Transcript Aucun titre de diapositive - Cognitive Computing Research

Do brain rhythms underlie
s 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
Major points.
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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.
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.
from Baars, 1983, 1988, 1997, 2002
Izhikevich et al,
Cerebral
Cortex, 2007.
Modeled 10^5
T-C neurons.
Neuronal
groups emerge
spontaneously.
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.
A brain perspective - limited capacity and
widespread broadcasting.
From Baars & Gage, Cognition, Brain &
Consciousness. Elsevier/ AP, 2007.
Based on K. Friston, 1994. (@ Elsevier)
Massive
unconscious
parallelism
Limited
conscious
contents at
any moment
Dehaene et al (2001) experimental design.
Experimental results:
From Dehaene et al, 2001
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.
"Episodic memory" = memory for
conscious episodes
The Hippocampal Complex includes
neighboring regions in the medial
oare
temporal lobe.
Conscious memories are
retrieved using the same
system.
(Nadel & Moscovitch Multiple Trace Theory. Figure
from M. Moscovitch, personal
comm. )
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 egofunctions - like saying "yes, I see
it!").
Unconscious visual input does
not flow as freely, or as
resonantly, to frontoparietal
areas.
Dehaene et al, 2001
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
Dehaene et al:
Predictions of the global neuronal workspace model
subliminal processing
conscious processing
Masking strength
Early visual areas
Higher visual areas
Prefrontal areas
weak masking
conscious
at threshold
subliminal
strong masking
time following stimulus onset (ms)
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
Variable
delay
9
E
M M
E
16 ms
Frontal
Delay
100 ms
83 ms
66 ms
50 ms
33 ms
16 ms
250 ms
conscious
at threshold
subliminal
Fusiform
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
Melloni et al, - conscious processes involve long-distance synchrony
Palva & Palva, TICS 2007 - alpha and gamma in a global neuronal workspace
Palva and Palva --- alpha band resonance in Working Memory
• faadf
Palva & Palva, TINS 2007
Alpha band
• Gamma & theta interact and cooperate
Jung-Beemann - "Aha! Experience" - Alpha and gamma
rhythms in spontaneous problem solving.
Klimesch et al --- Event--related potentials may be attributable to endogenous rhythms.
• Jensen et al, MEG gamma in episodic
encoding & retrieval
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.