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Measured Signal. Neuronal Activation. ?. ?. ?. ?. Hemodynamics. Noise. Dynamics Fluctuations Pattern Information Neuronal Current MRI. The BOLD Signal. B lood O xygenation L evel D ependent (BOLD) signal changes. task. task.

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slide1

Measured Signal

Neuronal Activation

?

?

?

?

Hemodynamics

Noise

slide2

Dynamics

  • Fluctuations
  • Pattern Information
  • Neuronal Current MRI
slide3

The BOLD Signal

Blood Oxygenation Level Dependent (BOLD) signal changes

task

task

slide4

Brief “off” periods produce smaller decreases than expected.

measured

2

1.5

0

linear

Signal (%)

1

Linearity

-2

measured

0.5

linear

-4

0

0

5

10

15

20

time (s)

Stimulus OFF duration (s)

R.M. Birn, P. A. Bandettini, NeuroImage, 27, 70-82 (2005)

Brief “on” periods produce larger increases than expected.

measured

linear

3

Linearity

2

Signal

linear

1

0

1

2

3

4

5

time (s)

Stimulus Duration (s)

R. M. Birn, Z. Saad, P. A. Bandettini, NeuroImage, 14: 817-826, (2001)

slide5

MEG & fMRI Linearity Comparison

A. Tuan, R. M. Birn, P. A. Bandettini, G. M. Boynton, (submitted)

slide6

MEG

Results

  • Tuan, R. M. Birn, P. A. Bandettini, G. M. Boynton,
  • International Journal of Imaging Systems and Technology 18, 17-28 (2008)
slide7

Measured and Predicted BOLD responses

Non-linearity computed from MEG prediction

3

0s ramp

0.5s ramp

1s ramp

Non-linearity

2

1

0

5

10

15

Stimulus Duration

Non-linearity computed from BOLD

3

Non-linearity

2

1

0

5

10

15

Stimulus Duration (s)

BOLDMEG

  • Tuan, R. M. Birn, P. A. Bandettini, G. M. Boynton,
  • International Journal of Imaging Systems and Technology 18, 17-28 (2008)
slide8

Dynamics

  • Fluctuations
  • Pattern Information
  • Neuronal Current MRI
slide9

Resting State Correlations

Activation:

correlation with reference function

Rest:

seed voxel in motor cortex

B. Biswal et al., MRM, 34:537 (1995)

slide10

Sources of time series fluctuations:

  • Blood, brain and CSF pulsation
  • Vasomotion
  • Breathing cycle (B0 shifts with lung expansion)
  • Bulk motion
  • Scanner instabilities
  • Changes in blood CO2 (changes in breathing)
  • Spontaneous neuronal activity
breath holding

5

Z

0

5 %

Breath-holding

Group Maps (N = 7)

MR Signal

Respiration

Cue

time (s)

0

50

100

150

200

250

300

350

Breath-hold response (average Z-score)

Anatomy

R.M. Birn, J. A. Diamond, M. A. Smith, P. A. Bandettini, NeuroImage, 31, 1536-1548

slide12

50

100

150

200

250

300

350

1

0.5

CC

2

0

CO2

0

50

100

150

200

250

300

350

-0.5

RVT

-20

-10

0

10

time (s)

0

Shift (s)

0

50

100

150

200

250

T

max

min

300

310

315

305

time (s)

max - min

RVT =

T

Estimating respiration volume changes

Respiration

time (s)

Respiration Volume / Time (RVT)

RVT precedes end tidal CO2 by 5 sec.

respiration induced signal changes

0

BOLD

Z

Respiration

Cue

0

100

200

300

Time (sec)

-4

5

Z

BOLD

Respiration

RVT

0

0

100

200

300

Time (sec)

Respiration induced signal changes

Rest

Breath-holding

(N=7)

R.M. Birn, J. A. Diamond, M. A. Smith, P. A. Bandettini, NeuroImage, 31, 1536-1548 (2006)

slide14

Resting state correlation with

signal from posterior cingulate

Resting state correlation with

RVT signal

10

6

|Z|

Z

0

-10

RVT Correlation Maps &Functional Connectivity Maps

Group (n=10)

R.M. Birn, J. A. Diamond, M. A. Smith, P. A. Bandettini, NeuroImage, 31, 1536-1548 (2006)

slide15

Effect of Respiration Rate Consistency on Resting Correlation Maps

Spontaneously Varying Respiration Rate

Constant Respiration Rate

10

10

Z

Z

-10

-10

Group (n=10)

R.M. Birn, J. A. Diamond, M. A. Smith, P. A. Bandettini, NeuroImage, 31, 1536-1548 (2006)

slide17

Temporal Signal to Noise Ratio (TSNR) vs. Signal to Noise Ratio (SNR)

J. Bodurka, F. Ye, N Petridou, K. Murphy, P. A. Bandettini, NeuroImage, 34, 542-549 (2007)

slide18

Sensitivity, Scan Time, and Temporal Signal to Noise

K. Murphy, J. Bodurka, P. A. Bandettini, NeuroImage, 34, 565-574 (2007)

multi sensory integration
Multi-sensory integration

M.S. Beauchamp et al.,

Visual

Auditory

Multisensory

slide21

Dynamics

  • Fluctuations
  • Pattern Information
  • Neuronal Current MRI
slide22

Pattern Information

Mapping

“searchlight” ROI

N. Kriegeskorte, R. Goebel, P. Bandettini, Proc. Nat\'l. Acad. Sci. USA, 103, 3863-3868 (2006)

From fixed ROI

slide23

96

0

0

0

0

0

0

dissimilarity

matrix

96

0

0

0

0

0

0

96

Dissimilarity Matrix

Creation

compute dissimilarity

(1-correlation across space)

response

patterns

...

ROI in Brain

stimuli

...

N. Kriegeskorte, et al, Neuron (in press)

slide25

Human Early Visual Cortex(1057 visually most responsive voxels)

Human IT(1000 visually most responsive voxels)

monkey human comparison procedure
Human

fMRI in four subjects(repeated sessions,>12 runs per subject)

"quick" event-related design(stimulus duration: 300ms,stimulus onset asynchrony: 4s)

fixation task(with discrimination of fixation-point color changes)

occipitotemporal measurement slab(5-cm thick)

small voxels (1.951.952mm3)

3T magnet, 16-channel coil (SENSE, acc. fac. 2)

Monkey (Kiani et al. 2007)

single-cell recordingsin two monkeys

rapid serial presentation(stimulus duration: 105ms)

fixation task

electrodes in anterior IT(left in monkey 1, right in monkey 2)

674 cells total

windowed spike count(140-ms window starting 71ms after stimulus onset)

Monkey-Human Comparison Procedure
slide27

average of 4 subjects

fixation-color task

316 voxels

average of 2 monkeys

fixation task

>600 cells

N. Kriegeskorte, et al Neuron (in press)

slide28

Dynamics

  • Fluctuations
  • Pattern Information
  • Neuronal Current MRI
slide29

Magnetic Field

Intracellular

Current

Surface Fields

100 fT at on the scalp

J.P. Wikswo Jr et al. J Clin Neuronphy 8(2): 170-188, 1991

slide30

Surface Field Distribution Across Spatial Scales

Adapted from: J.P. Wikswo Jr et al.

J Clin Neurophy 8(2): 170-188, 1991

slide31

Magnetic field associated with a bundle of dendrites

Because BMEG=100fTis measured by MEG on the scalp

at least50,000 neurons(0.002 fT (per dendrite) x 50,000 = 100 fT), must coherently act to generate such field. These bundles of neurons produce, within a typical voxel, 1 mm x 1 mm x 1 mm, a field of order:

BMRI0.2nT

slide32

B0

calculated Bc ||B0

Measurement

70 A current



 200

Single shot GE EPI

Correlation image

J. Bodurka, P. A. Bandettini. Magn. Reson. Med. 47: 1052-1058, (2002).

slide33

Cortex

Basal

Ganglia

100 mm

Plenz, D. et al. Neurosci 70(4): 861-924, 1996

in vitro model

Organotypic (no blood supply or hemoglobin traces) sections of newborn-rat somato-sensory Cortex &Basal Ganglia

  • Size: in-plane:~1-2mm2, thickness: 60-100m
  • Neuronal Population: 10,000-100,000
  • Spontaneous synchronized activity < 2Hz
  • Epileptiform activity
  • Spontaneous beta freq. activity (20-30Hz)
  • Network Activity Range: ~ 0.5-15V
slide34

1: culture

2: ACSF

ACSF

Culture

C

C

A

A

B

B

FSE image

Hz

Hz

0.15Hz map

1

2

3 Tesla data

Active condition: black line

Inactive condition: red line

A: 0.15 Hz activity, on/off frequency

B: activity

C: scanner noise (cooling-pump)

slide35

7 Tesla data

TTX

Power decrease between PRE & TTX EEG : ~ 81%

Decrease between PRE & TTX MR phase: ~ 70%

Decrease between PRE & TTX MR magnitude: ~ 8%

N. Petridou, D. Plenz, A. C. Silva, J. Bodurka, M. Loew, P. A. Bandettini, Proc. Nat\'l. Acad. Sci. USA. 103, 16015-16020 (2006).

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