Neurophysiology and BOLD
David C. Zhu, Ph.D.
C
Cognitive
iti Imaging
I
i Research
R
h Center
C t
Departments of Psychology and Radiology
Reading materials:
Chapters 6 and 7
From MSU 3T scanner
Huettel SA, Song AW, McCarthy G. Functional Magnetic Resonance Imaging.
Explanation of T2* decay
di
diamagnetic
ti
3.000 T
3.000 T
3.000 T
3.000 T
3+10-6 T
3.000 T
3+2×10-6 T
3-10-6 T
After
30 ms
oxygenated
t d hemoglobin
h
l bi
3.000 T
3.000 T
3.000 T
3.000 T
Vector
sum
deoxygenated hemoglobin
paramagnetic
Af
After
Vector
30 ms 3+10-6 T
sum
3.000 T
3+2×10-6 T
3-10-6 T
Two Main Paths
First 1-2 seconds
Later seconds
Stimulation
Neuronal Activity
CMRglucose
CMRO2
Blood Oxygen Level
Deoxygenated hemoglobin: paramagnetic
Blood Magnetic
g
Susceptibility Effects
Cerebral Blood
Flow (CBF)
Blood Oxygen Level
Oxygenated hemoglobin: diamagnetic
Blood Magnetic
g
Susceptibility Effects
T2* decay
T2* decay
fMRI Image Signal Intensity
fMRI Image Signal Intensity
Mechanisms of BOLD (Blood Oxygen LevelLevel-Dependent) fMRI
Stimulation
Neuronal Activity
+
CMRglucose
+
CMRO2
+
+
+
-
Cerebral Blood
Volume (CBV)
Blood Oxygen Level
+
Cerebral Blood
Flow (CBF)
-
+
+
In Flow Effect
Blood Magnetic
Susceptibility Effects
+
1/T2*
+
Oxygenated hemoglobin: diamagnetic
Deoxygenated hemoglobin: paramagnetic
+
1/T1
-
+
fMRI Image Signal Intensity
Springer CS Jr, Patlak CS, Palyka I and Huang W. “Principles of susceptibility contrast-based functional MRI: …
Oxygenated hemoglobin:
diamagnetic
D
Deoxygenated
t dh
hemoglobin:
l bi
paramagnetic
Huettel SA, Song AW, McCarthy G. Functional Magnetic Resonance Imaging.
A single short-duration event
A block of multiple
consecutive events
30 slices
Slice #30
Slice #1
Slice #3
Sli #2
Slice
Slice #29
2 sec = TR
2 sec
Repeat
many
times
ti
2 sec
2 sec
Bimanual finger tapping motor study (P ≤ 10-7)
(12 s resting and then 24 s finger tapping at 1 Hz, TR = 2 s)