Brain Rhythms, Anatomy, and the Emergence of Consciousness: Why Hearts Don

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Brain Rhythms, Anatomy, and the Emergence of
Consciousness Why Hearts Dont Love and Brains
Dont PumpMemphis Workshop. Consciousness,
Brain Rhythms, and the Action-Perception Cycle,
May 3-4, 2008

• Paul L Nunez PhDEmeritus Professor, Tulane
  University, New Orleans, LA

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Pearls of Wisdom 2008

• Your enemy is your best teacher
• (old Buddhist saying)
• Capitalism is the astounding belief that the most
  wickedest men will do the most wickedest things
  for the greatest good of everyone
• (John Maynard Keynes)

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References

• PL Nunez, Oxford U Press, 2009
• ?Mind, Brain, and the Emergence of Consciousness
• ?Science, Religion, and the Mysteries of
  Consciousness
• PL Nunez and R Srinivasan, Electric Fields of the
  Brain The Neurophysics of EEG, Oxford U Press,
  2006
• www.electricfieldsofthebrain.com
• PL Nunez, Neocortical Dynamics and Human EEG
  Rhythms, Oxford U Press, 1995

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The Holy Grail of brain science connecting
psychology to physiology
EEG, MEG, fMRI, PET,
Thinking and behavior
Dynamic theory (Nonlinear mathematics)
Large scale synaptic action fields
Embedded cell assemblies (neural networks)
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The dynamics of complex systems

• Global weather (suns energy, earths rotation,
  frictional forces, oceans, etc)
• Roulette wheel (initial velocities of ball and
  wheel, frictional forces, hole geometry, etc)
• What anatomical and physiological features of
  brains determine their dynamic (EEG) behaviors?
• Features that underlie observed dynamics may also
  be required for consciousness

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Summary of Todays Talk

• Experimental windows on the mind. What do the
  data tell us?
• Large scale models. What are the essential
  properties of anatomy and physiology?
• Consciousness will not be explained today
• Correlation need not imply causality

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What are the sources of the information presented
today?

• Neurophysiology
• Neuroanatomy
• EEG (recorded from scalp)
• Electrophysiology (intracranial data)
• Complex physical systems
• Mathematical models
• Hunches

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San Diego 1976 16 channel EEG and PDP12 computer
Irvine 2006 131 channel EEG and modern computer
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Human EEG
Spontaneous
Evoked
Depth
ECoG
Transient
Steady State
Scalp
Cognitive Science sensory pathways, stimulus
encoding, motor process, spatial task, verbal
task, mathematics, short term memory, memory
encoding, selective attention, task context,
general intelligence, dynamic brain theory
Clinical Applications epilepsy, head trauma, drug
overdose, brain infection, sleep disorder, coma,
stroke, Alzheimers disease, brain tumor,
multiple sclerosis, surgical monitoring
PL Nunez, EEG,
Encyclopedia of the Brain, 2003
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Selective Sensitivity of EEG and MEG
PL Nunez, Neocortical Dynamics and Human EEG
Rhythms, Oxford U Press, 1995
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Potentials Generated by Synaptic Action in
Cortical Columns
V(r, t)
P(r, t)
r
s(r, w, t)
Potential N columns
V P N (synchronous, parallel)
V P N ½ (random)
1 cm2 cortex 105 minicolumns
Random contribution equals synchronous
contribution for 0.3 synchronous columns
w
PL Nunez R Srinivasan, Electric Fields of the
Brain The Neurophysics of EEG, 2nd Ed, Oxford U
Press, 2006
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fMRI, PET Good spatial resolution and poor
temporal resolution. Tip of the iceberg
measures, 3 above background.
Great red spot on the brain.
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Correlative
Correlative
EEG, MEG
Behavior/Cognition
MRI, PET
Causal
Causal
Speculative

Cell Groups 1
Cell Groups 2
Cell Assemblies
Causal
Speculative
Causal
Synaptic Action Action Potential
Fields ?e(r, t),
?i(r, t), T(r, t)
PL Nunez, Behavioral
and Brain Sciences, 2000
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Cell assemblies at multiple scales, forming
nested hierarchies
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EEG Coherence

• A correlation coefficient expressed as a function
  of frequency
• Measures the phase consistency between two
  signals U(t) and V(t) one measure of phase
  synchronization
• Mostly independent of amplitude
• Depends on spatial scale (like all physical
  measures)

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Robust Coherence Changes Occur with Changes in
Brain State

• Various kinds of mental activity are associated
  with increased coherence between some electrode
  pairs in some frequency bands
• At the same time coherence of other electrode
  pairs and other bands may decrease
• Evidence for the formation and dismantling of
  neural networks on 100 ms time scales?

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8 Hz
Electrode pairs with 100 consistent coherence
increases (left) or reductions (right) during
(1-min) periods of mental calculations.
Comparison with resting periods 11 brain state
transitions. PL Nunez, BM Wingeier RB
Silberstein, Human Brain Mapping, 2001
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5 Hz
Electrode pairs with 100 consistent coherence
increases (left) or reductions (right) during
(1-min) periods of mental calculations.
Comparison with resting periods 11 state
transitions. PL Nunez, BM Wingeier RB
Silberstein, Human Brain Mapping, 2001
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High Resolution EEG

• Given perfect knowledge of scalp potential,
  solution for dura potential is unique
• Accuracy is limited by spatial sampling, head
  model and noise
• The surface Laplacian provides a relatively
  robust estimate of dura potential independent of
• head model

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Simulation of scalp potential (3600 cortical
dipole sources). Laplacian and dura image using
131 scalp samples PL Nunez, BM Wingeier RB
Silberstein, Human Brain Mapping, 2001
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Simulated Scalp Maps
Potential
Laplacian
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Simulated Scalp Cortical Mapdemonstrating
fractal-like neocortical dynamics
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Selective Sensitivity of Potential and Laplacian
Measures to Distinct Spatial Scales of Cortical
Source Activity
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Potential and Laplacian sensitivities to dipole
layers of different sizes
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Alpha rhythm recorded with 111 channels
Potential plots reveal global source field
consistent with anterior--posterior standing wave
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Alpha rhythm recorded with 111 channels
Laplacian plots reveal local source patches in
central and occipital cortex, consistent with
local networks embedded in global field
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Some properties of brain tissue to consider in
relation to consciousness

• Hierarchical interactions across spatial scales
  analogy with social systems
• Non-local interactions by cortico-cortical fibers
• Resonant interactions between networks and
  between networks and global fields

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Some observations on neocortical
anatomy/physiology and consciousness

• Neocortex is interconnected by both intracortical
  (local) and about 1010 corticocortical
  (non-local) fibers
• Any pair of cortical neurons is separated by no
  more than 2 or 3 synapses
• Transit times across the entire brain are of the
  order of 30 ms
• Consciousness requires about 500 ms to develop
  implying multiple positive feedback loops between
  widespread brain regions is required for
  consciousness to occur

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Hierarchical Dynamics of Human Interactions
Neocortex Macrocolumn Module Minicolumn Neuron
??? Global population Nation City Neighborhood Ind
ividual
Biochemistry Quantum Fields ???
Equality of time scales? Top-down, multi-scale
neocortical dynamic plasticity?
PL Nunez, Behavioral and Brain Sciences, 2000
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What Makes the Human Brain Human?

• Cerebral cortex is critical to consciousness, but
  human cortex looks much like cat, rat or cow
  cortex
• Brain size Issues Why are there no elephants,
  whales and dolphins at this workshop ?
• Explanations based on ratio of brain to body
  weight are not useful

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Human Cortico-cortical Fibers(Non-local
Interactions)
100 fibers dissected fibers by Krieg. Actual
number is about 1010, or 100 million for every
one shown see PL Nunez, Neocortical Dynamics and
Human EEG Rhythms, Oxford U Press, 1995)
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Local versus non-local interactions
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Mathematical Models of Real Systems
Model World 1
Model World 2
Real World
Model World N
Black Swans
The Black Swan, Nassim Taleb, 2007. Rare events
with large impacts.
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A linear brain wave equation in 2 dependent
variables Standing waves in the brain.
Synaptic action field
Action potential field
Velocity integral Cortico-cortical
fibers (nonlocal)
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Standing and traveling brain waves
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Dominance of Tangential Over Radial Connections
in the Human Brain
1 mm diameter cortical macrocolumn
100,000 cortico-cortical fibers
2,000 thalamocortical fibers
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Ratio of cortico-cortical input fibers to
thalamocortical input fibers
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A Proposed Marriage of Hebbian Neurophysiology to
Gestalt Psychology

• Cell assemblies (neural networks) embedded in
  global synaptic action fields
• MetaphorSocial networks embedded in a culture
• Top down and bottom up interactions between
  networks and global fields (circular causality)
  

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Resonant Interactions Between Semi-autonomous
Oscillators

• Weakly connected oscillators substantially
  interact only when certain resonant relations
  exist between the characteristic frequencies of
  the autonomous oscillators (a mathematical
  statement largely independent of neural
  oscillator models)
• Eugene Izhikevich, SIAM J App Math, 1999

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Resonant Interactions Between Oscillators 1
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Resonant Interactions Between Oscillators 2
Global Synaptic Field ?(x, t)
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Summary The following physical properties may
be critical for consciousness to occur

• Nested hierarchical interactions across spatial
  scales. Minicolumns within cortico-cortical
  columns within macrocolumns within lobes, etc.
• Non-local interactions by cortico-cortical
  fibers, allowing for much more complex dynamics.
• Resonant interactions between networks and
  between networks and global fields or binding by
  resonance analogous to chemical bonds.
• This raises the speculation that consciousness
  depends critically on resonance phenomena and
  only properly tuned brains can orchestrate the
  beautiful music of sentience.

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Does the brain create the mind?

• Prop 1. Brain creates mind, prob. x
• Prop 2. Brain is antenna, prob. 1 x
• My view
• Brain scientists might consider making a
  distinction between how they proceed as
  scientists (x 100) and what they believe based
  on our measly knowledge (x 50)

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END OF SEMINAR
Begin next 100 years of brain research !