Roy John, Consciousness Researcher - Abstracts

Posted by:

Alfredo Pereira Jr (group admin)

Date:

25 August 2007

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Dear All:

I will be posting Abstracts from important consciousness researchers, beginning with Roy John. The source is PubMed.

Best Regards,

Alfredo

1: Int J Psychophysiol. 2006 Dec;62(3):377-83. Epub 2006 Mar 2.

The sometimes pernicious role of theory in science.

John ER.

Brain Research Laboratories, Department of Psychiatry, New York University School
of Medicine, New York, NY, United States. roy.john@med.nyu.edu

The role of theory in science is discussed in the context of understanding brain
function. Historically, theories of brain functions have oscillated between
localization and anti-localization beliefs. In the last 50 years, the important
discoveries of the ascending reticular activating system (ARAS), feature
extracting neurons and synaptic growth led many to orthodoxy. Research became
more and more focused upon the elements comprising the nervous system and their
interconnections. The mainstream belief became that many brain functions
including consciousness were localized, certain kinds of brain injuries produced
irreversible functional deficits. Contrary scientific challenges were discouraged
by the omnipresence of such theory. Examples of theoretical “Einstellungen” in
the areas of ARAS, coma, treatment of brain injuries and consciousness are given,
as well as signs that the pendulum is swinging back to an approach to the system
as a whole rather than a focus on its parts.

PMID: 16513198 [PubMed – indexed for MEDLINE]

2: Prog Brain Res. 2005;150:143-71.

From synchronous neuronal discharges to subjective awareness?

John ER.

Brain Research Laboratories, NYU School of Medicine, NY 10016, USA.
johnr01@popmail.med.nyu.edu

For practical clinical purposes, as well as because of their deep philosophical
implications, it becomes increasingly important to be aware of contemporary
studies of the brain mechanisms that generate subjective experiences. Current
research has progressed to the point where plausible theoretical proposals can be
made about the neurophysiological and neurochemical processes which mediate
perception and sustain subjective awareness. An adequate theory of consciousness
must describe how information about the environment is encoded by the exogenous
system, how memories are stored in the endogenous system and released
appropriately for the present circumstances, how the exogenous and endogenous
systems interact to produce perception, and explain how consciousness arises from
that interaction. Evidence assembled from a variety of neuroscience areas,
together with the invariant reversible electrophysiological changes observed with
loss and return of consciousness in anesthesia as well as distinctive
quantitative electroencephalographic profiles of various psychiatric disorders,
provides an empirical foundation for this theory of consciousness. This evidence
suggests the need for a paradigm shift to explain how the brain accomplishes the
transformation from synchronous and distributed neuronal discharges to seamless
global subjective awareness. This chapter undertakes to provide a detailed
description and explanation of these complex processes by experimental evidence
marshaled from a wide variety of sources.

PMID: 16186021 [PubMed – indexed for MEDLINE]

3: Brain Res Brain Res Rev. 2002 Jun;39(1):1-28.

The neurophysics of consciousness.

John ER.

Brain Research Laboratories, NYU School of Medicine, 550 First Avenue, New York
10016, USA. roy@br14.med.nyu.edu

Consciousness combines information about attributes of the present multimodal
sensory environment with relevant elements of the past. Information from each
modality is continuously fractionated into distinct features, processed locally
by different brain regions relatively specialized for extracting these disparate
components and globally by interactions among these regions. Information is
represented by levels of synchronization within neuronal populations and of
coherence among multiple brain regions that deviate from random fluctuations.
Significant deviations constitute local and global negative entropy, or
information. Local field potentials reflect the degree of synchronization among
the neurons of the local ensembles. Large-scale integration, or ‘binding’, is
proposed to involve oscillations of local field potentials that play an important
role in facilitating synchronization and coherence, assessed by neuronal
coincidence detectors, and parsed into perceptual frames by
cortico-thalamo-cortical loops. The most probable baseline levels of local
synchrony, coherent interactions among brain regions, and frame durations have
been quantitatively described in large studies of their age-appropriate normative
distributions and are considered as an approximation to a conscious ‘ground
state’. The level of consciousness during anesthesia can be accurately predicted
by the magnitude and direction of reversible multivariate deviations from this
ground state. An invariant set of changes takes place during anesthesia,
independent of the particular anesthetic agent. Evidence from a variety of
neuroscience areas supporting these propositions, together with the invariant
reversible electrophysiological changes observed with loss and return of
consciousness, are used to provide a foundation for this theory of consciousness.
This paper illustrates the increasingly recognized need to consider global as
well as local processes in the search for better explanations of how the brain
accomplishes the transformation from synchronous and distributed neuronal
discharges to seamless global subjective awareness.

PMID: 12086706 [PubMed – indexed for MEDLINE]

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