Antti Revonsuo
Can Functional Brain Imaging Discover Consciousness In the Brain? abstract
Bernard J. Baars
How Could Brain Imaging NOT Tell Us About Consciousness?  abstract
Chris Frith
Commentary on Revonsuo’s ‘Can functional brain imaging discover consciousness in the brain?’  abstract
Julian Paul Keenan
A Thing Done Well. A reply to Dr. Antti Revonsuo’s ‘Can Functional Brain Imaging Discover Consciousness in the Brain?’  abstract
Geraint Rees
Can Philosophy Discover Consciousness In the Brain? Commentary on Revonsuo ‘Can functional brain imaging discover consciousness in the brain?’ abstract
J.G. Taylor
Functional Brain Imaging to Search for Consciousness needs Attention abstract
Antti Revonsuo
Discovering the Mechanisms of Consciousness. Reply to Commentaries abstract

REFEREED PAPER

G. Dalla Barba
Beyond the Memory-Trace Paradox and the Fallacy of the Homunculus: A Hypothesis Concerning the Relationship Between Memory, Consciousness and Temporality abstract

BOOK REVIEWS

Tim Bayne
Co-consciousness: Review of Barry Dainton’s Stream of Consciousness full text
Don Cupitt
Robert L. Arrington and Mark Addis, Wittgenstein and Philosophy of Religion
C. Jason Throop
Gary B. Palmer & Debra J. Occhi (ed.), Languages of Sentiment: Cultural Constructions of Emotional Substrates

ABSTRACTS

Antti Revonsuo

Can Functional Brain Imaging Discover Consciousness in the Brain?

Abstract: If we assume that consciousness is a natural biological phenomenon in the brain, should we expect the current brain sensing and imaging methods to somehow ‘discover’ consciousness? The answer depends on the following points: What kind of level of biological organization do we assume consciousness to be? What would count as the discovery of this level? What are the levels of organization from which the currently available research instruments pick signals and acquire data? Single-cell recordings, PET, fMRI, EEG and MEG pick different types of signals from different levels of organization in the brain. However, it seems they do not manage to pick signals that would allow the direct visualization and reconstruction of the higher levels of electrophysiological organization that are crucial for the empirical discovery and theoretical explanation of consciousness. The message of the present paper is twofold: On the one hand, we should be aware of the practical limitations of the currently available methods of cognitive neuroscience and not read too much into the images produced by them. On the other hand, the present limitations could be overcome by more sophisticated methods in the future. Therefore, contrary to what several philosophers have argued, the empirical discovery of consciousness in the brain is not impossible in principle.

Correspondence: Antti Revonsuo, Department of Philosophy, Center for Cognitive Neuroscience, University of Turku, FIN-20014 Turku, Finland.
Email: antti.revonsuo@utu.fi

Bernard J. Baars

How Could Brain Imaging NOT Tell Us About Consciousness?

Abstract: Revonsuo argues that current brain imaging methods do not allow us to ‘discover’ consciousness. While all observational methods in science have limitations, consciousness is such a massive and pervasive phenomenon that we cannot fail to observe its effects at every level of brain organization: molecular, cellular, electrical, anatomical, metabolic, and even the ‘higher levels of electrophysiological organization that are crucial for the empirical discovery and theoretical explanation of consciousness’ (Revonsuo, this issue).
Indeed, the first major discovery in that respect was Hans Berger’s finding that scalp EEG is massively different between waking and deep sleep, already seven decades ago. We now have perhaps a dozen sophisticated methods for monitoring consciousness-related activity at multiple levels of brain observation. Theoretical progress has come quite rapidly. Recently, E.R. John and colleagues have made fundamental findings using Quantitative EEG, showing consistent brainwide changes as a result of several types of general anaesthetics (John et al., in press). John (in press) has proposed a neuronal ‘field theory’ to account for those results. Another promising new method involves frequency-tagging of competing stimuli, allowing us to follow the activity of billions of neurons synchronized to particular conscious stimuli, always compared to very similar unconscious input (e.g. Tononi et al., 1998; Srinivasan et al., 1999). A fundamental theoretical account of such results has been provided by Tononi & Edelman (1998). Such results and theory are in broad agreement with the cognitive theory proposed by Baars (1983; 1988; 1997; 1998).
 

Correspondence: Bernard J. Baars, The Neurosciences Institute, San Diego, Calif. 92121
Email: Baars@nsi.edu

Chris Frith

Commentary on Revonsuo’s ‘Can functional brain imaging discover consciousness in the brain?’

Antti Revonsuo has given us an engaging and deliberately provocative paper discussing the value of brain imaging in the search for the neural basis of consciousness. In some places, however, his enthusiasm for the controversial nature of the topic has led him to overstate or misdirect his case.

Correspondence: Professor C.D. Frith, Wellcome Dept. of Cognitive Neurology, Institute of Neurology, Queen Square, London, WC1N 3BG, UK.

Julian Paul Keenan

A Thing Done Well. A reply to Dr. Antti Revonsuo’s ‘Can Functional Brain Imaging Discover Consciousness in the Brain?’

Dr. Antti Revonsuo is to be congratulated on his excellent review of the issues surrounding the investigations of the neural correlates of consciousness. In a succinct and concise analysis, he has elucidated numerous trepidations that surround consciousness research. I wish to add only a few brief points.

Correspondence: Julian Paul Keenan, PhD, 224 7th Street, Jersey City, NJ 07302, USA.
Email: jkeenan@caregroup.harvard.edu

Geraint Rees

Can Philosophy Discover Consciousness In the Brain? Commentary on Revonsuo ‘Can functional brain imaging discover consciousness in the brain?’

Revonsuo makes a provocative and interesting claim: that currently available neurophysiological recording techniques will be unable to discover the neural basis of consciousness in the brain. Although the title refers exclusively to functional brain imaging, Revonsuo considers MEG, EEG, ERP and measurements of firing rate in single cell electrophysiology all in principle incapable of discovering consciousness in the brain.

Correspondence: Geraint Rees, Institute of Cognitive Neuroscience, University College London, Alexandra House, 17 Queen Square, London WC1N 3AR
Email g.rees@fil.ion.ucl.ac.uk

J.G. Taylor

Functional Brain Imaging to Search for Consciousness needs Attention

Can the recently developed methods of brain imaging (PET, fMRI, EEG & MEG) help us to discover the neural constituents of consciousness in the brain? This important question actually involves two related questions that need to be answered in order of priority. First of all we need to ask where is consciousness creation sited in the brain? This question is relevant to several recent publications claiming that experimental imaging data place consciousness at least in the regions experimentally observed as activated in the brain during conscious processing, as well as to papers purporting to demonstrate, from a range of neuroscientific data, that consciousness is actually created in one or another specific brain area. The second question comes afterwards: what is the functionality of the neural networks involved in this highly subtle and creative process: how on earth do these regions do it? Some might claim that we do not even need an answer to the first question; it is the second question which poses such a daunting task that it might even be considered impossible to answer. But in any case that second question should be tackled first so as to know what we should be looking for. Yet the thrust of brain imaging — of being able to ‘look inside the brain while it is working’ — seems to provide such a remarkable opportunity to us that we should exploit it to allow us to focus on the place of the creation of consciousness so as to be able to get clues as to how it is achieved. That seems to be the pragmatic scenario being followed by many involved in attempting to probe consciousness by brain imaging (Taylor & Mueller-Gaertner, 1997).

Correspondence: J.G. Taylor, Department of Mathematics, King’s College, Strand, London WC2R2LS, UK.
Email: john.g.taylor@kcl.ac.uk

Antti Revonsuo

Discovering the Mechanisms of Consciousness. Reply to Commentaries

The empirical exploration of the neural mechanisms of consciousness is undoubtedly going to be one of the most central lines of research in the scientific study of consciousness. Therefore, it is important for the researchers involved in these studies to have a clear idea of the phenomenon they are searching for and of the capabilities of the methods they are using to accomplish the task. The main point of my paper ‘Can functional brain imaging discover consciousness in the brain?’ was to explicate and clarify these issues that, although central metatheoretical problems for cognitive neuroscience, have not received much attention from either the experimental neuroscientists or the philosophers involved in the study of consciousness.

Correspondence: Antti Revonsuo, Department of Philosophy, Center for Cognitive Neuroscience, University of Turku, FIN-20014 Turku, Finland.
Email: antti.revonsuo@utu.fi

Gianfranco Dalla Barba

Beyond the Memory-Trace Paradox and the Fallacy of the Homunculus

A Hypothesis Concerning the Relationship Between Memory, Consciousness and Temporality

Abstract: Most theories and models of memory are based on two assumptions that contain theoretical problems. These problems are reflected in the memory-trace paradox, which consists in believing that the past is contained in the memory trace, and in the fallacy of the homunculus, which consists in assuming the existence of an unconscious intentional subject. We will discuss these and present an alternative hypothesis concerning the relationship between memory, consciousness and temporality. This holds that consciousness is not a unitary dimension, but is the set of distinct and original modes to address the object. Among the modes of consciousness, a distinction is made between Knowing Consciousness (KC) and Temporal Consciousness (TC). KC describes the mode of addressing the object in order to know it. TC describes the mode of consciousness that temporalizes its object according the subordinate structures of temporality, the past, the present and the future. Finally it is shown how the hypothesis accounts for a variety of memory disorders and phenomena while avoiding the memory-trace paradox and the fallacy of the homunculus.
 

Correspondence: Gianfranco Dalla Barba, U.324 INSERM, Centre Paul Broca, 2ter rue d’Alésia, 75014 Paris France.
Email: dallabarba@broca.inserm.fr


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