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Sylvain Baillet
McConnell Brain Imaging CentreMontreal Neurological InstituteMcGill University
Google it! ’MEG MNI ’
Electromagnetic Brain MappingPhysiology of source signals
Ongoing background brain activity (MEG)
[1.5-40] Hz
Amplitude scale
Ongoing background brain activity (MEG)
Amplitude scale
[40-350] Hz
Withsubject
Withoutsubject
Hamalainen et al., Rev. Mod. Phys., 1993
Power line contamination
The resting and active brain: frequency power spectrum
Withsubject
Withoutsubject
Hamalainen et al., Rev. Mod. Phys., 1993
Power line contamination
The resting and active brain: frequency power spectrum
delta
theta alpha
beta terra
incognita
gamma
The resting and active brain: frequency power spectrum
State-‐dependent expressions of neural oscilla3ons
Large-scale electrophysiology; oscillatory “brain rhythms”
aroused β
relaxed α
drowsy 𝜃
light sleep (spindles)
deep sleep δ
State-‐dependent expressions of neural oscilla3ons
Raichle M. Brain Connectivity (2011)
?
fMRI - BOLD
Large-scale electrophysiology; oscillatory “brain rhythms”
aroused β
relaxed α
drowsy 𝜃
light sleep (spindles)
deep sleep δ
State-‐dependent expressions of neural oscilla3ons
“Resting-state networks”Buckner RL et al. Ann NY Acad. Sci. (2008)Carhart-Harris R L , Friston K J Brain (2010)
Resting-state networks
Raichle M. Brain Connectivity (2011)
?
fMRI - BOLD
Large-scale electrophysiology; oscillatory “brain rhythms”
aroused β
relaxed α
drowsy 𝜃
light sleep (spindles)
deep sleep δ
State-‐dependent expressions of neural oscilla3ons
“Resting-state networks”Buckner RL et al. Ann NY Acad. Sci. (2008)Carhart-Harris R L , Friston K J Brain (2010)
Resting-state networks
Raichle M. Brain Connectivity (2011)
?
fMRI - BOLD
Large-scale electrophysiology; oscillatory “brain rhythms”
aroused β
relaxed α
drowsy 𝜃
light sleep (spindles)
deep sleep δ
Electrophysiological origins of MEG/EEG signals
The neural cell as elementary building block
The neural cell as elementary building block
The neural cell as elementary building block
The neural cell as elementary building block
pyramidal cell as canonical source
Basic neural electrophysiology
apical dentrites
basal dentrites
Basic neural electrophysiology
apical dentrites
basal dentrites
- - - - - - - -- - - - - - - -
Basic neural electrophysiology
apical dentrites
basal dentrites
- - - - - - - -- - - - - - - -
++ + + + + + + + + + + +
Basic neural electrophysiology
apical dentrites
basal dentrites
- - - - - - - -- - - - - - - -
++ + + + + + + + + + + +
primary current
Basic neural electrophysiology
apical dentrites
basal dentrites
- - - - - - - -- - - - - - - -
++ + + + + + + + + + + +
return (volume) currents
primary current
Basic neural electrophysiology
apical dentrites
basal dentrites
- - - - - - - -- - - - - - - -
++ + + + + + + + + + + +
return (volume) currents
primary current
Basic neural electrophysiology
apical dentrites
basal dentrites
- - - - - - - -- - - - - - - -
++ + + + + + + + + + + +
return (volume) currents
primary current
Basic neural electrophysiology
apical dentrites
basal dentrites
- - - - - - - -- - - - - - - -
++ + + + + + + + + + + +
primary current
Basic neural electrophysiology
apical dentrites
basal dentrites
- - - - - - - -- - - - - - - -
++ + + + + + + + + + + +
magnetic induction
primary current
magnetometer
Basic neural electrophysiology
apical dentrites
basal dentrites
- - - - - - - -- - - - - - - -
++ + + + + + + + + + + +
magnetic induction
primary current
magnetometer
Basic neural electrophysiology
apical dentrites
basal dentrites
- - - - - - - -- - - - - - - -
++ + + + + + + + + + + +
magnetic induction
primary current
measured induced currents
= +
The equivalent current dipole =
current source model of PSP’s and AP’s
current dipole model
= +
The equivalent current dipole =
current source model of PSP’s and AP’s
current dipole model
= +
The equivalent current dipole =
current source model of PSP’s and AP’s
current dipole model
influence of cell morphology on signal strength
radial cell morphology
influence of cell morphology on signal strength
radial cell morphology
net current dipole
influence of cell morphology on signal strength
radial cell morphology
net current dipole
weaker net currents than from elongated cell morphology
Mass effect of neural ensembles
Mass effect of neural ensembles
Mass effect of neural ensembles
Mass effect of neural ensembles
Mass effect of neural ensembles
Mass effect of neural ensembles
Mass effect of neural ensembles
Mass effect of neural ensembles
overlap of multiple PSPs yields stronger contribution to MEG/EEG signalling
Mass effect of neural ensembles
overlap of multiple PSPs yields stronger contribution to MEG/EEG signalling
stronger individual currents but poorer temporal overlap of APs
Mass effect of neural ensembles
overlap of multiple PSPs yields stronger contribution to MEG/EEG signalling
stronger individual currents but poorer temporal overlap of APs
Mass effect of neural ensembles
overlap of multiple PSPs yields stronger contribution to MEG/EEG signalling.
~50,000 cells, at minimum
stronger individual currents but poorer temporal overlap of APs
Mass effect of neural ensembles
Mass effect of neural ensembles
Mass effect of neural ensemblesVoltage-‐sensi3ve ion channels (Llinás, 1988; Hille, 2001)
-‐ Large, detectable PSP sodium spikes
‣ from 10,000 synchronous cells
‣ a possible source of high-‐frequency bursts?
Mass effect of neural ensembles
experimental data (micro)MEG
Murakami et al., J. Physiol (2002)
Voltage-‐sensi3ve ion channels (Llinás, 1988; Hille, 2001)
-‐ Large, detectable PSP sodium spikes
‣ from 10,000 synchronous cells
‣ a possible source of high-‐frequency bursts?
mesoscopic distribu3on of currents
cortex
mesoscopic distribu3on of currents
cortex
mesoscopic distribu3on of currents
cortex
nuclei
mesoscopic distribu3on of currents
cortex
nuclei
dynamicsa rapid overview
dynamicsa rapid overview
Evidence of low-‐to-‐high frequency coupling of neural oscilla3ons: single cells & assemblies
Contreras & Steriade, J. Neurosci. (1995)
Temporal ji_er of unitary and ensemble responses
Thalamic stimulation Cortical responseContreras & Steriade, J. Neurophys. (1996)
Ji_er in brain responses or s3mulus 3ming yields slower event-‐related components and lower SNR
• Sloppy s3mulus 3ming (ji_er) yields smeared MEG responses
• Physiological ji_er produces similar effects
• The longer the response latency, the longer and smoother the response
Somatosensory evoked fields
Latency
Adapted from L. Parkkonen
Oscilla3onsa scaffold of neural dynamics
Oscilla3onsa scaffold of neural dynamics
Theore3cal framework: Oscillatory Implementa3on of Perceptual Inference
Donhauser, Florin & Baillet, CNS 2014 Schroeder & Lakatos, TINS 2009 Arnal & Giraud, TICS 2012
Theore3cal framework: Oscillatory Implementa3on of Perceptual Inference
Donhauser, Florin & Baillet, CNS 2014 Schroeder & Lakatos, TINS 2009 Arnal & Giraud, TICS 2012
Slow Inhibitory
Fast InhibitoryExcitatory
Elementary cell assembly
Theore3cal framework: Oscillatory Implementa3on of Perceptual Inference
Donhauser, Florin & Baillet, CNS 2014 Schroeder & Lakatos, TINS 2009 Arnal & Giraud, TICS 2012
Slow Inhibitory
Fast InhibitoryExcitatory
Elementary cell assembly
MEG, EEG, LFP
Theore3cal framework: Oscillatory Implementa3on of Perceptual Inference
Donhauser, Florin & Baillet, CNS 2014 Schroeder & Lakatos, TINS 2009 Arnal & Giraud, TICS 2012
Slow Inhibitory
Fast InhibitoryExcitatory
Elementary cell assembly
E EE
I I
MEG, EEG, LFP
Theore3cal framework: Oscillatory Implementa3on of Perceptual Inference
Donhauser, Florin & Baillet, CNS 2014 Schroeder & Lakatos, TINS 2009 Arnal & Giraud, TICS 2012
Slow Inhibitory
Fast InhibitoryExcitatory
Elementary cell assembly
E EE
I I
MEG, EEG, LFP
δ-α cycles
Theore3cal framework: Oscillatory Implementa3on of Perceptual Inference
Donhauser, Florin & Baillet, CNS 2014 Schroeder & Lakatos, TINS 2009 Arnal & Giraud, TICS 2012
Slow Inhibitory
Fast InhibitoryExcitatory
Elementary cell assembly
E EE
I I
MEG, EEG, LFP
δ-α cycles
𝜸
Theore3cal framework: Oscillatory Implementa3on of Perceptual Inference
Donhauser, Florin & Baillet, CNS 2014 Schroeder & Lakatos, TINS 2009 Arnal & Giraud, TICS 2012
Slow Inhibitory
Fast InhibitoryExcitatory
Elementary cell assembly
E EE
I I
MEG, EEG, LFP
δ-α cycles
𝜸 𝜸
Theore3cal framework: Oscillatory Implementa3on of Perceptual Inference
Donhauser, Florin & Baillet, CNS 2014 Schroeder & Lakatos, TINS 2009 Arnal & Giraud, TICS 2012
Slow Inhibitory
Fast InhibitoryExcitatory
Elementary cell assembly
E EE
I I
MEG, EEG, LFP
δ-α cycles
𝜸 𝜸 𝜸
Theore3cal framework: Oscillatory Implementa3on of Perceptual Inference
Donhauser, Florin & Baillet, CNS 2014 Schroeder & Lakatos, TINS 2009 Arnal & Giraud, TICS 2012
Slow Inhibitory
Fast InhibitoryExcitatory
Elementary cell assembly
E EE
I I
STIM MEG, EEG, LFP
δ-α cycles
𝜸 𝜸 𝜸
E EE
I I δ-α cycles
𝜸 𝜸 𝜸
Theore3cal framework: Oscillatory Implementa3on of Perceptual Inference
Donhauser, Florin & Baillet, CNS 2014 Schroeder & Lakatos, TINS 2009 Arnal & Giraud, TICS 2012
Slow Inhibitory
Fast InhibitoryExcitatory
Elementary cell assembly
STIM MEG, EEG, LFP
E EE
I I δ-α cycles
𝜸 𝜸 𝜸
Theore3cal framework: Oscillatory Implementa3on of Perceptual Inference
Donhauser, Florin & Baillet, CNS 2014 Schroeder & Lakatos, TINS 2009 Arnal & Giraud, TICS 2012
Slow Inhibitory
Fast InhibitoryExcitatory
Elementary cell assembly
SI
FIE
Higher-order region
STIM MEG, EEG, LFP
E EE
I I δ-α cycles
𝜸 𝜸 𝜸
Theore3cal framework: Oscillatory Implementa3on of Perceptual Inference
Donhauser, Florin & Baillet, CNS 2014 Schroeder & Lakatos, TINS 2009 Arnal & Giraud, TICS 2012
Slow Inhibitory
Fast InhibitoryExcitatory
Elementary cell assembly
SI
FIE
Higher-order region
STIM MEG, EEG, LFP
E EE
I I δ-α cycles
𝜸 𝜸 𝜸
Theore3cal framework: Oscillatory Implementa3on of Perceptual Inference
Donhauser, Florin & Baillet, CNS 2014 Schroeder & Lakatos, TINS 2009 Arnal & Giraud, TICS 2012
Slow Inhibitory
Fast InhibitoryExcitatory
Elementary cell assembly
SI
FIE
Higher-order region
Cortical hub, thalamic relaySTIM MEG, E
EG, LFP
E EE
I I δ-α cycles
𝜸 𝜸 𝜸
Theore3cal framework: Oscillatory Implementa3on of Perceptual Inference
Donhauser, Florin & Baillet, CNS 2014 Schroeder & Lakatos, TINS 2009 Arnal & Giraud, TICS 2012
Slow Inhibitory
Fast InhibitoryExcitatory
Elementary cell assembly
SI
FIE
Higher-order region
Cortical hub, thalamic relay
β burstsSTIM MEG, E
EG, LFP
E EE
I I δ-α cycles
𝜸 𝜸 𝜸
Theore3cal framework: Oscillatory Implementa3on of Perceptual Inference
Donhauser, Florin & Baillet, CNS 2014 Schroeder & Lakatos, TINS 2009 Arnal & Giraud, TICS 2012
Slow Inhibitory
Fast InhibitoryExcitatory
Elementary cell assembly
SI
FIE
Higher-order region
Cortical hub, thalamic relay
β burstsSTIM MEG, E
EG, LFP
E EE
I I δ-α cycles
𝜸 𝜸 𝜸
Theore3cal framework: Oscillatory Implementa3on of Perceptual Inference
Donhauser, Florin & Baillet, CNS 2014 Schroeder & Lakatos, TINS 2009 Arnal & Giraud, TICS 2012
Slow Inhibitory
Fast InhibitoryExcitatory
Elementary cell assembly
SI
FIE
Higher-order region
Cortical hub, thalamic relay
β burstsSTIM MEG, E
EG, LFP
E EE
I I δ-α cycles
𝜸 𝜸 𝜸
Theore3cal framework: Oscillatory Implementa3on of Perceptual Inference
Donhauser, Florin & Baillet, CNS 2014 Schroeder & Lakatos, TINS 2009 Arnal & Giraud, TICS 2012
Slow Inhibitory
Fast InhibitoryExcitatory
Elementary cell assembly
SI
FIE
Higher-order region
Cortical hub, thalamic relay
β burstsSTIM MEG, E
EG, LFP
E EE
I I δ-α cycles
𝜸 𝜸 𝜸
Theore3cal framework: Oscillatory Implementa3on of Perceptual Inference
Donhauser, Florin & Baillet, CNS 2014 Schroeder & Lakatos, TINS 2009 Arnal & Giraud, TICS 2012
Slow Inhibitory
Fast InhibitoryExcitatory
Elementary cell assembly
SI
FIE
Higher-order region
Cortical hub, thalamic relay
β burstsSTIM STIM MEG, E
EG, LFP
E EE
I I δ-α cycles
𝜸 𝜸 𝜸
Theore3cal framework: Oscillatory Implementa3on of Perceptual Inference
Donhauser, Florin & Baillet, CNS 2014 Schroeder & Lakatos, TINS 2009 Arnal & Giraud, TICS 2012
Slow Inhibitory
Fast InhibitoryExcitatory
Elementary cell assembly
SI
FIE
Higher-order region
Cortical hub, thalamic relay
β burstsSTIM STIMSTIM MEG, E
EG, LFP
E EE
I I δ-α cycles
𝜸 𝜸 𝜸
Theore3cal framework: Oscillatory Implementa3on of Perceptual Inference
A possible mechanism for op3mal sensory processing (efficacy in 3ming, metabolism, downstream processing, etc.)
Donhauser, Florin & Baillet, CNS 2014 Schroeder & Lakatos, TINS 2009 Arnal & Giraud, TICS 2012
Slow Inhibitory
Fast InhibitoryExcitatory
Elementary cell assembly
SI
FIE
Higher-order region
Cortical hub, thalamic relay
β burstsSTIM STIMSTIM MEG, E
EG, LFP
Wrap-‐up: dis3nct roles for dis3nct frequencies
Wrap-‐up: dis3nct roles for dis3nct frequencies
Wrap-‐up: dis3nct roles for dis3nct frequencies
δ-α: cycles of regional excitability
Wrap-‐up: dis3nct roles for dis3nct frequencies
δ-α: cycles of regional excitability
β: bursts as expressions of top-down modulations
Wrap-‐up: dis3nct roles for dis3nct frequencies
δ-α: cycles of regional excitability
β: bursts as expressions of top-down modulations
𝜸: bursts nested in slower rhythms, bottom-up signaling
Wrap-‐up: dis3nct roles for dis3nct frequencies
δ-α: cycles of regional excitability
β: bursts as expressions of top-down modulations
𝜸: bursts nested in slower rhythms, bottom-up signaling
E EE
I I
Wrap-‐up: dis3nct roles for dis3nct frequencies
δ-α: cycles of regional excitability
β: bursts as expressions of top-down modulations
𝜸: bursts nested in slower rhythms, bottom-up signaling
E EE
I I
higher 𝜸: PSP spiking ?
Correla3on between low-‐, high-‐frequency ongoing brain rhythms and BOLD
Schölvinck et al., PNAS (2010)
Delta/Theta/Alpha
Beta
Gamma
High-Gamma
MEG Res3ng-‐State Networks
Auditory+
VisualDMN
Dorsal, sensori-motor
fMRI
Florin & Baillet, Neuroimage, 2015
delta
theta alpha
beta terra
incognita
gamma
Cross-‐frequency coupling (CFC): A generic mechanism regula3ng local and long-‐range brain dynamics?
delta
theta alpha
beta terra
incognita
gamma
Cross-‐frequency coupling (CFC): A generic mechanism regula3ng local and long-‐range brain dynamics?
delta
theta alpha
beta terra
incognita
gamma
Cross-‐frequency coupling (CFC): A generic mechanism regula3ng local and long-‐range brain dynamics?
E EEI I
Review
Review
• Signal origins
Review
• Signal origins
๏ currents induced by spa3o-‐temporal overlap of post-‐synap3c poten3als in cell assemblies (cortex and elsewhere)
Review
• Signal origins
๏ currents induced by spa3o-‐temporal overlap of post-‐synap3c poten3als in cell assemblies (cortex and elsewhere)
๏ possible fast spiking ac3vity
Review
• Signal origins
๏ currents induced by spa3o-‐temporal overlap of post-‐synap3c poten3als in cell assemblies (cortex and elsewhere)
๏ possible fast spiking ac3vity
• Dynamics
Review
• Signal origins
๏ currents induced by spa3o-‐temporal overlap of post-‐synap3c poten3als in cell assemblies (cortex and elsewhere)
๏ possible fast spiking ac3vity
• Dynamics
๏ event-‐related responses as resejng of ongoing ac3vity
Review
• Signal origins
๏ currents induced by spa3o-‐temporal overlap of post-‐synap3c poten3als in cell assemblies (cortex and elsewhere)
๏ possible fast spiking ac3vity
• Dynamics
๏ event-‐related responses as resejng of ongoing ac3vity
๏ dis3nct roles of typical frequency bands: net excita3on, bo_om-‐up vs top-‐down signaling, etc
Review
• Signal origins
๏ currents induced by spa3o-‐temporal overlap of post-‐synap3c poten3als in cell assemblies (cortex and elsewhere)
๏ possible fast spiking ac3vity
• Dynamics
๏ event-‐related responses as resejng of ongoing ac3vity
๏ dis3nct roles of typical frequency bands: net excita3on, bo_om-‐up vs top-‐down signaling, etc
๏ a field of intense research