Default mode speaker Stuart Hameroff MD Professor, Anesthesiology and Psychology Director, Center...

Default mode speaker

Stuart Hameroff MDProfessor, Anesthesiology and PsychologyDirector, Center for Consciousness StudiesThe University of Arizona, Tucson Arizona

www.quantumconsciousness.org

“Whilst part of what we perceive comes though our senses from the object before us, another part (and it may be the larger part) always comes out of own head.”

William James, 1890

Consciousness

Lighting

Irony

ScriptStory

Costumes

Actors

Props

Cartesian Theater

Stage

For Des For Descartes, content of consciousness li like a like a play on stage

The ‘Cartesian Theater’

Logic

TopDown

Inputs

Memory

Data

Global Workspace(computers)

GlobalWorkspace

Consciousness

Simon and Newell developed similar brain/mind computer architectures

CPU

Consciousness

ExecutiveCortex

Sensory Inputs

Emotions

Memory

Thalamo-corticalProjections

Cortex

Thalamus

Baars, Edelman/Tononi, Changeux/ Dehaene, Crick/Koch cast thalamo-cortical oscillations, recurrence, global workspace broadcasting……

Based on hierarchical sensory stimuli, arousal, response - bottom-up, top-down,feed-forward, feedback..

PET, fMRI show reduced metabolism, blood flow in thalamo-cortical hierarchical arousal pathways with anesthesia and loss of consciousness – a ‘thalamo-cortical switch’ (Alkire)

In neuroscience, consciousness has been viewed in the context of sensory processing and response, i.e. attention-based tasks

But what about mental states without sensory inputs?

What about task-free, stimulus-independent thought, internally-generated states, mind wandering, episodic memory, meditation, daydreaming?

The Brain's Dark Energy/Default mode networks Raichle (2006) Science 314: 1249 – 1250, 2006)

Copyright restrictions may apply.

Carhart-Harris, R. L. et al. Brain 2010 133:1265-1283; doi:10.1093/brain/awq010

DMN regions in orangeMTL: Medial temporal lobemPFC: Medial prefrontal cortex PCC: Posterior cingulate cortexpIPL: Posterior inferior parietal

Raichle M E et al. PNAS 2001;98:676-682

©2001 by The National Academy of Sciences

Brain regions regularly observed to decrease activity during attention demanding cognitive tasks

Axial (A) and coronal (B) images showing default-mode network for healthy young subjects. Green arrows highlight coactivation in hippocampus and entorhinal cortex.

Axial (A) and coronal (B) images showing default-mode network for healthy young subjects. Green arrows highlight coactivation in hippocampus and entorhinal cortex.

Default-mode networks:healthy elderly

Default modenetworks:Alzheimers

Default mode network activity is one type of intrinsic neuronal activity which was considered noise, until brain-wide correlations in the ‘noise’ were discovered (? Israel)

DMN activities require 95% of the energy required for thalamo-cortical sensory processes

what about internally-generated mental states without sensory inputs?Stimulus-independent thought, e.g. meditation, daydreaming, mind wandering?

The brain operates in two distinct modes –

1) Attention-based sensory processing, task performance (Thalamo-cortical)

2) Mindwandering, episodic memory, internally-generated states daydreaming, thinking…? (Default mode networks)

Default mode networks:

Episodic memory Thinking about consciousness Introspection Meditation Self-referential thought Creativity Daydreaming Jamesian fringe Mind wandering Freudian Id Envisioning the future Anesthesia Gauging others’ perspective SleepContext/filling in

Default mode networks:

Diminished in Alzheimers, autism?

Overactive in schizophrenia, anxiety, OCD?

The brain operates in two distinct modes –

1) Attention-based sensory processing, task performance (Thalamo-cortical)

2) Mindwandering, episodic memory, internally-generated states daydreaming, thinking…? (Default mode networks)

The brain operates in two distinct modes –

1) Attention-based sensory processing, task performance (Thalamo-cortical)

2) Mindwandering, episodic memory, internally-generated states daydreaming, thinking…? (Default mode networks)

and flips back and forth between the two on the order of roughly 10 seconds ‘Anticorrelated networks’ (Raichle)

The Global Signal and Observed Anticorrelated Resting State Brain NetworksMD Fox, D Zhang, AZ Snyder and ME RaichleJ Neurophysiol 101: 3270-3283, 2009

Questions:

1) How does switching between sensory/attention/task and mindwandering/default modes occur?

Locus coeruleus ? (UCSB group)based on saliency of sensory input?

what about internally-generated mental states without sensory inputs?Stimulus-independent thought, e.g. meditation, daydreaming, mind wandering?

Questions:

2) What is/are the function(s) of default mode network activity?

Raichle: Synchrony and orchestration

what about internally-generated mental states without sensory inputs?Stimulus-independent thought, e.g. meditation, daydreaming, mind wandering?

“Default mode networks synchronize all parts of the brain, so like racers in a track competition, they are all in a proper ‘set mode’ when the starting gun goes off.” Raichle 2010

“Orchestrator of The Self : The DMN is thought to behave something like an orchestra conductor, issuing timing signals, much as a conductor waves a baton, to coordinate activity among different brain regions. This cuing—among the visual and auditory parts of the cortex, for instance—probably ensures thatall regions of the brain are ready to react in concert to stimuli.” Raichle, 2010

Steve Lehar

Questions:

3) What about consciousness? What does default mode network activity tell us about consciousness?

Thalamo-cortical sensory processing and behavior can be either conscious, or non-conscious

Default mode network activity can either be conscious, or non-conscious

what about internally-generated mental states without sensory inputs?Stimulus-independent thought, e.g. meditation, daydreaming, mind wandering?

Thalamo-cortical processing (driving to work) can be either conscious or non-conscious (‘auto-pilot’, zombie mode) with daydreaming, mindwandering

what about internally-generated mental states without sensory inputs?Stimulus-independent thought, e.g. meditation, daydreaming, mind wandering?

Default mode network activity can either be conscious (daydreaming about vacation on the beach)….

what about internally-generated mental states without sensory inputs?Stimulus-independent thought, e.g. meditation, daydreaming, mind wandering?

Default mode network activity can either be conscious (daydreaming about vacation on the beach) or non-conscious (tough day ahead at work, send impulses to small bowel, tighten sphincters…..)

what about internally-generated mental states without sensory inputs?Stimulus-independent thought, e.g. meditation, daydreaming, mind wandering?

Activity supporting consciousness switches between

1) Thalamo-cortical input-driven processing and 2) Default mode network activity

what about internally-generated mental states without sensory inputs?Stimulus-independent thought, e.g. meditation, daydreaming, mind wandering?

Consciousness switches between

1) Thalamo-cortical input-driven processing and 2) Default mode network activity

Thalamo-cortical activity is hierarchical, but how is default mode network activity mediated? Self-organized?

what about internally-generated mental states without sensory inputs?Stimulus-independent thought, e.g. meditation, daydreaming, mind wandering?

Consciousness switches between

1) Thalamo-cortical input-driven processing and 2) Default mode network activity

Could consciousness involve some self-organizing neuronal process moving between the two modes?

what about internally-generated mental states without sensory inputs?Stimulus-independent thought, e.g. meditation, daydreaming, mind wandering?

Consciousness switches between

1) Thalamo-cortical input-driven processing and 2) Default mode network activity

Could consciousness involve some self-organizing neuronal process moving between the two modes?

What distinguishes conscious from non-conscious brain activity?

what about internally-generated mental states without sensory inputs?Stimulus-independent thought, e.g. meditation, daydreaming, mind wandering?

The best neurophysiological correlate of consciousness (NCC) comes from EEG, voltage fluctuations recorded from scalp or brain surface.

EEG is divided into frequency bands:

Delta (< 4 Hz)Theta (4 to 8 Hz)Alpha (8 to 12 Hz)Beta (13 to 30 Hz) Gamma (> 30 Hz)

Coherence in gamma synchronyamong different brain regions is the best correlate of consciousness

Gap junction-mediated gamma synchrony in olfactory bulb cortex correlates with conscious smell

.

J Neuroscience. 26(8):2269-77, 2006

Neuron46(5):761-72, 2005

BING!!

Neuroscience. 159(4):1257-63, 2009

Brain Research. 1156:46-58, 2007

Conscious feelings of pleasure, sex and reward correlate with gap junction-mediated gamma synchrony in dopaminergic nucleus accumbens

BING!!

EEG measures post-synapticdendritic activity(not axonal firings)

Biological brain neuron

McCulloch-Pitts artificial neuron, Perceptron

Toy neuron

Integrate

Fire

Integrate

Fire

B I N G ! !

BING!! BING!!

B I N G ! !

The “conscious pilot”—dendritic synchrony moves through the brain to mediate consciousness. Journal of Biological Physics, 36:1 January, 2010DOI: 10.1007/s10867-009-9148-x

Conclusions - Raichle work implies

The brain switches between sensory-driven and (self-organizing) internally-driven modes

what about internally-generated mental states without sensory inputs?Stimulus-independent thought, e.g. meditation, daydreaming, mind wandering?

Conclusions - Raichle work implies

Consciousness switches between sensory-driven and (self-organizing) internally-driven modes

what about internally-generated mental states without sensory inputs?Stimulus-independent thought, e.g. meditation, daydreaming, mind wandering?

Conclusions - Raichle work implies

Consciousness switches between sensory-driven and (self-organizing) internally-driven modes

Anesthesia cannot depend solely on athalamo-cortical switch

what about internally-generated mental states without sensory inputs?Stimulus-independent thought, e.g. meditation, daydreaming, mind wandering?