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Do brain rhythms underlie conscious and
unconscious cognition?
Bernard J. Baars The Neurosciences Institute, San
Diego Institute for Intelligent Systems,
University of Memphis
This powerpoint is freely available for
educational use, from www. bernardbaars.pbwiki
.com Baars, 1988, fundamental book on Global
Workspace Theory is available at www.
Nsi.edu/users/baars
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Major points.

• Electromagnetic measures provide our best timing
  measures of brain activities today.
• Brain integration involves both convergent wiring
  and oscillatory resonance (for novel regional
  interactions). (W. Singer et al)
• Synchrony and desynchrony may be the best measure
  of network-level functioning. (Klimesch et al)
• Cognitive theories like Franklin's LIDA may be
  translated into brain theories by identifying
  processing "nodes" with brain arrays and
  "activation passing" with brain resonances.
  LIDA's Cognitive Cycle may imply both gamma and
  near-10-Hz rhythms.
• Gamma resonance is well-established to support
  interaction between specialized regions in
  cortex. (Nunez Srinivasan W. Singer etc.)
• Theta rhythm supports episodic (conscious) memory
  encoding and retrieval in MTL-neocortex
  interaction. (Also voluntary prefrontal executive
  functions.)
• Alpha and gamma interact in spontaneous
  problem-solving. (Jung-Beemann)
• Nonlinear analysis of cortical ECoG shows gamma
  resonance desynchronizing regularly near 10 Hz
  (W.J. Freeman et al), perhaps acting as a
  cortical "shutter" for conscious microstates.
  This mechanism may underlie alpha rhythms and
  intermittent global gamma synchrony.
• ERP's show frontoparietal "ignition" with visual
  conscious input, but not for unconscious input.
  Dehaene et al Melloni et al, 2007 Palva
  Palva, 2007.
• ERP's may reflect the activity of underlying
  brain rhythms (Klimesch, Sauseng, et al).
• Brain rhythms may support a "global neuronal
  workspace" associated with conscious sensation,
  conscious (episodic) memory storage, and recall
  of conscious (episodic) memories. (Dehaene et al
  Melloni et al, 2007 Palva Palva, 2007.
• This system may act as a dynamic core (Edelman et
  al), with flexible input sources, and the ability
  to recruit multiple unconscious functions,
  including memory, language, and executive
  systems.

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The guiding question Why is there conscious
limited capacity along with very large
unconscious capacities?
Conscious functions Unconscious functions
serial massively parallel
self-consistent massively diverse
limited capacity (percepts) huge capacity (e.g., memory)
The key is always to compare conscious and
unconscious events. "contrastive
analysis." Otherwise you're not treating
consciousness as an empirical variable. We always
need closely matched unconscious control
conditions.
Izhikevich et al, Cerebral Cortex, 2007. Modeled
105 T-C neurons. Neuronal groups emerge
spontaneously.
from Baars, 1983, 1988, 1997, 2002
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In the Theater of Consciousness - a useful
theoretical metaphor
--- only the bright spot on stage is conscious
(consciousness is very limited in capacity) ---
sensory inputs compete for access to the
conscious bright spot. --- the "stage"
corresponds to Working Memory --- everthing else
is unconscious, including long-term memory,
automatisms (basal g.) language ---
contexts the director, script writer, etc.,
"backstage" are also unconscious.
From Carl Carpenter, A New Model of
Consciousness, Sci Con Rev.2006.
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A brain perspective - limited capacity and
widespread broadcasting.
Massive unconscious parallelism
Limited conscious contents at any moment
From Baars Gage, Cognition, Brain
Consciousness. Elsevier/ AP, 2007. Based on K.
Friston, 1994. (_at_ Elsevier)
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Dehaene et al (2001) experimental design.
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Experimental results
From Dehaene et al, 2001
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Conscious input is also turned into longterm
memory traces --- via hippocampal-neocortical
distribution.
Hippocampal connections to neocortex --- huge
distribution. This allows neocortex to
constantly learn and update itself with novel and
significant conscious information. Conscious
memories are retrieved using the same system.
(Nadel Moscovitch - Multiple Trace Theory.
Figure from M. Moscovitch, personal comm. )
"Episodic memory" memory for conscious
episodes The Hippocampal Complex includes
neighboring regions in the medial temporal lobe.
oare
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Evoked potentials in Dehaene et al 2001.
Conscious words Unconscious
words
time
156-172 ms
244 ms
476 ms
Conscious visual input activation flows freely to
parietal (egocentric maps) and frontal lobes (for
ego-functions - like saying "yes, I see it!").
Unconscious visual input does not flow as freely,
or as resonantly, to frontoparietal areas.
Dehaene et al, 2001
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Evoked potentials in Del Cul, Baillet Dehaene,
2007
Conscious visual input flows freely to parietal
(egocentric maps) and frontal lobes (for
ego-functions - like saying "yes, I see it!") Co
Unconscious visual input does not flow as freely,
or as resonantly, to frontoparietal areas.
Del Cul, Baillet, Deheane, PLOS Biol., 2007
oare
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Dehaene et al Predictions of the global
neuronal workspace model
subliminal processing
conscious processing
Masking strength
weak masking
conscious
at threshold
subliminal
strong masking
time following stimulus onset (ms)
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Source analysis of masking experiment Del Cul,
Baillet Dehaene, PLOS Biology 2007
Parietal
The late non-linearity is associated with -
sudden inferior frontal activation - a second
wave of parieto-temporal activation
Activation at 370 ms
Fusiform
Frontal
Delay
conscious
at threshold
subliminal
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Basirat et al, 2008 - parieto-frontal gamma
resonance in speech perception. Red blue dots
showed intense gamma band activity in
intracranial recordings.
40 Hz
40 Hz
40 Hz
40 Hz
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Melloni et al, - conscious processes involve
long-distance synchrony
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Palva Palva, TICS 2007 - alpha and gamma in a
global neuronal workspace
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Palva and Palva --- alpha band resonance in
Working Memory

• faadf

Palva Palva, TINS 2007
Alpha band
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• Gamma theta interact and cooperate

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Jung-Beemann - "Aha! Experience" - Alpha and
gamma rhythms in spontaneous problem solving.
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Klimesch et al --- Event--related potentials may
be attributable to endogenous rhythms.
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• Jensen et al, MEG - gamma in episodic encoding
  retrieval

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Summary Do brain rhythms underlie conscious and
unconscious cognition?

• Electrophysiological measures provide our best
  timing measures of brain activities today.
• Brain integration involves both convergent wiring
  and oscillatory resonance (for novel regional
  interactions). (W. Singer et al)
• Synchrony and desynchrony may be the best measure
  of network-level functioning. (Klimesch et al)
• Cognitive theories like Franklin's LIDA may be
  translated into brain theories by identifying
  processing "nodes" with brain arrays and
  "activation passing" with brain resonances.
  (especially gamma). LIDA's Cognitive Cycle gives
  a functional description of human cognition.
• Gamma resonance is well-established to support
  interaction between specialized regions in
  cortex. (Nunez Srinivasan)
• Theta rhythm supports episodic (conscious) memory
  encoding and retrieval in MTL-neocortex
  interaction. (Also voluntary prefrontal control
  aspects of memory.)
• Alpha and gamma interact in spontaneous
  problem-solving. (Jung-Beemann)
• Nonlinear analysis of cortical ECoG shows gamma
  resonance desynchronizing regularly near 10 Hz
  (W.J. Freeman et al), perhaps acting as a
  cortical "shutter" for conscious microstates.
  This may underlie alpha rhythms and intermittent
  global gamma synchrony.
• ERP's show frontoparietal "ignition" with visual
  conscious input, but not for unconscious input.
  (Dehaene et al)
• ERP's may reflect the activity of underlying
  brain rhythms (Klimesch, Sauseng, et al).
• Brain rhythms may support a "global neuronal
  workspace" associated with conscious sensation,
  conscious (episodic) memory storage, and recall
  of conscious (episodic) memories.
• This system may act as a dynamic core (Edelman et
  al), with flexible input sources, and the ability
  to recruit multiple unconscious functions,
  including memory, language, and executive
  systems.