Neuroimaging: Intracortical, fMRI, EEG

MACHINE LEARNING ON NEUROIMAGING DATA

Ilya Kuzovkin

AACIMP, August 2014

LECTURE 1: NEUROIMAGING TECHNIQUES

THE COURSE

NEUROIMAGING DATA

THE COURSE

NEUROIMAGING DATA

MACHINE LEARNING

THE COURSE

NEUROIMAGING DATA

MACHINE LEARNING

BRAIN-COMPUTER INTERFACE

P2 P3+ =

PART I INTRACORTICAL

NEURONS

http://biomedicalengineering.yolasite.com

NEURONS

http://faculty.tcc.edu/mmitchell/142/ap-graph1.jpg

How can voltage be negative?

http://newton.umsl.edu/tsytsarev_files/neuron_electrode.JPG

ELECTRODES

THE SIGNAL

• Local Field Potential

http://www.frontiersin.org/files/Articles/414/fnins-02-037/image_m/fnins-02-037-g001.jpg http://lifesciences.ieee.org/images/stories/life-sciences/2012-01-spike-01_l.png

THE SIGNAL • Multi-unit spikes

Spike sorting

THE SIGNAL

• Multi-unit spikes

• Single-unit spikes

Spike sorting

For each measured neuron we record the time moments when it spiked

RASTER PLOT

What is on the X axis?

RASTER PLOT

What is on the Y axis?

RASTER PLOT

rastrum

PSTHPost-Stimulus Time Histogram

Post-Stimulus Time Histogram

What is on the Y axis?

Post-Stimulus Time Histogram

TUNING CURVE

http://www.beatricebiologist.com/2012/11/types-of-cells.html

TUNING CURVE

40 spikes per second (40 Hz)45

TUNING CURVE

40 spikes per second (40 Hz)

TUNING CURVE

What do you expect to see on this plot?0

TUNING CURVE

SUMMARY

• High spatial resolution (up to single neuron)

!• High temporal resolution

SUMMARY

What does “spatial resolution” mean?

SUMMARY

• Requires surgery !• Localized

What does “temporal resolution” mean?

SUMMARY

Very informative and precise, but not applicable to general

audience due to surgery.

PART II FMRI

http://www.csulb.edu/~cwallis/482/fmri/fmri.h3.gif http://neuro.mediasauce.com/images/fmri_machine.png

NUCLEAR MAGNETIC RESONANCE

Physical phenomenon in which nucleus of an atom can absorb or reemit

electromagnetic radiation if placed in a magnetic field

electromagnetic radiation if placed in a magnetic field.

Spin-UP +1/2

Spin-DOWN -1/2

http://www.markusehrenfried.de/science/physics/hermes/whatisspin.html

Spin-UP +1/2

Spin-DOWN -1/2

http://www.markusehrenfried.de/science/physics/hermes/whatisspin.html

Nothing actually spins in there. No analogy in classical mechanics.

Spin-UP +1/2

Spin-DOWN -1/2

Nothing actually spins in there. No analogy in classical mechanics.

But why call it spin then?http://www.markusehrenfried.de/science/physics/hermes/whatisspin.html

http://www.howequipmentworks.com/physics/medical_imaging/mri/magnetic_resonance_imaging.html

NOT A JOKE

Six known types of quarks and their official names. So spin is not that bad.

MAGNETIC MOMENT

Particle with non-zero nuclear spin is like a

small magnet.

MAGNETIC MOMENT

small magnet.

MAGNETIC MOMENT

small magnet.

MAGNETIC MOMENT

small magnet.

IN A MAGNETIC FIELD

What happens to a magnet if you put it in a magnetic field?

IN A MAGNETIC FIELD

What happens to a magnet if you put it in a magnetic field?

IN A MAGNETIC FIELD

Stronger field — larger energy gap

Nuclear Magnetic Resonance

?Nuclear Magnetic Resonance

RADIO FREQUENCY PULSE

We can give energy to a particle

and move it to a higher energy level

To do that we send an electromagnetic wave

Nucleus will absorb energy only if frequency of the wave is correct for

• the nucleus we work with • strength of the magnetic field

To do that we send an electromagnetic wave

RELAXATION

Now we stop the pulse

RELAXATION

Nucleus will give out same amount of energy in the form of electromagnetic radiation.

Nuclear Magnetic Resonance Imaging

HYDROGEN

Possible spin states +1/2 or -1/2

HYDROGEN IN A MAGNETIC FIELD

RF PULSE

What will happen?

RF PULSE

RELAXATION

For different tissues the time of relaxation

is different

NUCLEI SEND SIGNALS

One large piece is still missing…

GRADIENT COILS

http://www.howtolearn.com/HTL/media/Visualisations-in-Medicine-MRI-Hi-Res-Crop1.jpg

GRADIENT COILS

FMRI F FOR FUNCTIONAL*

*MRI signals associated with functional brain activity

BOLDBLOOD-OXYGEN-LEVEL DEPENDENT

Active neuron Passive neuron

I need oxygen and

glucose!I need nothing…

Have different magnetic resonance

Distinguishable by MRI

FMRI DATA

• High spatial resolution !• No surgery! !• Records whole brain

SUMMARY

• Low temporal resolution !• Cost !• Size

Still pretty informative and precise, does not require a surgery, but is huge and costs a lot.

https://www.coursera.org/course/fmri

PART III EEG

http://infantlab.psych.sc.edu/PWREEGDemoBaby

NEURONS

http://www.conncad.com/gallery/single_cells.html

NEURONS

http://en.wikipedia.org/wiki/Neural_oscillation

NEURONS

What is the frequency in this example?

BRAINWAVES

BRAINWAVESDelta 0-4 Hz

Theta 4-7 Hz

Alpha 7-14 Hz

Mu 8-13 Hz

Beta 15-30 Hz

Gamma 30-100 Hz

BRAINWAVESDelta 0-4 Hz

Theta 4-7 Hz

Alpha 7-14 Hz

Mu 8-13 Hz

Beta 15-30 Hz

Gamma 30-100 Hz

slow wave sleep, babies, lesions

children, drowsiness, meditation, relaxed

closed eyes, relaxed

motor neuron in rest, mirror neurons

motor activity, anxious thinking, concentration

networking between populations of neurons

Alpha 7-14 Hz

Beta 15-30 Hz

Gamma 30-100 Hz

Alpha 7-14 Hz

Beta 15-30 Hz

Gamma 30-100 Hz

Jean Baptiste Joseph Fourier 1768 — 1830

FOURIER TRANSFORM*

*discrete

FOURIER TRANSFORM*

*discrete

FOURIER TRANSFORM*

*discrete

signal at time t frequency complex number

FOURIER TRANSFORM*

*discrete

Amplitude of the component with

frequency k

FOURIER TRANSFORM*

*discrete

Amplitude of the component with

frequency k

EEG DATA

TIME-FREQUENCY DOMAIN

Are we done?

EEG DATA

Are we done?

EEG DATA

300 MS

EEG DATA

300 MS

EEG DATA

300 MS

EEG DATA

300 MS

EEG DATA

300 MS

10 channels 50 frequencies 3 seconds of data 300 ms window

EEG DATA

300 MS

• How many numbers to describe 1 reading of 300 ms?

EEG DATA

300 MS

• How many numbers to describe 1 reading of 300 ms?

• How many numbers to describe all 3 seconds of data?

EEG DATA

• High temporal resolution !• No surgery! !• Mobile

!• Cheap

SUMMARY

• Low spatial resolution

Available to wide audience, but measurements are approximate.

SUMMARY OF NEUROIMAGING TECHNIQUESTechnology Electrical Magnetic Optical

Name EEG ECoG Intracortical MEG fMRI fNIRS

Invasive !

Portable !

Cost From $100 to $30,000+ $1000 grid

$2000 per array $1 mln $2-3

mln $200,000

Temporal resolution 50 ms 3 ms 3 ms 50ms 1-2 s 1 s

Spatial resolution 1+ cm 1 mm 0.5 mm -

0.05 mm 5 mm 1 mm voxels 5 mm

Pattern!classification VEP ERD/

ERS P300

Performance2 class 90% 3 class 80%

4 class ?

Large number

of targets2 cls 90%

Large number

of targets8 cls 90% High*

~ same as EEG based

4 cls 90%

2 cls 90%

Technology Electrical Magnetic Optical

Name EEG ECoG Intracortical MEG fMRI fNIRS

Invasive !

Portable !

Cost From $100 to $30,000+ $1000 grid

$2000 per array $1 mln $2-3

mln $200,000

Temporal resolution 50 ms 3 ms 3 ms 50ms 1-2 s 1 s

Spatial resolution 1+ cm 1 mm 0.5 mm -

0.05 mm 5 mm 1 mm voxels 5 mm

Pattern!classification VEP ERD/

ERS P300

Performance2 class 90% 3 class 80%

4 class ?

Large number

of targets2 cls 90%

Large number

of targets8 cls 90% High*

~ same as EEG based

4 cls 90%

2 cls 90%

Neuroimaging: Intracortical, fMRI, EEG

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