an background overview of recent and
contemporary philosophical literature about the mind relevant to the
scientific study of consciousness.
There will be three sections, each of about an hour. The first will
provide some general background in philosophy of mind. Building on that
background, the second section will focus on specific questions about
consciousness that have figured prominently in the recent philosophical
literature. The third section will survey the major theoretical
approaches to consciousness found in that literature and perhaps explore
some connections these approaches have with empirical work about
consciousness.
I. General Background in Philosophy of Mind
Recent work in the philosophy of mind clusters around four main
questions. Two have a distinctively philosophical cast: the meta-
physical problem of the relation of mind and body and the epistemo-
logical problem of how we know about the minds of others. The other two
problems are independent of such traditional philosophical concerns:
the question of how to characterize the various types of mental
phenomena (what I'll call the "characterization problem") and of how
mental phenomena figure in psychological explanation (the "explanation
problem").
All four problems are crucial for understanding current philosophical
discussions of consciousness. (1) The mind-body problem has led to
questions about whether conscious qualitative properties outstrip
physical reality (Frank Jackson's "Knowledge Argument") and David
Chalmers's "Hard Problem" about how conscious qualitative states can
occur in physical systems. (2) The other-minds problem raises issues
about the special, privileged access we seem to have to our own
conscious states. (3) The characterization problem points to the
question of whether the various kinds of mental state can occur without
being conscious and, if so, in virtue of what conscious states differ
from states that are not conscious. It also raises issues, highlighted
by Ned Block and others, about whether there are distinct, independent
properties we refer to under the heading of consciousness. (4) The
explanation problem, finally, raises Joseph Levine's question about
whether an explanatory gap separates physical processes from qualitative
consciousness, as well as the question whether consciousness has any
distinctive function.
II. Philosophical Questions about Consciousness
Building on this background, the workshop will focus on discussion in
the recent philosophical literature of four clusters of questions
specifically about consciousness.
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Are mental states all conscious? Or perhaps all qualitative
states? Or are all mental states potentially conscious, as John Searle
claims? When a mental state is conscious, is the property it has of
being conscious intrinsic to the state? Or is it something about the
way the state is related to other things?
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Is there a property of being conscious (such as Block's "phenomenal"
consciousness) that is unique to qualitative states, such as pains and
perceptual sensations? And can we characterize the qualitative
properties of sensory states independently of whether the states are
conscious? Some discussion of the alleged problems about inverted and
absent qualia may figure here.
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Is what consciousness tells us about our mental states always
correct? Is it complete? If not, how can we distinguish between our
actual mental states and those consciousness represents us as having?
Can introspective access be mistaken? Does introspection report our
mental states or interpret our mental lives?
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And on the topic of ASSC4: How are the contents of consciousness
unified? Can mental states be conscious without being thus unified with
other conscious states? What is it for a creature to be conscious, as
against a mental state's being conscious? Does a creature's being
conscious mean that its mental states are conscious? Does it mean that
its conscious states are unified? Is the unity of consciousness more
than mere appearance?
III. Theoretical Models and Research Issues
Recent discussions of consciousness in the philosophical literature fall
into two main groups: those which represent consciousness as an
intrinsic property of mental states and those which represent it as a
relation conscious states bear to something else.
Intrinsicalist views describe consciousness by way of a relatively
small circle of interdefined notions, such as subjectivity, perspective,
point of view, and the like. So these views do not lend themselves to
giving an informative, scientific account of consciousness with
empirically testable consequences. Thomas Nagel's view, on which the
subjective, perspectival character of conscious mental phenomena
precludes any objective account of their nature, is usefully seen as an
example of this kind of approach. (This is different from Colin McGinn's
view that limitations on our mental nature itself preclude our
developing or even understanding any informative account of
consciousness.)
Relational models, by contrast, readily lend themselves to empirically
testable predictions and explanations. The standard example of such a
model is the "Inner Sense" view, on which a mental state's being
conscious consists in one's sensing it. A second relational model
discussed in the recent philosophical literature is Daniel Dennett's
Multiple Drafts Model, on which consciousness is the continually revised
result of many interacting subpersonal processes. A third version is
the higher-order-thought hypothesis, on which a state's being conscious
consists in one's having a non-conscious, noninferential thought that
one is in that state.
These three models will be discussed, possibly in connection with such
topics of current empirical research as metacognition, confabulatory
introspective reports, blindsight and other dissociative disorders,
confabulatory introspective reports, and the causal efficacy of
conscious, voluntary decision. (Because our concern will be with how to
characterize consciousness, we will not address questions about the
neural correlates of consciousness.)
David Rosenthal - City University of New York
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| W07 |
Dan Lloyd:
Unity, Association, and Dissociation of Temporal Consciousness in Recurrent Neural Networks
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The unity of consciousness over time is one of the fundamental issues of
classical phenomenology. Husserl, for example, devoted much of his
Phenomenology of Internal Time Consciousness to an analysis of the
structure of the experienced now, which he noted contained within it a
retention of the past and anticipation of the future. This fundamental
aspect of consciousness studies is only indirectly treated in cognitive
science, in the study of working memory and prospective memory. This workshop
will explore topics in the underlying neural architecture of the unity of
temporal consciousness. Issues to be addressed include the following:
- What is the subjective experience of temporal unity?
- How does classical cognitivism address (or not) these experiences?
- Does connectionism, in the form of back-propagation networks, offer a
more successful program?
- Does recent connectionist work in recurrent networks (Elman 1990, 1996)
add significantly to the explanatory resources available to understand
temporal awareness?
- Finally, in this progression of approaches are there new ways to
interpret functional brain imaging as a component of consciousness studies?
The workshop will include demonstrations of several specific simulations and
analyses, including:
- Models of working memory in recurrent neural networks, based on EEG
"readiness" tasks in humans, and delayed matching tasks in humans and
monkeys. The models are readily probed by methods analogous to population
recording (EEG), "region of interest" recording (functional brain imaging),
and single unit recording. But all of these methods are overly selective and thus
distort the underlying neurodynamics. Multivariate analysis (cluster
analysis, multidimensional scaling, and principle components analysis)
affords a more comprehensive view, revealing the spontaneous emergence
of rhythms and "cell assemblies," the internal representation of
prospective and retrospective duration, and temporal categories.
- Models of dissociation following trauma. Trauma can be understood in
neural network terms as single-trial learning with an abnormally high
learning rate. This simple idea, implemented in a recurrent net, exhibits
analogues of all the DSM symptoms of post-traumatic stress disorder, and
even parallels exactly an early case history of Freud.
- Meta-Analyses of PET and fMRI data. The same techniques for multivariate
analysis used with the artificial neural networks can be applied to the
brain. Treating the brain as a distributed processor reveals underlying
organization consistent with that found in the simulations, and analogous
in many ways to phenomenological observations.
Thus, the discussion overall will explore a complex analogy across
phenomenology, connectionism, and cognitive neuroscience. We will consider
the prospects for a future "neurophenomenology," and its limits.
Workshop participants will receive complete specifications of the models
discussed, and access to a public domain modeling software environment
that readily permits construction of recurrent network models, and
includes a built-in utility for cluster analysis and principle
components analysis. Since I will have the models with me in a laptop,
there will be time during and after the workshop to conduct new
experiments as well.
Dan Lloyd - Trinity College
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| W08 |
Ron Rensink & Dan Simons:
Change Detection, Attention, and the Contents of Awareness
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This workshop will examine recent evidence from the study of change
blindness: the surprising finding that people fail to notice large
changes to natural scenes. Such findings are particularly striking in
the face of metacognition about change detection. People feel that they
would detect such changes despite the fact that they rarely do. Such
impressions are founded on the intuitive belief that we represent the
details of our visual world. Yet, recent evidence that people fail to
notice large changes to images of natural scenes across eye movements,
blank screens, movie cuts, and real world occlusion events suggests that
we may not.
We will review the conclusions that can be drawn from change blindness
and from related phenomena. Specifically, we consider what these
phenomena can tell us about the structure and accessibility of our
representations. In so doing, we will also examine recent evidence that
change blindness may simply indicate our lack of awareness of the
representations we do have. In other words, non-conscious, implicit
representations of the details of scenes may at least partially underlie
our experience of a stable, continuous visual world. We will also
discuss how the techniques used to study change detection may help to
determine the role of attention and effort in the formation of both
conscious and non-conscious representations. At the end of the
workshop, we will consider how the mechanisms underlying change
blindness and change detection work together to provide a continuous,
stable impression of our visual world.
The workshop will be segmented roughly as follows:
Hour 1: Intentional detection of change
Hour 2: Incidental detection of change
Hour 3: Representations, inattention, and non-awareness
Ron Rensink - Cambridge Basic Research
Dan Simons - Harvard University
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| W09 |
Jackie Andrade & Gareth Jones:
Anaesthesia as a tool for exploring consciousness
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Imagine having drugs with which, simply by varying the dose, you could
produce alterations in consciousness ranging from mild cognitive impairment
to temporary coma. Such drugs could open up a whole range of exciting
possibilities for consciousness research, and they already exist in the
form of commonly used general anaesthetic agents. This workshop will review
the current literature on cognition during anaesthesia and discuss its
implications for our understanding of consciousness. It will discuss some
of the practical problems with using anaesthetics as a research tool and
suggest some methodological solutions. It will be divided into three
sections, each of which will review the current literature and discuss
avenues for future research:
1. Learning during general anaesthesia
Many studies of learning during general anaesthesia have shown implicit
memory, on recovery, for stimuli presented during surgery. However, many
studies have also failed to show learning. As many studies were
opportunistic, there has been little control over factors such as the type
of anaesthetic, type of surgery, or type of memory stimuli. Can patients
really learn information while unconscious? What would be the clinical
implications if they could? One possibility is that patients only formed
implicit memories of intra-operative stimuli if they were inadequately
anaesthetised.
2. Measuring depth of anaesthesia
Giving someone more anaesthetic makes them more unconscious, but the exact
depth of anaesthesia attained depends also on the opposing effects of
surgical stimulation. Depth of anaesthesia is therefore difficult to
predict and, because many patients are given muscle-relaxants during
surgery, it is also difficult to measure. I will describe some recent
research into EEG measures of depth of anaesthesia that may provide useful
tools for consciousness research and clinical practice.
3. The effects of impaired consciousness on cognition
Perhaps the most promising aspect of anaesthetics as a research tool is
their ability to alter cognitive function in a gradual, dose-dependent
fashion. Studies of volunteers receiving small, sub-clinical doses of
anaesthetic may help reveal the "cognitive correlates" of consciousness.
Contrary to other manipulations of consciousness, such as divided attention
or subliminal presentation of stimuli, anaesthetics seem to affect implicit
memory as much as they do explicit memory. What is it about being conscious
which is so important for learning?
Jackie Andrade - University of Sheffield
Gareth Jones - Cambridge University
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| W10 |
Bernard Baars, Giulio Tononi & John Bickle:
Criteria for consciousness in the brain: Methodological implications of recent developments in cognitive neuroscience
|
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When can scientists infer that some brain activity underlies conscious
experience? This workshop reviews 7 sets of studies that make claims
about consciousness in the brain. Each set appears to support at least
one criterion for consciousness: most use the widely used operational
index of accurate reportability of conscious events; some refer to the
distinctive neuroanatomy, neurochemistry, and neuroelectrical activity
of waking consciousness; some to the cortical properties of conscious
contents when compared to matched unconscious events; to local causal
evocation of conscious events; to correspondences between reported
conscious experiences and brain events in timing, topography, and
connectivity; to plausible relations to other known features of
conscious processes, such as limited capacity and a wide range of
contents; and finally, a few studies aim to establish discriminative
validity, to separate the brain basis of consciousness from related
constructs like selective attention, working memory, executive control
and sensory knowledge. Taken together these studies set a very high
threshold for the identification of brain events underlying
consciousness.
Hour 1. Current operational definitions and waking consciousness
Introduction. An historic PET scan obtained by Paulesu and colleagues
(Paulesu, Frith & Frackowiak, 1993, shown in Baddeley, 1993) shows
regions of high metabolic activity in the left hemisphere speech areas
of a subject engaged in silent mental rehearsal. But it is not obvious
from the PET scan which "hot spots" involve conscious events. This
article helps to exemplify the kinds of questions and answers one can
raise about the brain basis of conscious experience.
Current operational definitions. Accurate reportability of a wide range
of stimuli is widely taken to be the most natural observable index of
conscious sensory experiences. A remarkable study by Cowey & Stoerig
(1995) made use of a commentary response to test whether macaques with
cortical blindness lose the phenomenal visual qualia like color and
motion, which humans report losing with similar brain damage. This
approach may provide an equivalent to the reportability criterion in
humans.
Properties of the conscious waking state. Waking consciousness has a
distinctive anatomical, neuroelectrical, and neurochemical signature,
separate from unconscious or low-conscious states. Consciousness during
REM sleep resembles waking consciousness in many respects. Slow-wave
sleep shares similarities with some comas, high-dose general anesthesia,
and epileptic states of absence.
Much evidence supports the idea that conscious contents such as
perceptual experiences or inner speech, require waking consciousness.
This commonsense idea has been challenged by the finding that people
woken up from slow-wave sleep may report mental activity, though
different from typical REM dream reports (Foulkes, 1996; Cavallero et
al, 1990).
Hour Two: Experiments contrasting conscious and unconscious brain
events.
Studies showing differences between conscious and unconscious contents
in the awake brain.
These studies treat consciousness of a given content as an experimental
variable. For example, binocular rivalry allows similar content to be
presented to two eyes, though only one eye will be conscious. The brain
responses to the conscious and unconscious input can therefore be
compared. As Crick (1996) has written, "Binocular rivalry is a
phenomenon of importance in its own right; but its real importance is
that it may shed light on the baffling problem of visual awareness, a
visual form of consciousness."
Local causal evocation of specific conscious contents. Local stimulation
of isolated retina does not lead to conscious experiences. But local
stimulation of visual cortex does lead to conscious phosphenes, which
have recently been used as a prosthesis for the blind. Very local
stimulation of visual neurons in area MT have also been shown to change
the perception of visual events in the macaque (Newsome, 1993).
Conversely, interference with normal cortical processes also blocks
ordinary conscious visual contents.
Studies showing explicit neuronal correspondence between brain events
and reported experiences. Crick and Koch (1995) have argued that area
V1 does not explicitly represent visually conscious information, because
its neurons do not respond to visual features that are lost from
consciousness when V1 is lesioned. This suggests a more general
criterion. Studies by Logothetis and coworkers illustrate this kind of
evidence.
Hour Three: A set of criteria for brain proposals.
The five kinds of studies cited above can provide criteria to be met by
any adequate theory of the brain basis of consciousness. Two more can be
added.
Studies showing plausible relations to other known features of conscious
processes. Any candidate brain basis for consciousness should be
consistent with other well-established features, like limited
moment-to-moment conscious capacity and a wide range of potential
conscious contents. (Baars, 1988, 1997, 1999; Searle, 1994).
Discriminative validity.The brain basis for consciousness must be
distinct from related constructs like selective attention, working
memory, sensory knowledge and executive control.
Bernard Baars - The Wright Institute
Giulio Tononi - The Neurosciences Institute, San Diego
John Bickle - East Carolina University
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| W11 |
Julian Paul Keenan:
Repetitive Transcranial Magnetic Stimulation:
Implications for Research on Consciousness
|
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Philosophical issues, including topics of consciousness, are now
routinely addressed employing functional neuroimaging. Techniques now
widely available including functional Magnetic Resonance Imaging (fMRI)
and Positron Emission Tomography (PET) are providing fundamental answers
to questions relating to consciousness. However, reliance on these
techniques is problematic as the data provided by such methods reveals
only correlation information, which is further complicated by the
indirect measure of neuronal activity via blood oxygenation and the
reliance on control tasks. Repetitive Transcranial Magnetic Stimulation
(rTMS) provides a non-invasive method for establishing causal and
necessary components within cortical networks. When combined with
traditional functional methods such as fMRI and PET, questions as to the
direct nature of cognition and consciousness can be addressed. The use
of this technique is not limited, and the adaptation of rTMS employing
numerous methodolog ies allows for a flexible and specific test of
cognitive hypotheses.
A description of the cortical process of self-awareness is far from
complete, though networks for cognitive processes that are related
(e.g., Theory of Mind) are beginning to be elucidated. The integration
of rTMS with traditional neuroimaging methods addressing the cortical
correlates of self-awareness provides a background in which researchers
interested in consciousness may develop an understanding of rTMS. This
workshop will therefore provide an introduction into the methodologies
of rTMS within the context of examining higher-order cognitive
processes with a specific emphasis on self-directed awareness.
The topics as follows:
- Introduction to rTMS
- Basic Principles of Magnetic Stimulation
- Early Historical Attempts: 19th and 20th Century
- Successful Single-Pulse TMS and the advent of rTMS
- Four Relevant Methodologies
- Virtual Lesions
- Cooling and Heating
- Measures of Cortical Excitability
- Paired Pulse Measures of Inhibition and Excitation
- Integration of Functional Techniques
- What Can Go Wrong
- Direct Measures of Activity within the fMRI and PET environment
- Stereotaxic Methods
- Applications of rTMS in Higher-Order Cognition Not Addressed Previously
- Language & Vision
- Imagery & Memory
- Self & Consciousness
The participants of the workshop should expect to leave the workshop
with an firm and thorough introduction as to the methodologies of rTMS.
Further, the participant will be in a position to implement his or her
own questions of consciousness within the rTMS environment. Therefore
the goals of the workshop are to a) Provide an introduction to those
unfamiliar with rTMS, b) Demonstrate that rTMS can be a powerful tool in
tests of hypotheses related to higher-order consciousness, c) Provide
information and practical information regarding the integration of rTMS
with fMRI and PET, d) Evaluate the shortcomings of the technique, and e)
Provide enough information to the participant so that he or she can
independently evaluate the validity of rTMS for use with his or her own
research. This workshop is intended for persons with an interest in
neuroimaging, and no previous experience with functional techniques is
assumed.
Julian Paul Keenan - Harvard Medical School
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| W12 |
Max Velmans:
Four ways of understanding consciousness: conceptual blocks in dualism, physicalism, functionalism and reflexive monism
|
|
There is not one consciousness/brain problem, but many. These
can be roughly divided into four groups, focused on the following
questions:
- What is consciousness?
- What are the causal relationships
between consciousness and the brain?
- What is the function of
consciousness?
- What are the neural substrates of consciousness?
Some of these questions require empirical advance, some require theoretical
advance, and some require both. If, for example, the problem is "What
are the neural substrates of consciousness?" or, "What forms of
information processing are most closely associated with consciousness?"
then conventional cognitive and neuropsychological techniques are likely
to yield results. But questions about the fundamental nature, causal
efficacy, and function of consciousness have proved to be notoriously
difficult. There are paradoxes that need to be resolved. At first
glance, it seems obvious that consciousness has causal efficacy. There
is extensive evidence that brain states have causal influences on
conscious experiences, and there is extensive evidence that experiences
can have causal influences on the body and brain (earlier experiences
and thoughts, for example, influence later actions). However, neural
material and the "stuff" of conscious experience seem to be very
different, so it is not easy to envisage how these might have causal
influences on each other. One might ask, "How could something subjective
have causal interactions with something objective"?
Similarly, it seems obvious that consciousness has a function. Indeed,
according to evolutionary theory consciousness must have a function
otherwise it would not have evolved to be so central in our lives. There
have been many proposals in the scientific literature about what that
function might be. Common suggestions are that consciousness is
necessary to deal with novelty or complexity, to provide feedback, to
enable memory and learning, to enable language and problem solving, to
enable imaginal short and long-term planning in advance of carrying out
acts in the real world, and so on. However these proposals face a
central dilemma: Once one can specify how such functions work in
information processing terms, one no longer seems to need consciousness
to explain the working of the system which embodies that processing. One
can envisage the same processes operating in mechanical or electrical
systems unaccompanied by any subjective conscious experiences. So -
what, if anything, does subjective experience add to effective
functioning? Questions 1 to 4 also interconnect. If one is not clear
about what consciousness is, how can one find its neural substrates in
the brain? Nor can questions about causal efficacy be dissociated from
questions about function. If consciousness has no causal influence on
neuronal activity, it is not easy to see what its function in the
brain's activity could be.
This workshop summarises the strengths and weaknesses of current
attempts to deal with these problems within dualism, physicalism, and
functionalism. Given the overall focus of the conference on information
integration, we will give particular attention to the proposal that
consciousness carries out the functions of a "global workspace"
concerned with information integration and dissemination (a form of
psychofunctionalism). The workshop will also introduce reflexive monism,
an alternative approach to such problems, developed in depth in
Understanding Consciousness(Routledge, 2000).
Max Velmans - University of London
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Complete URL to this document:
http://www.assc.caltech.edu/assc4/prog/workshops.html
Last updated 11 May 2000 by Axel Cleeremans
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