Lachaux J. P., Lutz A., Rudrauf D., Cosmelli D., Le Van Quyen M., Martinerie J. & Varela F. J. (2002) Estimating the time-course of coherence between single-trial brain signals: an introduction to wavelet coherence. Neurophysiologie Clinique 32(3): 157–174.
Lachaux J. P., Lutz A., Rudrauf D., Cosmelli D., Le Van Quyen M., Martinerie J. & Varela F. J.
(
2002)
Estimating the time-course of coherence between single-trial brain signals: an introduction to wavelet coherence.
Neurophysiologie Clinique 32(3): 157–174.
This paper introduces the use of wavelet analysis to follow the temporal variations in the coupling between oscillatory neural signals. Coherence, based on Fourier analysis, has been commonly used as a first approximation to track such coupling under the assumption that neural signals are stationary. Yet, stationary neural processing may be the exception rather than the rule. In this context, the recent application to physical systems of a wavelet-based coherence, which does not depend on the stationarity of the signals, is highly relevant. This paper fully develops the method of wavelet coherence and its statistical properties so that it can be practically applied to continuous neural signals. In realistic simulations, we show that, in contrast to Fourier coherence, wavelet coherence can detect short, significant episodes of coherence between non-stationary neural signals. This method can be directly applied for an ‘online’ quantification of the instantaneous coherence between two signals.
Rudrauf D. & Damasio A. (2006) The biological basis of subjectivity: A hypothesis. In: Kriegel U. & Williford K. (eds.) Self-representational approaches to consciousness. MIT Press, Cambridge MA: 423–465.
Rudrauf D. & Damasio A.
(
2006)
The biological basis of subjectivity: A hypothesis.
In: Kriegel U. & Williford K. (eds.) Self-representational approaches to consciousness. MIT Press, Cambridge MA: 423–465.
Excerpt: Our main hypothesis is that feeling arises in the conflictive dynamics of resistance that our brain and body proper produce when they confront the highly inertial variance that they continuously and inevitably undergo. This variance is the result of delayed auto-perturbations of the brain–body system, divergent motivational tendencies, and attentional shifts. It is not only related to random fluctuations of the system, but also to controlled functional processes, capable of affecting the system as a whole through its functional connectivity. We see the process of resistance to variance, and in particular its central attention-related profile, as delineating the dynamic locus of an internal state of tension through which subjective experience emerges. Such a dynamical structure is intrinsically related to the system’s need to engage in intentional behaviors, attend, preserve coherence, and respect the hierarchy of the various influences that affect its internal dynamics and organization. We see this general dynamics and its subjective counterpart in the framework of a monitoring and control function that lies at the core of the functionality we call consciousness.
Rudrauf D., Lutz A., Cosmelli D., Lachaux J. P. & Le Van Quyen M. (2003) From autopoiesis to neurophenomenology: Francisco varela’s exploration of the biophysics of being. Biological Research 36: 27–65. Fulltext at https://cepa.info/1140
Rudrauf D., Lutz A., Cosmelli D., Lachaux J. P. & Le Van Quyen M.
(
2003)
From autopoiesis to neurophenomenology: Francisco varela’s exploration of the biophysics of being.
Biological Research 36: 27–65.
Fulltext at https://cepa.info/1140
Francisco Varela’s original approach to this “hard problem” presents a subjectivity that is radically intertwined with its biological and physical roots. It must be understood within the framework of his theory of a concrete, embodied dynamics, grounded in his general theory of autonomous systems. Through concepts and paradigms such as biological autonomy, embodiment and neurophenomenology, the article explores the multiple levels of circular causality assumed by Varela to play a fundamental role in the emergence of human experience. The concept of biological autonomy provides the necessary and sufficient conditions for characterizing biological life and identity as an emergent and circular self-producing process. Embodiment provides a systemic and dynamical framework for understanding how a cognitive entity – a mind – can arise in an organism in the midst of its operational cycles of internal regulation and ongoing sensorimotor coupling. Global subjective properties can emerge at different levels from the interactions of components and can reciprocally constrain local processes through an ongoing, recursive morphodynamics. Neurophenomenology is a supplementary step in the study of consciousness. Through a rigorous method, it advocates the careful examination of experience with first-person methodologies. It attempts to create heuristic mutual constraints between biophysical data and data produced by accounts of subjective experience. The aim is to explicitly ground the active and disciplined insight the subject has about his/her experience in a biophysical emergent process. Finally, we discuss Varela’s essential contribution to our understanding of the generation of consciousness in the framework of what we call his “biophysics of being.” Relevance: This paper reviews in detail Francisco Varela’s work on subjectivity and consciousness in the biological sciences.
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