electromagnetic brain mapping physiology of source signals · the resting and active brain:...

Sylvain Baillet

McConnell Brain Imaging CentreMontreal Neurological InstituteMcGill University

[sylvain.baillet@mcgill.ca]

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